Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 747
Filtrar
1.
Am J Physiol Heart Circ Physiol ; 317(4): H754-H764, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31373511

RESUMO

What strategies are employed by the sympathetic system to communicate with the circulation? Muscle sympathetic nerve activity (MSNA) occurs in bursts of synchronous action potential (AP) discharge, yet whether between-burst asynchronous AP firing exists remains unknown. Using multiunit microneurography and a continuous wavelet transform to isolate APs, we studied AP synchronicity within human MSNA. Asynchronous APs were defined as those which occurred between bursts. Experiment 1 quantified AP synchronicity in eight individuals at baseline (BSL), -10 mmHg lower body negative pressure (LBNP), -40 mmHg LBNP, and end-expiratory apnea (APN). At BSL, 33 ± 12% of total AP activity was asynchronous. Asynchronous discharge was unchanged from BSL (67 ± 37 AP/min) to -10 mmHg LBNP (69 ± 33 AP/min), -40 mmHg LBNP (83 ± 68 AP/min), or APN (62 ± 39 AP/min). Across all conditions, asynchronous AP probability and frequency decreased with increasing AP size. Experiment 2 examined the impact of the ganglia on AP synchronicity by using nicotinic blockade (trimethaphan). The largest asynchronous APs were derecruited from BSL (11 ± 4 asynchronous AP clusters) to the last minute of the trimethaphan infusion with visible bursts (7 ± 2 asynchronous AP clusters). However, the 6 ± 2 smallest asynchronous AP clusters could not be blocked by trimethaphan and persisted to fire 100 ± 0% asynchronously without forming bursts. Nonnicotinic ganglionic mechanisms affect some, but not all, asynchronous activity. The fundamental behavior of human MSNA contains between-burst asynchronous AP discharge, which accounts for a considerable amount of BSL activity.NEW & NOTEWORTHY Historically, sympathetic nerve activity destined for the blood vessels supplying skeletal muscle (MSNA) has been characterized by spontaneous bursts formed by synchronous action potential (AP) discharge. However, this study found a considerable amount (~30% during baseline) of sympathetic AP discharge to fire asynchronously between bursts of human MSNA. Trimethaphan infusion revealed that nonnicotinic ganglionic mechanisms contribute to some, but not all, asynchronous discharge. Asynchronous sympathetic AP discharge represents a fundamental behavior of MSNA.


Assuntos
Potenciais de Ação , Vasos Sanguíneos/inervação , Músculo Esquelético/irrigação sanguínea , Sistema Nervoso Simpático/fisiologia , Potenciais de Ação/efeitos dos fármacos , Adulto , Apneia/fisiopatologia , Barorreflexo , Feminino , Bloqueadores Ganglionares/farmacologia , Humanos , Pressão Negativa da Região Corporal Inferior , Masculino , Antagonistas Nicotínicos/farmacologia , Sistema Nervoso Simpático/efeitos dos fármacos , Fatores de Tempo , Trimetafano/farmacologia , Adulto Jovem
2.
Hypertension ; 72(5): 1236-1242, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30354803

RESUMO

Autonomic support of blood pressure increases with age in humans. Large differences exist in the dose of trimethaphan (TMP) required for ganglionic blockade in young and older women. We asked whether differences in the dose of TMP required to achieve ganglionic blockade are because of differences in the relative contributions of the sympathetic and parasympathetic nervous system in control of blood pressure with age. Muscle sympathetic nerve activity (microneurography, peroneal nerve), heart rate (HR), and blood pressure were recorded before and during incremental doses of TMP camsylate until ganglionic blockade was achieved (absence of muscle sympathetic nerve activity and <5-bpm increase in HR during a valsalva maneuver; final TMP dose, 1-7 mg/min). HR variability was analyzed from the ECG waveform (WinCPRS). The dose of TMP required to achieve ganglionic blockade is positively related to basal HR variability, where women with high HR variability require a higher dose of TMP to achieve ganglionic blockade. In contrast, baseline muscle sympathetic nerve activity is inversely related with the dose of TMP required to achieve ganglionic blockade, such that women with high basal muscle sympathetic nerve activity required a lower dose of TMP. As such, the change in HR with ganglionic blockade was positively related, and the change in mean arterial pressure was inversely related, with the dose of TMP required to achieve ganglionic blockade. These data suggest loss of parasympathetic tone and increased sympathetic tone with aging contribute to the increase in blood pressure with age in women and dictate the dose of TMP that is necessary to achieve ganglionic blockade.


Assuntos
Pressão Sanguínea/fisiologia , Sistema Nervoso Parassimpático/fisiologia , Sistema Nervoso Simpático/fisiologia , Adolescente , Adulto , Idoso , Pressão Sanguínea/efeitos dos fármacos , Feminino , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Humanos , Pessoa de Meia-Idade , Sistema Nervoso Parassimpático/efeitos dos fármacos , Sistema Nervoso Simpático/efeitos dos fármacos , Trimetafano/farmacologia , Vasodilatadores/farmacologia , Adulto Jovem
3.
J Physiol ; 596(18): 4497-4510, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-30054928

