3D reconstruction of the crural and thoracolumbar fasciae.

PURPOSE: To create computerized three-dimensional models of the crural fascia and of the superficial layer of the thoracolumbar fascia. METHODS: Serial sections of these two fasciae, stained with Azan-Mallory, van Gieson and anti-S100 antibody stains, were recorded. The resulting images were merged (Image Zone 5.0 software) and aligned (MatLab Image Processing Toolkit). Color thresholding was applied to identify the structures of interest. 3D models were obtained with Tcl/Tk scripts and Paraview 3.2.1 software. From these models, the morphometric features of these fasciae were evaluated with ImageJ. RESULTS: In the crural fascia, collagen fibers represent less than 20% of the total volume, arranged in three distinct sub-layers (mean thickness, 115 µm), separated by a layer of loose connective tissue (mean thickness, 43 µm). Inside a single sub-layer, all the fibers are parallel, whereas the angle between the fibers of adjacent layers is about 78°. Elastic fibers are less than 1%. Nervous fibers are mostly concentrated in the middle layer. The superficial layer of the thoracolumbar fascia is also formed of three thinner sub-layers, but only the superficial one is similar to the crural fascia sub-layers, the intermediate one is similar to a flat tendon, and the deep one is formed of loose connective tissue. Only the superficial sub-layer has rich innervation and a few elastic fibers. DISCUSSION: Computerized three-dimensional models provide a detailed representation of the fascial structure, for better understanding of the interactions among the different components. This is a fundamental step in understanding the mechanical behavior of the fasciae and their role in pathology.

Differences and similarities between arrhythmogenic right ventricular cardiomyopathy and athlete's heart adaptations.

BACKGROUND: Regular intensive physical activity is associated with non-pathological changes in cardiac morphology. Differential diagnosis with arrhythmogenic right ventricular cardiomyopathy (ARVC) constitutes a frequent problem, especially in athletes showing ventricular arrhythmias with left bundle branch block morphology. AIM OF THE STUDY: To assess the different clinical and non-invasive instrumental features of the subjects affected by ARVC and by athletes. METHODS: Three groups of subjects (40 ARVC patients, 40 athletes and 40 controls, mean age 27 (9) years) were examined with family and personal history, physical examination, 12-lead ECG, 24-h ECG, signal-averaged ECG and 2-D and Doppler echocardiography. RESULTS: 12-Lead ECG was abnormal in 62% of ARVC patients versus 7.5% of athletes and 2.5% of controls (p<0.0001). Ventricular arrhythmias and late potentials were present in 70% and 55% of ARVC subjects, respectively (vs 5% of athletes and 7.5% of controls, p<0.0001). Left ventricular parietal wall thickness and left ventricular end-diastolic diameters were significantly higher in athletes. Both athletes and ARVC patients presented a right ventricular (RV) enlargement compared with controls. Moreover, RV outflow tract, measured on parasternal long axis and at the level of aortic root, was significantly larger in ARVC patients (33.6 (4.7) mm vs 29.1 (3.4) mm and 35.6 (6.8) mm vs 30.1 (2.9) mm; p<0.0001), and RV fractional shortening and ejection fraction were significantly lower in ARVC patients compared with athletes (40 (7.9)% vs 44 (10)%; p=0.05 and 52.9 (8)% vs 59.9 (4.5)%; p<0.0001). A thickened moderator band was found to be present in similar percentage in ARVC patients and athletes. CONCLUSIONS: An accurate clinical and instrumental non-invasive evaluation including echocardiography as imaging technique allows to distinguish RV alterations typical of ARVC from those detected in athletes as a consequence of intensive physical activity.

Thyroid hormone and thyrotropin regulate intracellular free calcium concentrations in human polymorphonuclear leukocytes: in vivo and in vitro studies.

