RESUMO
Nucleic acid-derived indices such as RNA/DNA ratios have been successfully applied as ecophysiological indicators to assess growth, nutritional condition and health status in marine organisms given that they provide a measure of tissue protein reserves, which is known to vary depending on changes in the environment. Yet, the use of these biochemical indices on highly mobile large predators is scarce. In this study, we tested the applicability of using nucleic acids to provide insights on the ecophysiological traits of two marine mammal species (common bottlenose dolphins and short-finned pilot whales) and explored potential related factors (species, sex, season, and residency pattern), using skin tissue (obtained from biopsy darts) of apparently healthy and adult free-ranging animals. Significantly higher RNA/DNA ratios were obtained for bottlenose dolphins (p < 0.001), and for visitor pilot whales when compared with resident pilot whales (p = 0.001). No significant changes were found between the sexes. Based on the percentile approach, the samples contain individuals in a general good condition (as the 10th percentile is not closer to the mean than the 75th percentile), suggesting that the studied region of Macaronesia may be considered an adequate habitat. The combination of this effective tool with genetic sexing and photographic-identification provided an overall picture of ecosystem health, and although with some limitations and still being a first approach, it has the applicability to be used in other top predators and ecosystems.
Assuntos
Organismos Aquáticos/genética , Organismos Aquáticos/fisiologia , Golfinho Nariz-de-Garrafa/genética , Golfinho Nariz-de-Garrafa/fisiologia , Ecossistema , Baleias Piloto/genética , Baleias Piloto/fisiologia , África do Norte , Animais , Oceano Atlântico , DNA/genética , Feminino , Cadeia Alimentar , Masculino , RNA/genética , Estações do AnoRESUMO
Whole-cell patch clamp recordings were made from neurons of the rat subpostremal region of the nucleus tractus solitarius (NTS) in transverse brainstem slices. Neurotensin (NT) enhanced the firing rate of action potentials from 0.8 +/- 0.4 Hz in control to 1.9 +/- 1.3 Hz (n = 9) and increased their decay time. The peak amplitude of the after-hyperpolarization was decreased by 34+/-5% (n = 9). These effects were associated with a depolarization of 4 +/- 1 mV (n = 10) in the resting membrane potential and an increase in the input resistance (from 768 +/- 220 MOmega to 986+/-220 MOmega; n = 5) and were compensated by manually hyperpolarizing the cell to control values. In voltage clamp experiments NT decreased an outward current (from 488 +/- 161 to 340 +/- 96 pA at +40 mV; n = 5) which reversed near the potassium equilibrium potential. In addition, NT increased the frequency of both excitatory and inhibitory spontaneous synaptic currents, an effect blocked by tetrodotoxin, and did not change the evoked excitatory or inhibitory postsynaptic currents. The selective NTR1 receptor antagonist SR48692 reversibly blocked the effects of NT on both action potentials and spontaneous synaptic currents. Our results suggest that NTR1 receptors can modulate post-synaptic responses in neurons of the subpostremal NTS by increasing cell excitability as a result of blockade of a potassium conductance.
