RESUMO
Pressor responses to l-glutamate into the rostroventrolateral medulla (RVLM) are reduced by lesions of the anteroventral third ventricle (AV3V) region, a main site related to central angiotensinergic pressor mechanisms. Therefore, similar to AV3V lesions, in the present study we investigated if the blockade of central angiotensinergic mechanisms with losartan or ZD 7155 might affect pressor responses to l-glutamate into the RVLM. Male Holtzman rats (280-320g, n=4-8/group) with cannulas implanted into the RVLM and lateral ventricle (LV) were used. Injections of l-glutamate (5nmol/100nl) or angiotensin II (200ng/100nl) into the RVLM increased MAP (54+/-5 and 26+/-3mm Hg, respectively). Losartan (100 microg/1 microl) or ZD 7155 (50 microg/1 microl) injected into the LV reduced the pressor responses to l-glutamate into the RVLM (22+/-5 and 26+/-7mm Hg, respectively), without changing the pressor responses to angiotensin II into the RVLM. Losartan (10 microg/100 nl) or ZD 7155 (5 microg/100 nl) into the RVLM reduced the pressor response to l-glutamate (5+/-3 and 33+/-4mm Hg, respectively) or angiotensin II (5+/-3 and 6+/-2mm Hg, respectively) into the RVLM. Previous injection of angiotensin II (50ng/100nl) into the RVLM increased the pressor response to l-glutamate into the RVLM (from 44+/-5 to 68+/-7mm Hg). The results suggest that angiotensinergic mechanisms directly in the RVLM and outside the RVLM (probably forebrain) are important for the pressor responses to l-glutamate into the RVLM.
Assuntos
Angiotensinas/metabolismo , Pressão Sanguínea/fisiologia , Ácido Glutâmico/metabolismo , Bulbo/metabolismo , Vasoconstrição/fisiologia , Angiotensina II/metabolismo , Angiotensina II/farmacologia , Angiotensinas/farmacologia , Animais , Antiarrítmicos/farmacologia , Vias Autônomas/anatomia & histologia , Vias Autônomas/efeitos dos fármacos , Vias Autônomas/metabolismo , Pressão Sanguínea/efeitos dos fármacos , Fenômenos Fisiológicos Cardiovasculares , Ácido Glutâmico/farmacologia , Losartan/farmacologia , Masculino , Bulbo/anatomia & histologia , Bulbo/efeitos dos fármacos , Naftiridinas/farmacologia , Ratos , Ratos Sprague-Dawley , Formação Reticular/anatomia & histologia , Formação Reticular/efeitos dos fármacos , Formação Reticular/metabolismo , Sistema Nervoso Simpático/anatomia & histologia , Sistema Nervoso Simpático/efeitos dos fármacos , Sistema Nervoso Simpático/metabolismo , Vasoconstrição/efeitos dos fármacosRESUMO
The autonomic innervation in the heart is predominantly by postganglionic, parasympathetic, and sympathetic neurons, which are organized in a plexus of ganglions into the heart. The knowledge of the density, distribution, location, morphology, and intrinsic connection of this system that constitute the heart autonomic innervation is limited and controversial. Methods that provide clear information in this field are desirable. A widely used method to study the morphology of the nerve cells in the central nervous system (CNS) is used in this study to characterize the autonomic innervation in rat hearts. The method consisted of impregnation of the fresh whole heart of 12 adult male Wistar rats with the Golgi-Cox stain for 30 days, after which they were incubated in 30% sucrose solution for 2-3 days and then were sectioned (200 microm) with a vibratome. The tissues were mounted on gelatin-covered slides and analyzed by using the Sholl method under light microscopy adapted to a camera lucida. The results clearly show a distribution of the ganglion plexuses in the epicardium, myocardium, and endocardium, joined by an extensive network of nerve fibers in the four cardiac chambers. We also identified and characterized the morphology of an isolated cardiac nerve cell. As results similar to that in the CNS, the Golgi-Cox method is a simple, efficient, and an accessible tool to study the autonomic innervation in the rat heart and provides a good resolution of the morphology of the plexuses of the ganglions and nerve fibers.