Intracellular free calcium concentrations (Ca++i) were studied in polymorphonuclear leukocytes (PMNs) from 13 athyreotic patients who had been previously treated by total thyroidectomy and radioiodine therapy for differentiated thyroid carcinoma, and from age- and sex-matched euthyroid healthy controls. Patients were studied twice, when hypothyroid (visit 1) and after restoration of euthyroidism by L-T4 TSH-suppressive therapy (visit 2). PMNs from patients at visit 1 had significantly lower resting (Ca++)i levels compared to both visit 2 and controls. Values at visit 2 did not differ from those of the controls. Stimulus-induced (Ca++)i rise was also significantly blunted at visit 1 and normalized at visit 2, possibly through a differential contribution of distinct intracellular Ca++ stores, as suggested by the response pattern to the chemotactic agent, N-formyl-Met-Leu-Phe (fMLP), to the selective SERCA pump inhibitor, thapsigargine, and to the mitochondrial uncoupler, carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP). In vitro treatment of PMNs from healthy subjects with high TSH concentrations impaired intracellular Ca++ store function. Both resting (Ca++)i levels and fMLP-induced (Ca++)i rise increased in the presence either of low-concentration TSH or of T4, but effects of TSH and T4 were not additive. T3, rT3, and TRIAC had no effect. In conclusion, this study provides evidence for a direct relationship between thyroid status and (Ca++)i homeostasis in human PMNs, mainly related to direct actions of TSH and T4 on these cells.

Calcium-channel blockers and gastrointestinal motility: basic and clinical aspects.

Several calcium-channel blockers currently in use for the treatment of cardiovascular disorders have recently been tested for their effects on gastrointestinal motility. The rationale for this approach centers on the concept that calcium-channel blockers are at least as potent in inhibiting intestinal smooth muscle as in relaxing vascular smooth muscle. This review will give an outline of the most recent findings on the role of calcium and calcium channels in smooth muscle and neuronal function in the digestive system. It will also consider the mechanisms by which calcium-channel blockers may affect gastrointestinal motility and assess potential clinical applications in gastroenterology. The main goal for researchers in this field will be the development of gut-selective agents, with no cardiovascular side effects.

Adrenergic mechanisms in the control of gastrointestinal motility: from basic science to clinical applications.

Over the years, a vast literature has accumulated on the adrenergic mechanisms controlling gut motility, blood flow, and mucosal transport. The present review is intended as a survey of key information on the relevance of adrenergic mechanisms modulating gut motility and will provide an outline of our knowledge on the distribution and functional role of adrenoceptor subtypes mediating motor responses. alpha1-Adrenoceptors are located postsynaptically on smooth muscle cells and, to a lesser extent, on intrinsic neurons; alpha2-adrenoceptors may be present both pre- and postsynaptically, with presynaptic auto- and hetero-receptors playing an important role in the modulation of neurotransmitter release; beta-adrenoceptors are found mainly on smooth muscle cells. From a clinical standpoint, adrenoceptor agonists/antagonists have been investigated as potential motility inhibiting (antidiarrheal/antispasmodic) or prokinetic agents, although at present their field of application is limited to select patient groups.

Diazepam-binding inhibitor-derived peptides induce intracellular calcium changes and modulate human neutrophil function.

We studied the effects of two diazepam-binding inhibitor (DBI)-derived peptides, triakontatetraneuropeptide (DBI 17-50, TTN) and eiksoneuropeptide (DBI 51-70, ENP), on cytosolic free Ca2+ concentrations ([Ca2+]i), chemotaxis, superoxide anion (O2-) generation, and phagocytosis in human neutrophils. Both TTN and ENP induced a rapid and transient rise of [Ca2+]i. The effect of TTN depended on the presence of extracellular Ca2+, whereas the effect of ENP also persisted after extracellular Ca2+ chelation. TTN induced neutrophil chemotaxis, stimulated O2- generation, and enhanced phagocytosis. ENP did not affect cell migration and oxidative metabolism but enhanced phagocytosis. Both peptides modulated N-formyl-methionyl-leucyl-phenylalanine- and phorbol myristate acetate-induced O2- generation. Because neutrophils express benzodiazepine receptors of the peripheral type (pBRs) and DBI-derived peptides may interact with such receptors, we investigated the possible role of pBRs in TTN- or ENP-induced effects. The synthetic pBR ligand RO 5-4864 increased [Ca2+]i through extracellular Ca2+ influx and this effect was prevented by the pBR antagonist PK-11195. RO 5-4864, however, was ineffective on neutrophil migration and O2- generation and only slightly affected phagocytosis. Moreover, PK-11195 delayed the [Ca2+]i rise induced by TTN but did not significantly affect its extent, and had no effect on the [Ca2+]i rise induced by ENP. We conclude that DBI-derived peptides induce [Ca2+]i changes and modulate neutrophil function mainly through pBR-independent pathways. In view of the wide cell and tissue distribution of DBI in the brain and in peripheral organs, modulation of neutrophil function by DBI-derived peptides may be relevant for both the neuroimmune network and the development and regulation of the inflammatory processes.