Assuntos
Neurotensina/metabolismo , Terminações Pré-Sinápticas/metabolismo , Núcleo Solitário/metabolismo , Transmissão Sináptica/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Feminino , Masculino , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Neurotensina/farmacologia , Técnicas de Cultura de Órgãos , Técnicas de Patch-Clamp , Canais de Potássio/efeitos dos fármacos , Canais de Potássio/metabolismo , Terminações Pré-Sinápticas/efeitos dos fármacos , Pirazóis/farmacologia , Quinolinas/farmacologia , Ratos , Ratos Wistar , Receptores de Neurotensina/antagonistas & inibidores , Receptores de Neurotensina/metabolismo , Núcleo Solitário/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacosRESUMO
Esophageal sensory afferent inputs terminate principally in the central subnucleus of the tractus solitarius (cNTS). Neurons of the cNTS comprise two major neurochemical subpopulations. One contains neurons that are nitric oxide synthase (NOS) immunoreactive (-IR) while the other comprises neurons that are tyrosine hydroxylase (TH)-IR. We have shown recently that TH-IR neurons are involved in esophageal-distention induced gastric relaxation. We used whole cell patch clamp techniques in rat brainstem slices combined with immunohistochemical and morphological reconstructions to characterize cNTS neurons. Postrecording reconstruction of cNTS neurons revealed two morphological neuronal subtypes; one group of cells (41 out of 131 neurons, i.e., 31%) had a multipolar soma, while the other group (87 out of 131 neurons, i.e., 66%) had a bipolar soma. Of the 43 cells in which we conducted a neurochemical examination, 15 displayed TH-IR (9 with bipolar morphology, 6 with multipolar morphology) while the remaining 28 neurons did not display TH-IR (18 with bipolar morphology, 10 with multipolar morphology). Even though the range of electrophysiological properties varied significantly, morphological or neurochemical distinctions did not reveal characteristics peculiar to the subgroups. Spontaneous excitatory postsynaptic currents (sEPSC) recorded in cNTS neurons had a frequency of 1.5 +/- 0.15 events s(-1) and an amplitude of 27 +/- 1.2 pA (Vh = -50 mV) and were abolished by pretreatment with 30 muM AP-5 and 10 muM CNQX, indicating the involvement of both NMDA and non-NMDA receptors. Some cNTS neurons also received a GABAergic input that was abolished by perfusion with 30-50 muM bicuculline. In conclusion, our data show that despite the heterogeneity of morphological and neurochemical membrane properties, the electrophysiological characteristics of cNTS neurons are not a distinguishing feature.
Assuntos
Neurônios/classificação , Neurônios/fisiologia , Núcleo Solitário/citologia , 2-Amino-5-fosfonovalerato/farmacologia , 6-Ciano-7-nitroquinoxalina-2,3-diona/farmacologia , Animais , Animais Recém-Nascidos , Biotina/análogos & derivados , Biotina/metabolismo , Contagem de Células/métodos , Tamanho Celular , Relação Dose-Resposta à Radiação , Interações Medicamentosas/fisiologia , Estimulação Elétrica/métodos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Imuno-Histoquímica/métodos , Técnicas In Vitro , Masculino , Potenciais da Membrana/fisiologia , Potenciais da Membrana/efeitos da radiação , Neurônios/efeitos dos fármacos , Técnicas de Patch-Clamp/métodos , Ratos , Ratos Sprague-Dawley , Coloração e Rotulagem/métodos , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
The nucleus tractus solitarius (NTS) plays an important role in the control of autonomic reflex functions. Glutamate, acting on N-methyl-D-aspartate (NMDA) and non-NMDA ionotropic receptors, is the major neurotransmitter in this nucleus, and the relative contribution of each receptor to signal transmission is unclear. We have examined NMDA excitatory postsynaptic currents (NMDA-EPSCs) in the subpostremal NTS using the whole cell patch clamp technique on a transverse brainstem slice preparation. The NMDA-EPSCs were evoked by stimulation of the solitary tract over a range of membrane potentials. The NMDA-EPSCs, isolated pharmacologically, presented the characteristic outward rectification and were completely blocked by 50 microM DL-2-amino-5-phosphonopentanoic acid. The I-V relationship of the NMDA response shows that current, with a mean (+/- SEM) amplitude of -41.2 +/- 5.5 pA, is present even at a holding potential of -60 mV, suggesting that the NMDA receptors are weakly blocked by extracellular Mg2+ at near resting membrane potentials. This weak block can also be inferred from the value of 0.67 +/- 0.17 for parameter delta obtained from a fit of the Woodhull equation to the I-V relationship. The maximal inward current measured on the I-V relationship was at -38.7 +/- 4.2 mV. The decay phase of the NMDA currents was fitted with one exponential function with a decay time constant of 239 +/- 51 and 418 +/- 80 ms at a holding potential of -60 and +50 mV, respectively, which became slower with depolarization (e-fold per 145 mV). The biophysical properties of the NMDA receptors observed in the present study suggest that these receptors in the NTS contain NR2C subunits and may contribute to the synaptic signal integration.