Assuntos
Vias Autônomas/anatomia & histologia , Coração/inervação , Neurônios/citologia , Coloração e Rotulagem/métodos , Animais , Coração/anatomia & histologia , Masculino , Fotomicrografia , Ratos , Ratos WistarRESUMO
Located in the lower brainstem, the paratrigeminal nucleus (Pa5) is related to cardiorespiratory autonomic reflex functions. To characterize the structures' role in blood pressure regulation and the cardiovascular reflex responses Pa5 unit activity was evaluated during a phenylephrine-produced pressor response in non-anaesthetized rats by means of simultaneous many-unit recording. Ninety five percent of the identified Pa5 responded to baroreceptor stimulation, 77% increasing and 23% decreasing firing rates. Cross-correlation analysis of neuron electrical behavior referenced to the heart beat event revealed that 65% of the featured cardiac cycle-locked rhythmic activity. The identification of neurons that change firing rates in response to increases of arterial pressure with cardiac cycle-locked rhythmic activity, further supports for a role for the nucleus in moment to moment control of blood pressure. The largest changes in firing rate occurred in the units with low resting firing rates in response to the ascending phase of the pressor event. Thus, the group displaying both cardiac cycle-locked and other rhythmic activities within the ranges of cardiac and respiratory rates or arterial pressure low frequencies, is probably the most influential regarding homoeostatic reflex responses. The findings advance the notion that the dynamic control of blood pressure involves lower brainstem integration of cardiac and respiratory reflexes.
Assuntos
Sistema Nervoso Autônomo/fisiologia , Pressão Sanguínea/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Bulbo/fisiologia , Neurônios/fisiologia , Fenômenos Fisiológicos Respiratórios , Potenciais de Ação/fisiologia , Anestésicos/farmacologia , Animais , Sistema Nervoso Autônomo/anatomia & histologia , Vias Autônomas/anatomia & histologia , Vias Autônomas/fisiologia , Frequência Cardíaca/fisiologia , Masculino , Bulbo/anatomia & histologia , Ratos , Ratos Wistar , Reflexo/fisiologia , Núcleo Espinal do Trigêmeo/anatomia & histologiaRESUMO
The medial prefrontal cortex (MPFC) is involved in cardiovascular control. MPFC electrical stimulation has been reported to cause depressor and bradycardic responses in anesthetized rats. Although the pathway involved is yet unknown, there is evidence indicating the existence of a relay in the lateral hypothalamus (LH). The medial forebrain bundle (MFB) that courses in the lateral portion of the LH carries the vast majority of telencephalic afferent as well efferent projections, including those from the MPFC. To evaluate if the hypotensive pathway originating in the MPFC courses the MFB, we studied the effect of coronal or sagittal knife cuts through the LH and other brain areas on the cardiovascular responses to MPFC electrical stimulation. Knife cuts were performed using blades 1 to 6 mm wide. Results indicate that the neural pathway descending from the MFB decussates early in the vicinity of MPFC, crossing the midline within the corpus callosum and yielding two descending pathways that travel rostro-caudally in the lateral portion of the LH, within the MFB. The decussation was confirmed by histological analysis of brain sections processed after the injection of biotinilated dextran amine in the site of the stimulation in the MPFC. Because knife cuts through the LH ipsilateral had minimal effects on the cardiovascular responses and knife cuts performed contralateral to the stimulated MPFC had no effect on the response to MPFC stimulation, data indicate that the contralateral limb of the pathway may be only activated as an alternative pathway when the ipsilateral pathway is blocked.