Endogenous catecholamine synthesis, metabolism storage, and uptake in human peripheral blood mononuclear cells.

Evidence has been obtained that peripheral blood mononuclear cells contain dopamine, norepinephrine, epinephrine, and their metabolites. Pharmacologic inhibition of tyrosine hydroxylase or monoamine oxidase profoundly affected intracellular catecholamines (CTs) and their metabolites, indicating that these cells are able to synthesize and breakdown CTs. The sensitivity of intracellular CTs to reserpine and the presence of CTs in the extracellular medium suggest that CTs are stored and released. Moreover, the increase of extracellular CTs in the presence of monoamine uptake blockers point to the presence of functional uptake mechanisms. Altogether, these results indicate the existence of a CT lifecycle in human mononuclear cells and warrant further studies to investigate the role of adrenergic autoregulatory mechanisms in modulation of the immune response and in the pathogenesis of diseases involving the immune system.

Neural and endogenous catecholamines in the bone marrow. Circadian association of norepinephrine with hematopoiesis?

Members of our research team have recently reported that adrenergic agents may affect hematopoiesis via alpha1-adrenoceptors present on bone marrow B cell precursors. In this paper we demonstrate that murine bone marrow contains a substantial amount of catecholamines. Norepinephrine (NE) and dopamine (DA) exhibited a daily rhythmicity, with peak values observed during the night. The rhythm was disrupted by chemical sympathectomy, whereas epinephrine (E) showed no rhythmicity or sensitivity to 6-hydroxydopamine. High and low values of NE and DA were associated with high and low values of their metabolites, which indicated a rhythmic catecholamine release. NE, but not DA or E, was positively associated with the proportion of cells in the G2/M and S phases of the cell cycle. Moreover, NE and DA were found in both short-term and long-term bone marrow cultures as well as in human or murine B lymphoid cell lines. These findings indicate that endogenous catecholamines in the bone marrow have both neural and cellular origins. The neural input shows a daily rhythm and may be implicated in the regulation of hematopoiesis.

Interaction between phenytoin and valproic acid: plasma protein binding and metabolic effects.

The effect of sodium valproate (400 mg three times daily) on the disposition kinetics of intravenous phenytoin (250 mg) was investigated in seven normal subjects. After valproate, the free (unbound) fraction of phenytoin in serum rose from 9.6 +/- 0.9% (SD) to 15.6 +/- 1.4% on average (p < 0.001). The effect was associated with an increase in systemic clearance and apparent volume of distribution of total drug. There was a strong positive correlation between percent increment in each of these parameters and percent increment in unbound drug in serum. Free phenytoin concentration in serum and phenytoin concentration in saliva increased during valproate administration. As a result, both the clearance and the apparent volume of distribution of free drug were reduced. There was an increase in the renal excretion of unchanged phenytoin during valproate administration, but the effect was too small to have an appreciable influence on the overall clearance of the drug. There were no consistent changes in the excretion of the major metabolite 5, p-hydroxyphenyl, 5-phenyl, hydantoin (pHPPH), in the urine. These results suggest that valproic acid may have two separate and opposing effects on phenytoin disposition: (1) displacing phenytoin from plasma protein binding sites, thereby enhancing the systemic clearance of total drug, and (2) inhibiting phenytoin metabolism, thereby increasing the concentration of free drug in the serum.

Early signs of cardiac involvement in hypertension.