Assuntos
Neurônios/química , Receptores de N-Metil-D-Aspartato/análise , Núcleo Solitário/química , Sinapses/fisiologia , Transmissão Sináptica/fisiologia , Animais , Eletrofisiologia , Feminino , Masculino , Potenciais da Membrana/fisiologia , Neurônios/fisiologia , Técnicas de Patch-Clamp , Ratos , Ratos Wistar , Núcleo Solitário/fisiologiaRESUMO
Chronic hepatitis C virus (HCV) infection exists in a large proportion of patients undergoing renal transplantation. Nowadays it is not considered to be an absolute contraindication to transplantation; however, it is associated with an increased risk for the patient and accounts for a shorter half-life of the renal allograft. We present three transplant recipients who displayed serious hepatic dysfunction after renal transplantation due to an HCV infection. In two of these cases, the liver biopsies established the diagnosis of FCH. In the third case, the liver biopsy was compatible with the early stages of FCH. All patients were started on peg-interferon alfa 2-b and ribavirin with subsequent normalization of hepatic function and early complete viral responses.
Assuntos
Hepatite C Crônica/tratamento farmacológico , Transplante de Rim , Adulto , Antivirais/administração & dosagem , Antivirais/uso terapêutico , Biópsia , Feminino , Hepatite C Crônica/patologia , Humanos , Interferon alfa-2 , Interferon-alfa/administração & dosagem , Interferon-alfa/uso terapêutico , Fígado/patologia , Masculino , Pessoa de Meia-Idade , Proteínas Recombinantes , Ribavirina/administração & dosagem , Ribavirina/uso terapêuticoRESUMO
We have shown recently that cholecystokinin octapeptide (CCK-8s) increases glutamate release from nerve terminals onto neurons of the nucleus tractus solitarius pars centralis (cNTS). The effects of CCK on gastrointestinal-related functions have, however, been attributed almost exclusively to its paracrine action on vagal afferent fibers. Because it has been reported that systemic or perivagal capsaicin pretreatment abolishes the effects of CCK, the aim of the present work was to investigate the response of cNTS neurons to CCK-8s in vagally deafferented rats. In surgically deafferented rats, intraperitoneal administration of 1 or 3 mug/kg CCK-8s increased c-Fos expression in cNTS neurons (139 and 251% of control, respectively), suggesting that CCK-8s' effects are partially independent of vagal afferent fibers. Using whole cell patch-clamp techniques in thin brain stem slices, we observed that CCK-8s increased the frequency of spontaneous and miniature excitatory postsynaptic currents in 43% of the cNTS neurons via a presynaptic mechanism. In slices from deafferented rats, the percentage of cNTS neurons receiving glutamatergic inputs responding to CCK-8s decreased by approximately 50%, further suggesting that central terminals of vagal afferent fibers are not the sole site for the action of CCK-8s in the brain stem. Taken together, our data suggest that the sites of action of CCK-8s include the brain stem, and in cNTS, the actions of CCK-8s are not restricted to vagal central terminals but that nonvagal synapses are also involved.