RESUMO

KEY POINTS: The mechanisms affecting recruitment patterns of postganglionic sympathetic nerves remain unclear. The divergent and convergent preganglionic innervation patterns of postganglionic neurons and the presence of differently sized postganglionic nerves suggest that the ganglia may participate in modifying the discharge patterns of single sympathetic postganglionic neurons innervating the skeletal muscle circulation. Whether the ganglia affect the ordered behaviour of varying sized postganglionic sympathetic neurons in humans has not been studied. Trimethaphan infusion produced an ordered pattern of action potential (AP) de-recruitment whereby the firing of larger, low probability APs present at baseline was abolished first, followed by progressive decreased probability of smaller APs. Although integrated sympathetic bursts were no longer detected after several minutes of trimethaphan, firing of the smallest APs was detected. These data suggest the ganglia affect the distribution of firing probabilities exhibited by differently sized sympathetic neurons. The ganglia may contribute to sympathetic neural emission patterns involved in homeostatic regulation. ABSTRACT: Do the ganglia contribute to the ordered behaviour of postganglionic neuronal discharge within the sympathetic nervous system? To further understand the functional organization of the sympathetic nervous system we employed the microneurographic approach to record muscle sympathetic nerve activity (MSNA) and a continuous wavelet transform to study postganglionic action potential (AP) behaviour during nicotinic blockade at the ganglia (trimethaphan camsylate, 1-7 mg min-1 ) in seven females (37 ± 5 years). Trimethaphan elicited a progressive reduction in sympathetic outflow characterized by fewer integrated bursts with decaying amplitude. Underlying trimethaphan-mediated attenuations in integrated MSNA were reductions in AP incidence (186 ± 101 to 29 ± 31 AP (100 beats)-1 ) and AP content per integrated burst (7 ± 2 to 3 ± 1 APs burst-1 ) (both P < 0.01) in the final minute of detectable bursting activity in the trimethaphan condition, compared to baseline. We observed an ordered de-recruitment of larger to smaller AP clusters active at baseline (14 ± 3 to 8 ± 2 active AP clusters, P < 0.01). Following cessation of integrated bursts in the trimethaphan condition, the smallest 6 ± 2 sympathetic AP clusters persisted to fire in an asynchronous pattern (49 ± 41 AP (100 beats)-1 ) in all participants. Valsalva's manoeuvre did not increase the incidence of these persistent APs (60 ± 42 AP (100 beats)-1 , P = 0.52), or recruit any larger APs in six of seven participants (6 ± 1 total AP clusters, P = 0.30). These data suggest that the ganglia participate in the ordered recruitment of differently sized postganglionic sympathetic nerves.


Assuntos
Potenciais de Ação , Fibras Simpáticas Pós-Ganglionares/fisiologia , Adulto , Feminino , Bloqueadores Ganglionares/farmacologia , Humanos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Recrutamento Neurofisiológico , Fibras Simpáticas Pós-Ganglionares/citologia , Fibras Simpáticas Pós-Ganglionares/efeitos dos fármacos , Trimetafano/farmacologia
4.
Clin Auton Res ; 27(3): 157-165, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28205011

RESUMO

PURPOSE: The blood pressure "error signal" represents the difference between an individual's mean diastolic blood pressure and the diastolic blood pressure at which 50% of cardiac cycles are associated with a muscle sympathetic nerve activity burst (the "T50"). In this study we evaluated whether T50 and the error signal related to the extent of change in blood pressure during autonomic blockade in young and older women, to study potential differences in sympathetic neural mechanisms regulating blood pressure before and after menopause. METHODS: We measured muscle sympathetic nerve activity and blood pressure in 12 premenopausal (25 ± 1 years) and 12 postmenopausal women (61 ± 2 years) before and during complete autonomic blockade with trimethaphan camsylate. RESULTS: At baseline, young women had a negative error signal (-8 ± 1 versus 2 ± 1 mmHg, p < 0.001; respectively) and lower muscle sympathetic nerve activity (15 ± 1 versus 33 ± 3 bursts/min, p < 0.001; respectively) than older women. The change in diastolic blood pressure after autonomic blockade was associated with baseline T50 in older women (r = -0.725, p = 0.008) but not in young women (r = -0.337, p = 0.29). Women with the most negative error signal had the lowest muscle sympathetic nerve activity in both groups (young: r = 0.886, p < 0.001; older: r = 0.870, p < 0.001). CONCLUSIONS: Our results suggest that there are differences in baroreflex control of muscle sympathetic nerve activity between young and older women, using the T50 and error signal analysis. This approach provides further information on autonomic control of blood pressure in women.


Assuntos
Envelhecimento/fisiologia , Pressão Sanguínea/fisiologia , Sistema Nervoso Simpático/fisiologia , Adulto , Idoso , Fármacos do Sistema Nervoso Autônomo/farmacologia , Barorreflexo/efeitos dos fármacos , Barorreflexo/fisiologia , Pressão Sanguínea/efeitos dos fármacos , Feminino , Bloqueadores Ganglionares/farmacologia , Hemodinâmica/efeitos dos fármacos , Hemodinâmica/fisiologia , Humanos , Menopausa/fisiologia , Pessoa de Meia-Idade , Músculo Esquelético/inervação , Músculo Esquelético/fisiologia , Pós-Menopausa/fisiologia , Pré-Menopausa/fisiologia , Sistema Nervoso Simpático/efeitos dos fármacos , Trimetafano/farmacologia , Vasodilatadores/farmacologia , Adulto Jovem
5.
Am J Physiol Heart Circ Physiol ; 312(2): H340-H346, 2017 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-27923789

RESUMO

Central (aortic) blood pressure, arterial stiffness, and sympathetic nerve activity increase with age in women. However, it is unknown if the age-related increase in sympathetic activity influences aortic hemodynamics and carotid-femoral pulse wave velocity (cfPWV), an index of central aortic stiffness. The goal of this study was to determine if aortic hemodynamics and cfPWV are directly influenced by sympathetic nerve activity by measuring aortic hemodynamics, cfPWV, and muscle sympathetic nerve activity (MSNA) in women before and during autonomic ganglionic blockade with trimethaphan camsylate. We studied 12 young premenopausal (23 ± 4 yr) and 12 older postmenopausal (57 ± 3 yr) women. These women did not differ in body mass index or mean arterial pressure (P > 0.05 for both). At baseline, postmenopausal women had higher aortic pulse pressure, augmented pressure, augmentation index adjusted for a heart rate of 75 beats/min, wasted left ventricular pressure energy, and cfPWV than young women (P < 0.05). During ganglionic blockade, postmenopausal women had a greater decrease in these variables in comparison to young women (P < 0.05). Additionally, baseline MSNA was negatively correlated with the reductions in aortic pulse pressure, augmented pressure, and wasted left ventricular pressure energy during ganglionic blockade in postmenopausal women (P < 0.05) but not young women. Baseline MSNA was not correlated with the changes in augmentation index adjusted for a heart rate of 75 beats/min or cfPWV in either group (P > 0.05 for all). Our results suggest that some aortic hemodynamic parameters are influenced by sympathetic activity to a greater extent in older postmenopausal women than in young premenopausal women.NEW & NOTEWORTHY Autonomic ganglionic blockade results in significant decreases in multiple aortic pulse wave characteristics (e.g., augmented pressure) and central pulse wave velocity in older postmenopausal women but not in young premenopausal women. Certain aortic pulse wave parameters are negatively influenced by sympathetic activity to a greater extent in older postmenopausal women.