BACKGROUND: Whether abnormalities of diastolic function are the earliest cardiac change in hypertension is still a matter for dispute. The aim of this study was to assess whether left ventricular diastolic dysfunction is an early sign of cardiac involvement in hypertension. METHODS: In 578 young patients with stage I hypertension from the Hypertension and Ambulatory Recording Venetia Study (HARVEST) and 101 normotensive control patients echocardiographic Doppler examination and ambulatory blood pressure monitoring were performed. RESULTS: Left ventricular mass, wall thickness, and relative wall thickness, adjusted for confounders, were greater in the hypertensive than in the normotensive patients (all P <.0001). After adjustment for confounders, the A-wave peak velocity was higher in the hypertensive patients (51.5 +/- 11.5 vs 43.4 +/- 8 cm/s, P <.001) as were A-wave velocity time integral (5.6 +/- 1.7 vs 4.6 +/- 1.3 cm, P =.01), total area (16.9 +/- 4.4 vs 15.6 +/- 3.1 cm, P =.04), and E-wave peak velocity (69.9 +/- 15.2 vs 67.5 +/- 13.3 cm/s, P =.03). All indexes of diastolic function were similar in the hypertensive subjects subdivided according to whether they had "white-coat" or sustained hypertension. Among the hypertensive subjects, age and heart rate were the strongest predictors of diastolic indexes, whereas ambulatory blood pressure explained only a marginal part of the E/A ratio, A-wave peak velocity, and the first one third total area ratio (P =.04, P =.02, and P =.05, respectively). Left ventricular mass and wall thickness were not associated with any Doppler index. When a clustering of diastolic indexes (E/A wave ratio, deceleration time, first one third of diastole, and peak E-wave-velocity) was used to identify subjects with diastolic dysfunction, no significant differences in either clinic or ambulatory blood pressure were observed between the group with diastolic dysfunction and the group with normal function. CONCLUSIONS: We conclude that the earliest signs of cardiac involvement in hypertension are left ventricular structural abnormalities. Left ventricular diastolic function is only marginally affected, even when multiple parameters of left ventricular filling are taken into account.

P2 receptors in the murine gastrointestinal tract.

The actions of adenosine, adenosine 5'-triphosphate (ATP), 2-methylthio adenosine diphosphate ADP (2-MeSADP), 2-methylthio ATP (2-MeSATP), alpha,beta-methylene ATP (alpha,beta-meATP) and uridine triphosphate (UTP) on isolated segments of mouse stomach (fundus), duodenum, ileum and colon were investigated. The localization of P2Y(1), P2Y(2), P2Y(4), P2X(1) and P2X(2) receptors and neuronal nitric oxide synthase (NOS) were examined immunohistochemically, and P2Y(1) mRNA was examined with in situ hybridization. The order of potency for relaxation of longitudinal muscle of all regions was: 2-MeSADP>/=2-MeSATP>alpha,beta-meATP>ATP=UTP=adenosine. This is suggestive of P2Y(1)-mediated relaxation and perhaps a further P2Y receptor subtype sensitive to alpha,beta-meATP. As ATP and UTP are equipotent, the presence of a P2Y(2) receptor is indicated. ATP responses were inhibited by the P2Y(1)-selective antagonist MRS 2179, and suramin. P2Y(1) receptors were visualized immunohistochemically in the smooth muscle of the ileum and in a subpopulation for myenteric neurones, which also stained for NOS. P2Y(1) mRNA was localized in neurones in both myenteric and submucosal ganglia in the ileum. Taken together, these results suggest that ATP was acting on non-adrenergic, non-cholinergic inhibitory neurons, which release both nitric oxide (NO) and ATP. Reduced relaxations to 2-MeSADP by tetrodotoxin and N(omega)-nitro-L-arginine methyl ester, are consistent with this possibility. Adenosine acts via P1 receptors to relax smooth muscle of the mouse gut. Segments of mouse colon (in contrast to the stomach and small intestine) were contracted by nucleotides with the potency order: 2-MeSATP>alpha,betameATP>ATP; the contractions showed no desensitization and were antagonized by suramin and PPADS, consistent with responses mediated by P2X(2) receptors. Immunoreactivity to P2X(2) receptors was demonstrated on both longitudinal and circular muscle of the colon, but not in the other regions of the gut, except for a small subpopulation of myenteric neurones. In summary, neuronal P2Y(1) receptors appear to mediate relaxation, largely through NO in all regions of the mouse gut, and to a lesser extent by P2Y(1), P2Y(2) and a novel P2Y receptor subtype responsive to alpha,beta-meATP in smooth muscle, while P2X(2) receptors mediate contraction of colonic smooth muscle.

An improved method for studying the peristaltic reflex in the isolated colon.

1. A method is described for studying the peristaltic reflex in the guinea-pig or cat isolated colon, using a graded localized intraluminal stimulus consisting of a solid bolus.2. The method gives an easy evaluation of propulsive activity and makes it possible to record simultaneously the segmental activity of the circular muscle in relation to the site of stimulation and the contractions and relaxations of the longitudinal muscle coat.3. The velocity of propulsion, which is a reliable measure of propulsive activity, is dependent on the degree of distension and is easily affected by physical agents and nervous stimulation. A solid bolus is propelled only when there is simultaneous ascending contraction and descending inhibition of the circular musculature.4. Since the peristaltic reflex could not be elicited from areas from which the mucosal and submucosal layers had been removed, these layers are essential for the triggering of the peristaltic reflex and for the propulsion of solid contents in the colon.