Assuntos
Neurônios/efeitos dos fármacos , Sincalida/farmacologia , Núcleo Solitário/efeitos dos fármacos , Nervo Vago/cirurgia , Analgésicos não Narcóticos/farmacologia , Animais , Tronco Encefálico/citologia , Tronco Encefálico/efeitos dos fármacos , Tronco Encefálico/fisiologia , Capsaicina/farmacologia , Relação Dose-Resposta a Droga , Eletrofisiologia , Feminino , Injeções Intraperitoneais , Masculino , Neurônios/metabolismo , Técnicas de Patch-Clamp/métodos , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-Dawley , Sincalida/administração & dosagem , Núcleo Solitário/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologia , Nervo Vago/efeitos dos fármacosRESUMO
Cholecystokinin (CCK) is released from enteroendocrine cells after ingestion of nutrients and induces multiple effects along the gastrointestinal tract, including gastric relaxation and short-term satiety. We used whole cell patch-clamp and immunohistochemical techniques in rat brain stem slices to characterize the effects of CCK. In 45% of the neurons of nucleus tractus solitarius subnucleus centralis (cNTS), perfusion with the sulfated form of CCK (CCK-8s) increased the frequency of spontaneous excitatory currents (sEPSCs) in a concentration-dependent manner (1-300 nM). The threshold for the CCK-8s excitatory effect was 1 nM, the EC(50) was 20 nM, and E(max) was 100 nM. The excitatory effects of CCK-8s were still present when the slices were preincubated with tetrodotoxin or bicuculline or when the recordings were conducted with Cs(+) electrodes. Pretreatment with the CCK-A receptor antagonist, lorglumide (1 microM), antagonized the effects of CCK-8s, whereas perfusion with the CCK-B preferring agonist CCK-8 nonsulfated (CCK-ns, 1 microM) did not affect the frequency of sEPSCs. Similarly, pretreatment with the CCK-B receptor antagonist, triglumide (1 microM), did not prevent the actions of CCK-8s. Although the majority (i.e., 76%) of CCK-8s unresponsive cNTS neurons had a bipolar somata shape and were TH-IR negative, no differences were found in either the morphological or the neurochemical phenotype of cNTS neurons responsive to CCK-8s. Our results suggest that the excitatory effects of CCK-8s on terminals impinging on a subpopulation of cNTS neurons are mediated by CCK-A receptors; these responsive neurons, however, do not have morphological or neurochemical characteristics that automatically distinguish them from nonresponsive neurons.
Assuntos
Neurônios/efeitos dos fármacos , Sincalida/farmacologia , Núcleo Solitário/citologia , Transmissão Sináptica/efeitos dos fármacos , Anestésicos Locais/farmacologia , Animais , Animais Recém-Nascidos , Bicuculina/farmacologia , Biotina/análogos & derivados , Biotina/metabolismo , Relação Dose-Resposta a Droga , Interações Medicamentosas , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Antagonistas GABAérgicos/farmacologia , Ácido Glutâmico/metabolismo , Antagonistas de Hormônios/farmacologia , Imageamento Tridimensional/métodos , Imuno-Histoquímica/métodos , Técnicas In Vitro , Masculino , Inibição Neural/efeitos dos fármacos , Neurônios/metabolismo , Técnicas de Patch-Clamp/métodos , Peptídeos/farmacologia , Proglumida/análogos & derivados , Proglumida/farmacologia , Ratos , Ratos Sprague-Dawley , Núcleo Solitário/fisiologia , Transmissão Sináptica/fisiologia , Tetrodotoxina/farmacologia , Tirosina 3-Mono-Oxigenase/metabolismoRESUMO
The nucleus tractus solitarius (NTS) plays an important role in the control of autonomic reflex functions. Glutamate, acting on N-methyl-D-aspartate (NMDA) and non-NMDA ionotropic receptors, is the major neurotransmitter in this nucleus, and the relative contribution of each receptor to signal transmission is unclear. We have examined NMDA excitatory postsynaptic currents (NMDA-EPSCs) in the subpostremal NTS using the whole cell patch clamp technique on a transverse brainstem slice preparation. The NMDA-EPSCs were evoked by stimulation of the solitary tract over a range of membrane potentials. The NMDA-EPSCs, isolated pharmacologically, presented the characteristic outward rectification and were completely blocked by 50 æM DL-2-amino-5-phosphonopentanoic acid. The I-V relationship of the NMDA response shows that current, with a mean (± SEM) amplitude of -41.2 ± 5.5 pA, is present even at a holding potential of -60 mV, suggesting that the NMDA receptors are weakly blocked by extracellular Mg2+ at near resting membrane potentials. This weak block can also be inferred from the value of 0.67 ± 0.17 for parameter delta obtained from a fit of the Woodhull equation to the I-V relationship. The maximal inward current measured on the I-V relationship was at -38.7 ± 4.2 mV. The decay phase of the NMDA currents was fitted with one exponential function with a decay time constant of 239 ± 51 and 418 ± 80 ms at a holding potential of -60 and +50 mV, respectively, which became slower with depolarization (e-fold per 145 mV). The biophysical properties of the NMDA receptors observed in the present study suggest that these receptors in the NTS contain NR2C subunits and may contribute to the synaptic signal integration.