Assuntos
Envelhecimento/fisiologia , Aorta/efeitos dos fármacos , Pressão Arterial/efeitos dos fármacos , Bloqueadores Ganglionares/farmacologia , Hemodinâmica/efeitos dos fármacos , Análise de Onda de Pulso , Sistema Nervoso Simpático/efeitos dos fármacos , Trimetafano/farmacologia , Adulto , Aorta/inervação , Aorta/fisiologia , Pressão Arterial/fisiologia , Feminino , Gânglios Autônomos , Frequência Cardíaca , Hemodinâmica/fisiologia , Humanos , Infusões Intravenosas , Pessoa de Meia-Idade , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/inervação , Pós-Menopausa , Pré-Menopausa , Sistema Nervoso Simpático/fisiologia , Rigidez Vascular/fisiologia , Vasodilatadores/farmacologia , Função Ventricular Esquerda , Pressão Ventricular/efeitos dos fármacos , Pressão Ventricular/fisiologia , Adulto Jovem
6.
Clin Auton Res ; 25(1): 53-9, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25757803

RESUMO

Despite similarities in their clinical presentation, patients with multiple system atrophy (MSA) have residual sympathetic tone and intact post-ganglionic noradrenergic fibers, whereas patients with pure autonomic failure (PAF) and Parkinson disease have efferent post-ganglionic autonomic denervation. These differences are apparent biochemically, as well as in neurophysiological testing, with near normal plasma norephrine in MSA but very low levels in PAF. These differences are also reflected in the response patients have to drugs that interact with the autonomic nervous system. For example, the ganglionic blocker trimethaphan reduces residual sympathetic tone and lowers blood pressure in MSA, but less so in PAF. Conversely, the α2-antagonist yohimbine produces a greater increase in blood pressure in MSA compared to PAF, although significant overlap exists. In normal subjects, the norepinephrine reuptake (NET) inhibitor atomoxetine has little effect on blood pressure because the peripheral effects of NET inhibition that result in noradrenergic vasoconstriction are counteracted by the increase in brain norepinephrine, which reduces sympathetic outflow (a clonidine-like effect). In patients with autonomic failure and intact peripheral noradrenergic fibers, only the peripheral vasoconstriction is apparent. This translates to a significant pressor effect of atomoxetine in MSA, but not in PAF patients. Thus, pharmacological probes can be used to understand the pathophysiology of the different forms of autonomic failure, assist in the diagnosis, and aid in the management of orthostatic hypotension.


Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Tratamento Farmacológico/métodos , Tratamento Farmacológico/tendências , Atrofia de Múltiplos Sistemas/tratamento farmacológico , Atrofia de Múltiplos Sistemas/fisiopatologia , Cloridrato de Atomoxetina/farmacologia , Cloridrato de Atomoxetina/uso terapêutico , Sistema Nervoso Autônomo/efeitos dos fármacos , Clonidina/farmacologia , Clonidina/uso terapêutico , Diagnóstico Diferencial , Humanos , Alcaloides Indólicos/farmacologia , Alcaloides Indólicos/uso terapêutico , Atrofia de Múltiplos Sistemas/diagnóstico , Doença de Parkinson/diagnóstico , Doença de Parkinson/tratamento farmacológico , Doença de Parkinson/fisiopatologia , Insuficiência Autonômica Pura/diagnóstico , Insuficiência Autonômica Pura/tratamento farmacológico , Insuficiência Autonômica Pura/fisiopatologia , Brometo de Piridostigmina/farmacologia , Brometo de Piridostigmina/uso terapêutico , Trimetafano/farmacologia , Trimetafano/uso terapêutico
7.
Hypertension ; 64(4): 867-74, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-25001269

RESUMO

Obesity is an important risk factor for the development of insulin resistance. Initial compensatory mechanisms include an increase in insulin levels, which are thought to induce sympathetic activation in an attempt to restore energy balance. We have previously shown, however, that sympathetic activity has no beneficial effect on resting energy expenditure in obesity. On the contrary, we hypothesize that sympathetic activation contributes to insulin resistance. To test this hypothesis, we determined insulin sensitivity using a standard hyperinsulinemic euglycemic clamp protocol in obese subjects randomly assigned in a crossover design 1 month apart to receive saline (intact day) or trimetaphan (4 mg/min IV, autonomic blocked day). Whole-body glucose uptake (MBW in mg/kg per minute) was used as index of maximal muscle glucose use. During autonomic blockade, we clamped blood pressure with a concomitant titrated intravenous infusion of the nitric oxide synthase inhibitor N-monomethyl-L-arginine. Of the 21 obese subjects (43±2 years; 35±2 kg/m(2) body mass index) studied, 14 were insulin resistant; they were more obese, had higher plasma glucose and insulin, and had higher muscle sympathetic nerve activity (23.3±1.5 versus 17.2±2.1 burst/min; P=0.03) when compared with insulin-sensitive subjects. Glucose use improved during autonomic blockade in insulin-resistant subjects (MBW 3.8±0.3 blocked versus 3.1±0.3 mg/kg per minute intact; P=0.025), with no effect in the insulin-sensitive group. These findings support the concept that sympathetic activation contributes to insulin resistance in obesity and may result in a feedback loop whereby the compensatory increase in insulin levels contributes to greater sympathetic activation.