A pharmacological analysis of the peristaltic reflex in the isolated colon of the guinea-pig or cat.

1. The peristaltic reflex in the colon was elicited by a localized intraluminal stimulus. The contractile response of the longitudinal coat, which consists of two phases, begins before the start of propulsion. Although the contractions of the longitudinal and circular musculature are usually associated, they may be independent of each other. In particular, the longitudinal contraction does not seem to be necessary for propulsion.2. Both the longitudinal reflex contraction and the segmental responses of the circular muscle to distension, namely a contraction above and a relaxation below the bolus, are abolished by tetrodotoxin and ganglion blocking agents.3. In the guinea-pig, longitudinal and circular reflex contractions are usually resistant to antimuscarine, antihistamine and antitryptamine drugs but in the cat they are abolished by antimuscarine drugs. In both species, however, atropine and hyoscine can impair propulsion by blocking selectively the descending inhibition. In the cat, it is possible to find doses which abolish the descending inhibition without affecting the contractile responses of the longitudinal and circular muscle.4. Sympathetic denervation and pretreatment with reserpine do not affect the propulsive activity. The maintenance of the descending inhibition in denervated organs suggests that the inhibitory neurones to the circular muscle are not adrenergic.5. On the basis of the effects of drugs, the possible nervous mechanism subserving the polarity of propulsion has been examined. Such a mechanism seems to require an inhibitory pathway involving muscarinic receptors at some point.6. Pelvic nerve stimulation facilitates propulsive activity. The effect of transmural stimulation is different at low and at high frequencies of stimulation. The inhibitory effect of sympathetic stimulation on the reflex responses seems to be due mainly to an action on intrinsic nervous structures.

A facilitatory effect of bicuculline on the enteric neurones in the guinea-pig isolated colon.

Changes in the efficiency of the peristaltic reflex, acetylcholine (ACh) output and motor responses to transmural and periarterial nerve stimulation produced by bicuculline and gamma-aminobutyric acid (GABA) receptor desensitization were investigated in the guinea-pig isolated colon. Bicuculline, at concentrations unable to affect spontaneous colonic motility and lacking anticholinesterase activity, produced a dose-dependent increase of both the efficiency of the peristaltic reflex and the stimulated ACh output. Such effects could not be observed in GABA-desensitized preparations. A frequency-dependent potentiation of the cholinergic excitatory and non-adrenergic non-cholinergic (NANC) inhibitory responses to transmural stimulation was also observed in the presence of bicuculline. Conversely bicuculline exhibited an inhibitory effect on the relaxation induced by periarterial nerve stimulation. Acute GABA-desensitization was unable to affect the contractile responses to transmural stimulation, the ACh output and the efficiency of the peristaltic reflex. On the contrary, desensitization was able to mimic the effects of bicuculline on the inhibitory responses to both transmural and periarterial nerve stimulation. Our results are consistent with a significant role played by an intrinsic GABAergic pathway in the modulation of both cholinergic excitatory and NANC inhibitory neurones. The hypothesis is advanced that a feed-back modulation carried out through bicuculline-sensitive GABAergic synapses could operate during the propagation of peristaltic motor activity.

Purine receptors in the guinea-pig internal anal sphincter.

1 In the isolated internal anal sphincter of the guinea-pig, adenosine 5'-triphosphate (ATP) and adenosine induced a concentration-dependent and tetrodotoxin-insensitive relaxation. 2 Pretreatment with theophylline (25-50 microM) had no significant effect on the concentration-response curves obtained with either purine compound. 3 Reactive blue 2 (25-100 microM) shifted the curve to ATP to the right in a dose-dependent fashion leaving that to adenosine unaltered. The antagonism appeared to be non-competitive. 4 Neither reactive blue 2 nor purine receptor occupation by ATP or adenosine altered the electrically-induced non-adrenergic, non-cholinergic inhibitory response. 5 The actions of ATP and adenosine in the guinea-pig internal anal sphincter appear to be mediated by separate receptors. These receptors are not involved in the nerve-mediated relaxation.