Assuntos
Vias Autônomas/fisiologia , Fenômenos Fisiológicos Cardiovasculares , Diencéfalo/fisiologia , Feixe Prosencefálico Mediano/fisiologia , Córtex Pré-Frontal/fisiologia , Animais , Vias Autônomas/anatomia & histologia , Biotina/análogos & derivados , Mapeamento Encefálico , Denervação , Dextranos , Diencéfalo/anatomia & histologia , Vias Eferentes/anatomia & histologia , Vias Eferentes/fisiologia , Estimulação Elétrica , Lateralidade Funcional/fisiologia , Região Hipotalâmica Lateral/anatomia & histologia , Região Hipotalâmica Lateral/fisiologia , Masculino , Feixe Prosencefálico Mediano/anatomia & histologia , Córtex Pré-Frontal/anatomia & histologia , Ratos , Ratos Wistar , Coloração e RotulagemRESUMO
In the present study, we report the effect of insular cortex (IC) ablation caused by bilateral microinjection of the non-selective synaptic blocker CoCl(2) on cardiac baroreflex response in unanesthetized rats as well as the involvement of local glutamatergic neurotransmission. Unilateral (left or right) microinjection of CoCl(2) (1 nmol/ 100 nL) did not affect the bradycardiac response to blood pressure increase evoked by intravenous infusion of phenylephrine nor the tachycardiac response to blood pressure decrease caused by intravenous infusion of sodium nitroprusside, 10 min after CoCl(2). Bilateral microinjection of CoCl(2) into IC decreased the magnitude of reflex bradycardia without affecting tachycardiac responses. Baroreflex activity returned to control values 60 min after CoCl(2) microinjection, confirming its reversible effect. Further we studied the possible involvement of IC-glutamatergic neurotransmission in baroreflex modulation. We observed that bilateral microinjection of the selective NMDA receptor antagonist LY235959 (4 nmol/100 nL) into the IC decreased the magnitude of reflex bradycardia without affecting tachycardiac responses. IC treatment with the selective non-NMDA antagonist NBQX (4 nmol/100 nL) did not affect baroreflex activity. The results suggest that synapses within the IC have a tonic excitatory influence on the baroreflex parasympathetic component. Moreover, the present data suggest that local NMDA-receptors are involved in the IC-mediated tonic excitatory influence on baroreflex parasympathetic activity.
Assuntos
Vias Autônomas/metabolismo , Barorreflexo/fisiologia , Córtex Cerebral/metabolismo , Ácido Glutâmico/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Anestésicos/farmacologia , Animais , Anti-Hipertensivos/farmacologia , Vias Autônomas/anatomia & histologia , Vias Autônomas/efeitos dos fármacos , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Bradicardia/induzido quimicamente , Córtex Cerebral/anatomia & histologia , Córtex Cerebral/efeitos dos fármacos , Cobalto/farmacologia , Vias Eferentes/anatomia & histologia , Vias Eferentes/efeitos dos fármacos , Vias Eferentes/metabolismo , Antagonistas de Aminoácidos Excitatórios/farmacologia , Frequência Cardíaca/efeitos dos fármacos , Frequência Cardíaca/fisiologia , Isoquinolinas/farmacologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Nitroprussiato/farmacologia , Quinoxalinas/farmacologia , Ratos , Ratos Wistar , Receptores de N-Metil-D-Aspartato/agonistas , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologiaRESUMO
To analyze the differential recruitment of the raphe nuclei during different phases of feeding behavior, rats were subjected to a food restriction schedule (food for 2 h/day, during 15 days). The animals were submitted to different feeding conditions, constituting the experimental groups: search for food (MFS), food ingestion (MFI), satiety (MFSa) and food restriction control (MFC). A baseline condition (BC) group was included as further control. The MFI and MFC groups, which presented greater autonomic and somatic activation, had more FOS-immunoreactive (FOS-IR) neurons. The MFI group presented more labeled cells in the linear (LRN) and dorsal (DRN) nuclei; the MFC group showed more labeling in the median (MRN), pontine (PRN), magnus (NRM) and obscurus (NRO) nuclei; and the MFSa group had more labeled cells in the pallidus (NRP). The BC exhibited the lowest number of reactive cells. The PRN presented the highest percentage of activation in the raphe while the DRN the lowest. Additional experiments revealed few double-labeled (FOS-IR+5-HT-IR) cells within the raphe nuclei in the MFI group, suggesting little serotonergic activation in the raphe during food ingestion. These findings suggest a differential recruitment of raphe nuclei during various phases of feeding behavior. Such findings may reflect changes in behavioral state (e.g., food-induced arousal versus sleep) that lead to greater motor activation, and consequently increased FOS expression. While these data are consistent with the idea that the raphe system acts as gain setter for autonomic and somatic activities, the functional complexity of the raphe is not completely understood.