Assuntos
Sistema Nervoso Autônomo/efeitos dos fármacos , Bloqueadores Ganglionares/farmacologia , Resistência à Insulina/fisiologia , Obesidade/fisiopatologia , Trimetafano/farmacologia , Adulto , Sistema Nervoso Autônomo/fisiopatologia , Glicemia/metabolismo , Pressão Sanguínea/efeitos dos fármacos , Estudos Cross-Over , Inibidores Enzimáticos/farmacologia , Feminino , Técnica Clamp de Glucose/métodos , Humanos , Insulina/administração & dosagem , Insulina/sangue , Masculino , Pessoa de Meia-Idade , Músculos/inervação , Óxido Nítrico Sintase/antagonistas & inibidores , Óxido Nítrico Sintase/metabolismo , Obesidade/sangue , ômega-N-Metilarginina/farmacologia
8.
Hypertension ; 63(2): 303-8, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24324040

RESUMO

The autonomic nervous system plays a central role in both acute and chronic blood pressure regulation in humans. The activity of the sympathetic branch of the autonomic nervous system is positively associated with peripheral resistance, an important determinant of mean arterial pressure in men. In contrast, there is no association between sympathetic nerve activity and peripheral resistance in women before menopause, yet a positive association after menopause. We hypothesized that autonomic support of blood pressure is higher after menopause in women. We examined the effect of ganglionic blockade on arterial blood pressure and how this relates to baseline muscle sympathetic nerve activity in 12 young (25±1 years) and 12 older postmenopausal (61±2 years) women. The women were studied before and during autonomic blockade using trimethaphan camsylate. At baseline, muscle sympathetic nerve activity burst frequency and burst incidence were higher in the older women (33±3 versus 15±1 bursts/min; 57±5 versus 25±2 bursts/100 heartbeats, respectively; P<0.05). Muscle sympathetic nerve activity bursts were abolished by trimethaphan within minutes. Older women had a greater decrease in mean arterial pressure (-29±2 versus -9±2 mm Hg; P<0.01) and total peripheral resistance (-10±1 versus -5±1 mm Hg/L per minute; P<0.01) during trimethaphan. Baseline muscle sympathetic nerve activity was associated with the decrease in mean arterial pressure during trimethaphan (r=-0.74; P<0.05). In summary, our results suggest that autonomic support of blood pressure is greater in older women compared with young women and that elevated sympathetic nerve activity in older women contributes importantly to the increased incidence of hypertension after menopause.


Assuntos
Envelhecimento/fisiologia , Pressão Sanguínea/fisiologia , Hipertensão/fisiopatologia , Sistema Nervoso Simpático/fisiologia , Resistência Vascular/fisiologia , Adulto , Pressão Sanguínea/efeitos dos fármacos , Artéria Braquial/inervação , Artéria Braquial/fisiologia , Feminino , Bloqueadores Ganglionares/administração & dosagem , Humanos , Menopausa/fisiologia , Pessoa de Meia-Idade , Músculo Esquelético/inervação , Músculo Esquelético/fisiologia , Nervo Fibular/fisiologia , Sistema Nervoso Simpático/efeitos dos fármacos , Trimetafano/administração & dosagem , Resistência Vascular/efeitos dos fármacos , Vasodilatadores/administração & dosagem , Adulto Jovem
9.
Am J Physiol Heart Circ Physiol ; 302(7): H1438-43, 2012 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-22287587

RESUMO

The purpose of this study was to determine if tonic restrain of blood pressure by nitric oxide (NO) is impaired early in the development of hypertension. Impaired NO function is thought to contribute to hypertension, but it is not clear if this is explained by direct effects of NO on vascular tone or indirect modulation of sympathetic activity. We determined the blood pressure effect of NO synthase inhibition with N(ω)-monomethyl-l-arginine (L-NMMA) during autonomic blockade with trimethaphan to eliminate baroreflex buffering and NO modulation of autonomic tone. In this setting, impaired NO modulation of vascular tone would be reflected as a blunted pressor response to L-NMMA. We enrolled a total of 66 subjects (39 ± 1.3 yr old, 30 females), 20 normotensives, 20 prehypertensives (blood pressure between 120/80 and 140/90 mmHg), 17 hypertensives, and 9 smokers (included as "positive" controls of impaired NO function). Trimethaphan normalized blood pressure in hypertensives, suggesting increased sympathetic tone contributing to hypertension. In contrast, L-NMMA produced similar increases in systolic blood pressure in normal, prehypertensive, and hypertensive subjects (31 ± 2, 32 ± 2, and 30 ± 3 mmHg, respectively), whereas the response of smokers was blunted (16 ± 5 mmHg, P = 0.012). Our results suggest that sympathetic activity plays a role in hypertension. NO tonically restrains blood pressure by ∼30 mmHg, but we found no evidence of impaired modulation by NO of vascular tone contributing to the early development of hypertension. If NO deficiency contributes to hypertension, it is likely to be through its modulation of the autonomic nervous system, which was excluded in this study.


Assuntos
Hipertensão/fisiopatologia , Óxido Nítrico/fisiologia , Sistema Nervoso Simpático/fisiopatologia , Adolescente , Adulto , Envelhecimento/fisiologia , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Inibidores Enzimáticos/farmacologia , Feminino , Frequência Cardíaca/efeitos dos fármacos , Humanos , Masculino , Pessoa de Meia-Idade , Tono Muscular/efeitos dos fármacos , Tono Muscular/fisiologia , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/fisiologia , Antagonistas Nicotínicos/farmacologia , Óxido Nítrico Sintase Tipo III/antagonistas & inibidores , Receptores Nicotínicos/efeitos dos fármacos , Fumar/fisiopatologia , Sistema Nervoso Simpático/efeitos dos fármacos , Trimetafano/farmacologia , Adulto Jovem , ômega-N-Metilarginina/farmacologia
10.
Chin Med J (Engl) ; 124(3): 413-8, 2011 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21362343

RESUMO

BACKGROUND: The neurogenic bladder dysfunction caused by spinal cord injury is difficult to treat clinically. The aim of this research was to establish an artificial bladder reflex arc in rats through abdominal reflex pathway above the level of spinal cord injury, reinnervate the neurogenic bladder and restore bladder micturition. METHODS: The outcome was achieved by intradural microanastomosis of the right T13 ventral root to S2 ventral root with autogenous nerve grafting, leaving the right T13 dorsal root intact. Long-term function of the reflex arc was assessed from nerve electrophysiological data and intravesical pressure tests during 8 months postoperation. Horseradish peroxidase (HRP) tracing was performed to observe the effectiveness of the artificial reflex. RESULTS: Single stimulus (3 mA, 0.3 ms pulses, 20 Hz, 5-second duration) on the right T13 dorsal root resulted in evoked action potentials, raised intravesical pressures and bladder smooth muscle, compound action potential recorded from the right vesical plexus before and after the spinal cord transaction injury between L5 and S4 segmental in 12 Sprague-Dawley rats. There were HRP labelled cells in T13 ventral horn on the experimental side and in the intermediolateral nucleus on both sides of the L6-S4 segments after HRP injection. There was no HRP labelled cell in T13 ventral horn on the control side. CONCLUSION: Using the surviving somatic reflex above the level of spinal cord injury to reconstruct the bladder autonomous reflex arc by intradural microanastomosis of ventral root with a segment of autologous nerve grafting is practical in rats and may have clinical applications for humans.