Effects of desensitization to adenosine 5'-triphosphate and adenosine on non-adrenergic inhibitory responses in the circular muscle of rabbit colon.

An approximate eight fold desensitization of the circular coat of the distal rabbit colon to adenosine 5'-triphosphate (ATP) and adenosine could be achieved by repeatedly exposing the organ to relatively low concentrations (10-100 microM) of these compounds. The desensitization was specific and reversible after prolonged washing. It could be overcome by increasing the concentrations of the purine agonists. Dipyridamole potentiated the non-adrenergic inhibition in response to transmural stimulation but failed to influence the caudad relaxation evoked by radial distension. Desensitization to ATP and adenosine (and to ATP + adenosine simultaneously) did not affect the non-adrenergic inhibition in response to radial distension or transmural stimulation. These results suggest that neither ATP nor adenosine are the final transmitters mediating the non-adrenergic inhibitory responses in the distal colon of the rabbit.

Selectivity of Ca2+ channel blockers in inhibiting muscular and nerve activities in isolated colon.

1. Potency and efficacy of nifedipine, verapamil and diltiazem and of Bay K 8644 in modifying propulsion and nerve or smooth muscle activities have been compared in the guinea-pig isolated distal colon. Both the neuronal and muscular effects of Ca2+ channel blockers seem to develop at concentrations that are devoid of any significant effect apart from that on Ca2+ channels. 2. Nifedipine, verapamil and diltiazem were all able to impair propulsion, resting and stimulated acetylcholine (ACh) release and smooth muscle contractility in a concentration-dependent way. However, some degree of selectivity for neuronal and muscular effects could be observed. Nifedipine was more than 500 fold more potent than verapamil in relaxing musculature but less than twice as potent in reducing ACh release. On the other hand, verapamil was the most efficacious Ca2+ channel blocker tested in inhibiting ACh release, its effects being inversely correlated to the external Ca2+ concentration, and completely abolished by Bay K 8644. 3. By comparing the potencies exhibited by each drug against peristaltic reflex, smooth muscle contractility and ACh release, verapamil proved to be almost as potent in slowing the peristaltic reflex as in reducing ACh release, while nifedipine was about 100 fold more potent against the peristaltic reflex than against ACh release, but nearly equal against the peristaltic reflex and smooth muscle tone. Therefore, interference with cholinergic neurotransmission is likely to play a major role in the antipropulsive effect of verapamil, while peristaltic reflex impairment by nifedipine is likely to be dependent on inhibition of smooth muscle. 4. A facilitatory effect of Bay K 8644 on both the efficiency of the peristaltic reflex and the nonadrenergic, non-cholinergic (NANC) nerve-mediated relaxation could be observed at concentrations at least 10 fold lower than those required to affect ACh release or smooth muscle. 5. It is concluded that the effects of Ca2+ channel blockers on neurotransmitter release may be relevant to their effects on the gastrointestinal motor function.

Inhibitory effects of SR 58611A on canine colonic motility: evidence for a role of beta 3-adrenoceptors.

1. In order to clarify whether atypical or beta 3-adrenoceptors can modulate canine colonic motility in vivo, we studied the effects of SR 58611A (a selective agonist for atypical beta-adrenoceptors) alone and after pretreatment with beta-adrenoceptor antagonists on colonic motility in the conscious dog. The gastrocolonic response (postprandial increase in motility) was monitored by means of electrodes and strain-gauge force transducers chronically implanted along the distal colon. In some experiments, heart rate was also measured. The possible role of beta 3-adrenoceptors in mediating the effects of SR 58611A was also tested in vitro in circular muscle strips taken from the canine distal colon. 2. Intravenous infusion of SR 58611A, ritodrine or isoprenaline at doses inducing the same degree of tachycardia inhibited the gastrocolonic response to a different extent, with SR 58611A and ritodrine being more effective than isoprenaline. 3. In a dose-response study, SR 58611A was more potent in inhibiting colonic motility than in inducing tachycardia: the ED35 values for inhibition of colonic motility and induction of tachycardia were 23 and 156 micrograms kg-1, i.v., respectively. 4. The inhibitory effect of SR 58611A 100 micrograms kg-1, i.v., on the gastrocolonic response was reversed by alprenolol (non-selective beta-adrenoceptor antagonist), but resistant to CGP 20712A (beta 1-adrenoceptor antagonist) or ICI 118551 (beta 2-adrenoceptor antagonist). 5. In vitro, SR 58611A concentration-dependently relaxed circular muscle strips, an effect that was competitively antagonized by alprenolol with a pA2 value of 7.1, but resistant to CGP 20712A (100 nM), ICI 118551 (100 nM) or tetrodotoxin (1 microM). 6. The present study provides strong functional evidence for a role of atypical or beta 3-adrenoceptors in the modulation of canine colonic motility both in vivo and in vitro by an inhibitory effect most likely at the smooth muscle level.