Assuntos
Tronco Encefálico/metabolismo , Comportamento Alimentar/fisiologia , Neurônios/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Núcleos da Rafe/metabolismo , Serotonina/metabolismo , Animais , Vias Autônomas/anatomia & histologia , Vias Autônomas/metabolismo , Biomarcadores , Mapeamento Encefálico , Tronco Encefálico/anatomia & histologia , Comportamento Exploratório/fisiologia , Privação de Alimentos/fisiologia , Imuno-Histoquímica , Masculino , Atividade Motora/fisiologia , Núcleos da Rafe/anatomia & histologia , Ratos , Resposta de Saciedade/fisiologia , Regulação para Cima/fisiologiaRESUMO
Systemic ischaemia increases sympathetic activity via both reflex and direct effects on the nervous system, which include the hypothalamus and brainstem structures that provide excitatory drive to sympathetic pre-ganglionic motoneurones. Using an arterially perfused working heart-brainstem preparation (WHBP), we evaluated the sympathoexcitatory response recorded from the thoracic sympathetic chain (tSC) in response to systemic ischaemia (produced by arresting perfusion for 30 s) before and after transecting consecutively at both the ponto-medullary and medullary-spinal cord junctions. Ischaemia produced a striking increase in tSC activity that persisted after transecting at both the ponto-medullary and medullary-spinal cord levels (intact: 70+/-3%; ponto-medullary: 77+/-7%; medullary-spinal cord: 61+/-6%; n=9). In sino-aortic denervated (SAD) rats (n=4), sympathoexcitatory responses were smaller in both intact and ponto-medullary, but not in medullary-spinal cord transected versus intact rats. Following administration of a ganglionic blocker [hexamethonium (hex), 25 mg/kg] after medullary-spinal cord transection the ischaemia-induced sympathoexcitatory response was reduced (12+/-6% increase relative to control, n=4). In medullary-spinal cord transected preparations, intrathecal injection of N2-saturated saline increased tSC discharge (22+/-3%, n=4), which was attenuated by hex (5+/-1%). We propose that neural mechanisms within the cervical-thoracic segments can make a substantial contribution to the sympathoexcitatory response during systemic ischaemia.
Assuntos
Vias Autônomas/fisiologia , Tronco Encefálico/fisiologia , Hipóxia-Isquemia Encefálica/fisiopatologia , Reflexo/fisiologia , Medula Espinal/fisiologia , Sistema Nervoso Simpático/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Adaptação Fisiológica/efeitos dos fármacos , Adaptação Fisiológica/fisiologia , Animais , Vias Autônomas/anatomia & histologia , Pressão Sanguínea/fisiologia , Tronco Encefálico/anatomia & histologia , Denervação , Vias Eferentes/anatomia & histologia , Vias Eferentes/fisiologia , Gânglios Simpáticos/efeitos dos fármacos , Gânglios Simpáticos/fisiologia , Bloqueadores Ganglionares/farmacologia , Parada Cardíaca Induzida , Hexametônio/farmacologia , Bulbo/fisiologia , Neurônios/fisiologia , Ponte/fisiologia , Ratos , Medula Espinal/anatomia & histologiaAssuntos
Humanos , Tórax/anatomia & histologia , Abdome/anatomia & histologia , Pelve/anatomia & histologia , Extremidades/anatomia & histologia , Cabeça/anatomia & histologia , Pescoço/anatomia & histologia , Vias Autônomas/anatomia & histologia , Nervos Cranianos/anatomia & histologia , Ilustração Médica , Anatomia , Anatomia RegionalRESUMO
In this study, we investigated the participation of adrenergic neurotransmission in angiotensin II- (ANGII)-induced water intake and urinary electrolyte excretion by means of injection of the alpha 1-, alpha 2-, and beta-adrenoceptor antagonists and ANGII into the medial preoptic area (MPOA) in rats. Prazosin (an alpha 1-adrenergic antagonist) antagonized the water ingestion, Na+, K+ and urine excretion induced by ANGII, whereas yohimbine (an alpha 2-adrenergic antagonist) enhanced the Na+, K+ and urine excretion induced by ANGII. Propranolol (a nonselective beta-adrenoceptor blocker) antagonized the water ingestion and enhanced the Na+, and urine excretion induced by ANGII. Previous treatment with prazosin reduced the pressor responses to ANGII, whereas yohimbine had opposite effects. Previous injection of propranolol produced no effects in the pressor responses to ANGII. These results suggest that the adrenergic neurotransmission in the MPOA may actively participate in ANGII-induced dipsogenesis, natriuresis, kaliuresis and diuresis in a process that involves alpha 1-, alpha 2-, and beta-adrenoceptors.