Assuntos
Reflexo Abdominal/fisiologia , Bexiga Urinaria Neurogênica/fisiopatologia , Anastomose Cirúrgica , Animais , Atropina/farmacologia , Masculino , Modelos Teóricos , Ratos , Ratos Sprague-Dawley , Reflexo Abdominal/efeitos dos fármacos , Trimetafano/farmacologia
11.
J Physiol ; 588(Pt 14): 2669-78, 2010 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-20519311

RESUMO

Regional infusions of beta(2)-adrenoceptor (ADRB2) agonist have generally shown that individuals homozygous for Gly16 produces greater vasodilatation than those homozygous for Arg16. Systemic infusions have shown an opposite effect on systemic vascular resistance (SVR), possibly confounded by baroreflexes or interactions between single nucleotide polymorphism (SNP) positions 16 and 27. We tested the hypothesis that ADRB2 gene variation would influence the SVR response to ADRB2 agonist terbutaline (Terb) during ganglionic blockade. Forty healthy young adults were recruited according to the double homozygous haplotypes: Arg16 + Gln27 (n = 13), the rare Gly16 + Gln27 (n = 6), and Gly16 + Glu27 (n = 21). Arterial pressure was measured by brachial arterial catheter, and cardiac output by acetylene breathing. Lymphocytes were sampled for ex vivo analysis of ADRB2 density and binding conformation. Following baroreflex ablation with trimethaphan (3-7 mg min(1)), continuous phenylephrine was titrated to restore blood pressure to baseline. Terb was infused i.v. at 33 and 67 ng kg(1) min(1) for 15 min/dose. There was partial evidence to suggest a main effect of haplotype on the change in SVR (P = 0.06). For SNP position 16, the highest dose of Terb produced lower SVR in Gly16 (mean +/- s.e.m.: 7.5 +/- 0.4) vs. Arg16 (8.9 +/- 0.7 units; P = 0.03). Lymphocyte ADRB2 binding conformation was similar but receptor density was greater in Gly16 vs. Arg16 (P = 0.05). We conclude that during ganglionic blockade, the SVR response to systemic ADRB2 agonist is suggestive of augmented ADRB2 function in Gly16 + Glu27 homozygotes, with greater influence from Gly16, providing further evidence that ADRB2 gene variation influences vasodilatation.


Assuntos
Receptores Adrenérgicos beta 2/genética , Receptores Adrenérgicos beta 2/fisiologia , Resistência Vascular/genética , Resistência Vascular/fisiologia , Vasodilatação/genética , Adolescente , Agonistas de Receptores Adrenérgicos beta 2 , Agonistas Adrenérgicos beta/farmacologia , Adulto , Bloqueio Nervoso Autônomo , Barorreflexo/efeitos dos fármacos , Barorreflexo/genética , Barorreflexo/fisiologia , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/genética , Pressão Sanguínea/fisiologia , Artéria Braquial/efeitos dos fármacos , Artéria Braquial/fisiologia , Débito Cardíaco/efeitos dos fármacos , Débito Cardíaco/genética , Débito Cardíaco/fisiologia , Feminino , Bloqueadores Ganglionares/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/genética , Frequência Cardíaca/fisiologia , Humanos , Masculino , Fenilefrina/farmacologia , Polimorfismo de Nucleotídeo Único , Terbutalina/farmacologia , Trimetafano/farmacologia , Resistência Vascular/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Adulto Jovem
12.
J Physiol ; 587(Pt 11): 2589-97, 2009 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-19403604

RESUMO

A novel neurochemical method was applied for studying the activity of sympathetic nerves in the human cerebral vascular system. The aim was to investigate whether noradrenaline plasma kinetic measurements made with internal jugular venous sampling reflect cerebrovascular sympathetic activity. A database was assembled of fifty-six healthy subjects in whom total body noradrenaline spillover (indicative of whole body sympathetic nervous activity), brain noradrenaline spillover and brain lipophlic noradrenaline metabolite (3,4-dihydroxyphenolglycol (DHPG) and 3-methoxy-4-hydroxyphenylglycol (MHPG)) overflow rates were measured. These measurements were also made following ganglion blockade (trimethaphan, n = 6), central sympathetic inhibition (clonidine, n = 4) and neuronal noradrenaline uptake blockade (desipramine, n = 13) and in a group of patients (n = 9) with pure autonomic failure (PAF). The mean brain noradrenline spillover and brain noradrenaline metabolite overflow in healthy subjects were 12.5 +/- 1.8, and 186.4 +/- 25 ng min(-1), respectively, with unilateral jugular venous sampling for both. Total body noradrenaline spillover was 605.8 ng min(-1) +/- 34.4 ng min(-1). As expected, trimethaphan infusion lowered brain noradrenaline spillover (P = 0.03), but perhaps surprisingly increased jugular overflow of brain metabolites (P = 0.01). Suppression of sympathetic nervous outflow with clonidine lowered brain noradrenaline spillover (P = 0.004), without changing brain metabolite overflow (P = 0.3). Neuronal noradrenaline uptake block with desipramine lowered the transcranial plasma extraction of tritiated noradrenaline (P = 0.001). The PAF patients had 77% lower brain noradrenaline spillover than healthy recruits (P = 0.06), indicating that in them sympathetic nerve degeneration extended to the cerebral circulation, but metabolites overflow was similar to healthy subjects (P = 0.3). The invariable discordance between noradrenline spillover and noradrenaline metabolite overflow from the brain under these different circumstances indicates that the two measures arise from different sources, i.e. noradrenaline spillover originates from the cerebral vasculature outside the blood-brain barrier, and the noradrenaline metabolites originate primarily from brain noradrenergic neurons. We suggest that measurements of transcranial plasma noradrenaline spillover have utility as a method for assessing the sympathetic nerve activity of the cerebral vasculature.