An in vitro study of the relationship between GABA receptor function and propulsive motility in the distal colon of the rabbit.

1. The effects of gamma-aminobutyric acid (GABA), 3-aminopropane sulphonic acid (3-APS) and baclofen on spontaneous, electrically-induced and propulsive motility were investigated in rabbit distal colon. 2. In unstimulated longitudinal (LMPs) and circular muscle strip preparations (CMPs) 3-APS (10-200 microM) and GABA caused a clear-cut relaxation susceptible to desensitization. Baclofen (10-200 microM) caused relaxation in a minority (30%) of preparations. The 3-APS response was sensitive to tetrodotoxin (TTX; 1 microM), SR 95531 (a novel competitive GABAA-receptor antagonist) (10 microM), picrotoxinin (30 microM), and insensitive to hyoscine (1 microM) and to a combination of prazosin (1 microM) and propranolol (1 microM). The baclofen response was antagonized by 5-aminovaleric acid (DAVA, 500 microM), TTX and hyoscine and resistant to GABAA-receptor and adrenoceptor blockade. GABAA-receptors were therefore associated with non-adrenergic non-cholinergic (NANC) inhibitory nerve activation while GABAB-receptors were involved in depression of cholinergic tone of smooth muscle. GABA (10-200 microM) elicited both above mentioned effects. 3. In LMPs, baclofen (10-200 microM) dose-dependently inhibited submaximal responses to both cholinergic and NANC inhibitory nerve stimulation. This effect was resistant to SR 95531 and picrotoxinin and prevented by DAVA and baclofen desensitization. GABA (10-200 microM) mimicked the action of baclofen. GABA inhibitory effects persisted in the presence of GABAA-receptor blockade. 4. In segments of distal colon, GABA and baclofen (1-200 microM), but not 3-APS (1-200 microM), dose-dependently decreased the velocity of propulsion of an intraluminally-distended balloon. This effect was antagonized by DAVA and GABA or baclofen desensitization and resistant to SR 95531 and picrotoxinin. These antagonists per se had no effect on propulsion. In preparations in which propulsion was slowed by hyoscine (1 microM), baclofen caused no consistent further depression of propulsive activity. 5. Our results show that GABAA- and GABAB-receptors are present in rabbit colon. GABAA-receptor stimulation activates NANC inhibitory nerves without apparently affecting propulsion. GABAB-receptors are associated with a reduction of neural (mainly cholinergic) activity subserving muscular tone and peristalsis and appear to be located on both cholinergic and NANC inhibitory nerves. However, the persisting propulsive activity during suppression of GABAA- and GABAB-receptor function suggests that GABA in enteric neurones is not crucial for the neural circuitry subserving colonic peristalsis in this species.

Reproducibility of heart rate measured in the clinic and with 24-hour intermittent recorders.

This study was undertaken to assess the reproducibility of office versus ambulatory heart rates in 839 hypertensive subjects participating in the Hypertension and Ambulatory Recording Venetia Study (HARVEST). A 24-hour heart rate was recorded twice; this procedure was repeated three months later. Reproducibility was better for ambulatory than for office measurement, and was greater for 24-hour than for daytime heart rate, and lowest for night-time heart rate. Reproducibility of office heart rate was impaired above 85 bpm, and was poorer in subjects with more severe office hypertension. A small but significant decrease in average daytime (-1 bpm, P < 0.0001) and virtually no change in night-time heart rate (-0.3 bpm, NS) were observed at repeat recording. Heart rate reproducibility indices were related to the extent of the heart rate and blood pressure white-coat effect, but did not vary according to age, gender, body mass index, day-night blood pressure difference, or alcohol or tobacco use. Results indicate that heart rate recorded over the 24 hours has a better reproducibility than office heart rate, and could thus be a better prognostic indicator than traditional measurement of resting heart rate in the hospital setting.