Assuntos
Artérias Cerebrais/inervação , Veias Cerebrais/inervação , Circulação Cerebrovascular , Veias Jugulares , Norepinefrina/sangue , Insuficiência Autonômica Pura/sangue , Sistema Nervoso Simpático/metabolismo , Inibidores da Captação Adrenérgica/farmacologia , Adulto , Biomarcadores/sangue , Estudos de Casos e Controles , Circulação Cerebrovascular/efeitos dos fármacos , Clonidina/farmacologia , Bases de Dados como Assunto , Desipramina/farmacologia , Feminino , Bloqueadores Ganglionares/farmacologia , Humanos , Cinética , Masculino , Metoxi-Hidroxifenilglicol/análogos & derivados , Metoxi-Hidroxifenilglicol/sangue , Valor Preditivo dos Testes , Insuficiência Autonômica Pura/fisiopatologia , Valores de Referência , Sistema Nervoso Simpático/efeitos dos fármacos , Simpatolíticos/farmacologia , Trimetafano/farmacologia
13.
Am J Physiol Regul Integr Comp Physiol ; 295(5): R1546-54, 2008 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-18768769

RESUMO

Endothelin (ET) type B receptors (ET(B)R) are expressed in multiple tissues and perform different functions depending on their location. ET(B)R mediate endothelium-dependent vasodilation, clearance of circulating ET, and diuretic effects; all of these should produce a fall in arterial blood pressure. However, we recently showed that chronic activation of ET(B)R in rats with the selective agonist sarafotoxin 6c (S6c) causes sustained hypertension. We have proposed that one mechanism of this effect is constriction of capacitance vessels. The current study was performed to determine whether S6c hypertension is caused by increased generation of reactive oxygen species (ROS) and/or activation of the sympathetic nervous system. The model used was continuous 5-day infusion of S6c into male Sprague-Dawley rats. No changes in superoxide anion levels in arteries and veins were found in hypertensive S6c-treated rats. However, superoxide levels were increased in sympathetic ganglia from S6c-treated rats. In addition, superoxide levels in ganglia increased progressively the longer the animals received S6c. Treatment with the antioxidant tempol impaired S6c-induced hypertension and decreased superoxide levels in ganglia. Acute ganglion blockade lowered blood pressure more in S6c-treated rats than in vehicle-treated rats. Although plasma norepinephrine levels were not increased in S6c hypertension, surgical ablation of the celiac ganglion plexus, which provides most of the sympathetic innervation to the splanchnic organs, significantly attenuated hypertension development. The results suggest that S6c-induced hypertension is partially mediated by sympathoexcitation to the splanchnic organs driven by increased oxidative stress in prevertebral sympathetic ganglia.


Assuntos
Gânglios Simpáticos/metabolismo , Hipertensão/induzido quimicamente , Hipertensão/metabolismo , Superóxidos/metabolismo , Sistema Nervoso Simpático/metabolismo , Vasoconstritores/toxicidade , Venenos de Víboras/toxicidade , Acridinas , Animais , Denervação , Etídio/análogos & derivados , Corantes Fluorescentes , Gânglios Simpáticos/fisiologia , Bloqueadores Ganglionares/farmacologia , Luminescência , Masculino , Tono Muscular/fisiologia , Músculo Liso Vascular/inervação , Músculo Liso Vascular/metabolismo , Norepinefrina/sangue , Ratos , Ratos Sprague-Dawley , Trimetafano/farmacologia
14.
Clin Pharmacol Ther ; 83(5): 692-701, 2008 May.
Artigo em Inglês | MEDLINE | ID: mdl-17687267

RESUMO

The purpose of this study was to compare ganglionic blockade with trimethaphan (TMP) and an alternative drug strategy using combined muscarinic antagonist (glycopyrrolate, GLY) and alpha-2 agonist (dexmedetomidine, DEX). Protocol 1: incremental phenylephrine was administered during control and combined GLY-DEX, or control and TMP on two control combined GLY and DEX or TMP infusion on two randomized days. Protocol 2: muscle sympathetic nerve activity (MSNA) and the baroreflex MSNA relationship was determined before and after GLY-DEX. Blood pressure was higher with GLY-DEX (99+/-3 mm Hg) and lower with TMP (78+/-3 mm Hg) relative to control (GLY-DEX: 90+/-2 mm Hg; TMP: 91+/-2 mm Hg; P<0.05). Incremental phenylephrine increased pressure during GLY-DEX (P<0.01 vs control) and TMP (P<0.01 vs control) to a similar degree. Both GLY-DEX and TMP infusion inhibited norepinephrine release (P<0.01 vs control). GLY-DEX inhibited baseline MSNA (P<0.05) and baroreflex changes in MSNA (P<0.01). We conclude that the GLY-DEX alternative drug strategy can be used as a reasonable alternative to pharmacologic ganglionic blockade to examine autonomic cardiovascular control.


Assuntos
Sistema Cardiovascular/efeitos dos fármacos , Dexmedetomidina/administração & dosagem , Bloqueadores Ganglionares/administração & dosagem , Glicopirrolato/administração & dosagem , Trimetafano/administração & dosagem , Agonistas alfa-Adrenérgicos/administração & dosagem , Adulto , Bloqueio Nervoso Autônomo/métodos , Barorreflexo/efeitos dos fármacos , Barorreflexo/fisiologia , Débito Cardíaco/efeitos dos fármacos , Sistema Cardiovascular/inervação , Catecolaminas/metabolismo , Feminino , Frequência Cardíaca/efeitos dos fármacos , Humanos , Masculino , Antagonistas Muscarínicos/administração & dosagem , Fenilefrina/administração & dosagem , Sistema Nervoso Simpático/efeitos dos fármacos
16.
J Hypertens ; 25(11): 2286-95, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17921824

RESUMO

OBJECTIVES: The causes of paroxysmal hypertension in patients in whom pheochromocytoma has been excluded ('pseudopheochromocytoma') usually remain unclear. Blood pressure disturbances and symptoms of catecholamine excess in these patients may reflect activation of the sympathetic nervous and adrenal medullary systems. We therefore examined sympathoadrenal function in patients with pseudopheochromocytoma compared with age-matched control subjects in whom there was no suspicion of pheochromocytoma. METHODS: Plasma catecholamines and hemodynamics were examined in response to intravenous glucagon, yohimbine, and trimethaphan in 11 patients with pseudopheochromocytoma and a comparison group of nine normotensive and five hypertensive volunteers. Adrenomedullary function was also assessed by abdominal F-fluorodopamine positron emission tomography and measurements of plasma metanephrine, the O-methylated metabolite of epinephrine. RESULTS: Compared with controls, patients with pseudopheochromocytoma had normal plasma concentrations of norepinephrine, but 120% higher (P < 0.05) baseline plasma concentrations of epinephrine, 80% higher (P < 0.01) baseline plasma concentrations of metanephrine, and sixfold larger (P < 0.05) increases in plasma epinephrine after glucagon. Adrenal 18F-fluorodopamine-derived radioactivity did not differ between groups. Compared with changes in plasma norepinephrine, falls in blood pressure after trimethaphan were 13-fold larger (P < 0.005) and increases in blood pressure after yohimbine were threefold larger (P < 0.01) in pseudopheochromocytoma patients than in controls. CONCLUSION: Patients with pseudopheochromocytoma exhibit a pattern of normal sympathetic noradrenergic outflow, adrenomedullary activation, and augmented blood pressure responses to changes in the sympathoneural release of norepinephrine.


Assuntos
Glândulas Suprarrenais/fisiopatologia , Hipertensão/fisiopatologia , Feocromocitoma/fisiopatologia , Sistema Nervoso Simpático/fisiopatologia , Adulto , Barorreflexo , Monitorização Ambulatorial da Pressão Arterial , Epinefrina/sangue , Feminino , Glucagon/farmacologia , Humanos , Isoproterenol/farmacologia , Masculino , Pessoa de Meia-Idade , Norepinefrina/sangue , Transtorno de Pânico/etiologia , Tomografia por Emissão de Pósitrons , Trimetafano/farmacologia , Ioimbina/farmacologia
17.
Stroke ; 38(4): 1238-44, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17332450

RESUMO

BACKGROUND AND PURPOSE: The underlying mechanisms for reductions in cerebral blood flow (CBF) during orthostasis are not completely understood. This study tested the hypothesis that sympathetic activation causes cerebral vasoconstriction leading to reductions in CBF during lower body negative pressure (LBNP). METHODS: CBF velocity, arterial pressure, and end-tidal CO(2) were measured during LBNP (-30 to -50 mm Hg) in 11 healthy subjects before and after autonomic ganglionic blockade with trimethaphan. Arterial partial pressure of CO(2) also was measured in a subgroup of 5 subjects. Mean arterial pressure during LBNP after blockade was maintained by infusion of phenylephrine. RESULTS: Before blockade, mean arterial pressure did not change during LBNP. However, CBF velocity was reduced in all subjects by 14% (P<0.05). Systolic and pulsatile (systolic-diastolic) CBF velocity were reduced by 18% and 28%, respectively, associated with significant reductions in pulse arterial pressure and end-tidal CO(2) (all P<0.05). After blockade, mean arterial pressure during LBNP was well-maintained and even increased slightly with infusion of phenylephrine. However, reductions in mean, systolic, and pulsatile CBF velocity, pulse arterial pressure, and ETCO(2) were similar to those before blockade. In contrast to reductions in end-tidal CO(2), arterial partial pressure of CO(2) did not change during LBNP. CONCLUSIONS: These data, contrary to our hypothesis, demonstrate that sympathetic vasoconstriction is not the primary mechanism underlying reductions in CBF during moderate LBNP. We speculate that diminished pulse arterial pressure or pulsatile blood flow may reduce cerebral vessel wall shear stress and contribute to reductions in CBF during orthostasis through flow mediated regulatory mechanisms.


Assuntos
Bloqueio Nervoso Autônomo/métodos , Artérias Cerebrais/fisiologia , Circulação Cerebrovascular/fisiologia , Gânglios Simpáticos/fisiologia , Postura/fisiologia , Fibras Simpáticas Pós-Ganglionares/fisiologia , Adulto , Barorreflexo/efeitos dos fármacos , Barorreflexo/fisiologia , Velocidade do Fluxo Sanguíneo/efeitos dos fármacos , Velocidade do Fluxo Sanguíneo/fisiologia , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Artérias Cerebrais/inervação , Circulação Cerebrovascular/efeitos dos fármacos , Feminino , Gânglios Simpáticos/efeitos dos fármacos , Bloqueadores Ganglionares/farmacologia , Humanos , Pressão Negativa da Região Corporal Inferior , Masculino , Fenilefrina/farmacologia , Estresse Mecânico , Volume de Ventilação Pulmonar/fisiologia , Trimetafano/farmacologia , Vasoconstrição/efeitos dos fármacos , Vasoconstrição/fisiologia , Vasoconstritores/farmacologia
18.
Clin Endocrinol (Oxf) ; 66(4): 475-82, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17371462

RESUMO

OBJECTIVE: Adipsic diabetes insipidus (DI) causes significant hypernatraemia. Morbidity and mortality data for patients with adipsic DI have been previously published as single case reports, rather than as formal trials or case series from units with established management protocols. Our objective was to describe morbidity and mortality in patients with adipsic DI attending a tertiary referral centre, representing the largest reported series of adipsic DI, and to suggest management protocols for such patients, based on our extensive experience of this condition. DESIGN: Arginine vasopressin (AVP) responses to hypotension were recorded during trimetaphan infusion. Sleep abnormalities were identified using overnight oximetry or polysomnography. Case-note analysis defined other clinical abnormalities including seizures and thrombotic episodes. Important clinical points for the management of these patients are highlighted. PATIENTS: Thirteen patients with adipsic DI defined by thirst and plasma AVP responses to hypertonic saline infusion. RESULTS: All patients had absent AVP and thirst responses to osmotic stimulation, with subnormal water intake. Five patients had absent AVP responses to hypotension; the remainder had normal responses. Eight patients were obese [body mass index (BMI) > 30 kg/m(2)], and three were overweight (BMI > 25 kg/m(2)). Seven patients had sleep apnoea, of whom three died at 36 years or younger. Four patients developed venous thrombosis during episodes of hypernatraemia. Two patients had thermoregulatory dysfunction and seven patients had seizure activity. CONCLUSION: Adipsic DI is associated with significant morbidity and mortality. Physicians should be aware of associated, treatable hypothalamic abnormalities such as obesity, sleep apnoea, seizures and thermoregulatory disorders when managing adipsic DI.


Assuntos
Diabetes Insípido , Adolescente , Adulto , Análise de Variância , Anti-Hipertensivos , Arginina Vasopressina/sangue , Arginina Vasopressina/deficiência , Regulação da Temperatura Corporal , Estudos de Casos e Controles , Diabetes Insípido/complicações , Diabetes Insípido/diagnóstico , Diabetes Insípido/metabolismo , Feminino , Humanos , Hipernatremia/metabolismo , Hipotensão/sangue , Masculino , Pessoa de Meia-Idade , Obesidade/etiologia , Obesidade/metabolismo , Adeno-Hipófise/metabolismo , Embolia Pulmonar/complicações , Embolia Pulmonar/metabolismo , Solução Salina Hipertônica , Convulsões/etiologia , Convulsões/metabolismo , Síndromes da Apneia do Sono/etiologia , Síndromes da Apneia do Sono/metabolismo , Sede , Trimetafano , Trombose Venosa/complicações , Trombose Venosa/metabolismo , Equilíbrio Hidroeletrolítico
19.
Am J Physiol Heart Circ Physiol ; 292(6): H3025-31, 2007 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-17307999

RESUMO

Cardiac beta-receptor responsiveness is diminished by both aging and hypertension. However, concomitant decreases in the activity of counterregulatory mechanisms, such as the arterial baroreflex and neuronal catecholamine uptake, influence the ultimate cardiac responses to adrenergic agents in vivo. In the present study, we evaluated by echocardiography cardiac responses to intravenous infusion of epinephrine in 14 young and 18 older normotensive men and women and in 10 young and 17 older hypertensive men and women. To assess the relative contribution of intrinsic cardiac and counterregulatory components to the overall response, infusions were repeated combined with a ganglionic blocker in the young groups. Epinephrine-induced increases in heart rate were similar in the four groups. Increases in stroke volume, ejection fraction, and cardiac index were similar in the two hypertensive and two young normotensive groups. In contrast, they were attenuated in the older normotensive group, resulting in higher left ventricular responses in older hypertensive than in normotensive subjects. Heart rate and left ventricular responses to epinephrine in the presence of ganglionic blockade did not differ between the two young groups. Increases in plasma norepinephrine due to epinephrine infusion were larger in hypertensive than in normotensive subjects. One may conclude that compared with young normotensive subjects, in hypertensive subjects mechanisms increasing versus decreasing cardiac responses to epinephrine may remain in balance, and, compared with older normotensive subjects, older hypertensive subjects exhibit enhanced cardiac responses to sympathetic stimulation.


Assuntos
Agonistas Adrenérgicos beta/administração & dosagem , Envelhecimento , Pressão Sanguínea/efeitos dos fármacos , Epinefrina/administração & dosagem , Frequência Cardíaca/efeitos dos fármacos , Hipertensão/fisiopatologia , Sistema Nervoso Simpático/efeitos dos fármacos , Função Ventricular Esquerda/efeitos dos fármacos , Agonistas Adrenérgicos beta/sangue , Adulto , Fatores Etários , Idoso , Barorreflexo/efeitos dos fármacos , Relação Dose-Resposta a Droga , Epinefrina/sangue , Feminino , Bloqueadores Ganglionares/administração & dosagem , Humanos , Hipertensão/sangue , Hipertensão/diagnóstico por imagem , Infusões Intravenosas , Masculino , Pessoa de Meia-Idade , Norepinefrina/sangue , Volume Sistólico/efeitos dos fármacos , Sistema Nervoso Simpático/fisiopatologia , Trimetafano/administração & dosagem , Ultrassonografia , Resistência Vascular/efeitos dos fármacos
20.
J Physiol ; 579(Pt 1): 215-25, 2007 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-17138611

RESUMO

The activity within the autonomic nervous system may be altered following sustained exposure to hypoxia, and it is possible that this increase in activity underlies the early acclimatization of both ventilation and the pulmonary vasculature to hypoxia. To test this hypothesis, seven individuals were infused with the ganglionic blocker trimetaphan before and after an 8 h exposure to hypoxia. The short half-life of trimetaphan should ensure that the initial infusion does not affect acclimatization to the 8 h hypoxia exposure, and the use of a ganglion blocking agent should inhibit activity within all branches of the autonomic nervous system. During the infusions of trimetaphan, measurements of ventilation and echocardiographic assessments of pulmonary vascular tone (DeltaPmax) were made during euoxia and during a short period of isocapnic hypoxia. Subjects were also studied on two control days, when a saline infusion was substituted for trimetaphan. Trimetaphan had no effect on either euoxic ventilation or the sensitivity of ventilation to acute hypoxia. Trimetaphan significantly reduced DeltaPmax in euoxia (P<0.05), but had no significant effect on the sensitivity of DeltaPmax to acute hypoxia once changes in cardiac output had been controlled for. The 8 h period of hypoxia elevated euoxic ventilation (P<0.001) and DeltaPmax (P<0.001) and increased their sensitivities to acute hypoxia (P<0.001 for both), indicating that significant acclimatization had occurred. Trimetaphan had no effect on the acclimatization response of any of these variables. We conclude that altered autonomic activity following 8 h of hypoxia does not underlie the acclimatization observed in ventilation or pulmonary vascular tone.


Assuntos
Aclimatação/fisiologia , Sistema Nervoso Autônomo/fisiologia , Hipóxia/fisiopatologia , Circulação Pulmonar/fisiologia , Mecânica Respiratória/fisiologia , Aclimatação/efeitos dos fármacos , Doença Aguda , Adulto , Sistema Nervoso Autônomo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Feminino , Bloqueadores Ganglionares/administração & dosagem , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Humanos , Masculino , Circulação Pulmonar/efeitos dos fármacos , Mecânica Respiratória/efeitos dos fármacos , Trimetafano/administração & dosagem
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...