Navegando por Palavras-chave "Bezold-Jarisch reflex"

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    Ablation of NK1 receptor bearing neurons in the nucleus of the solitary tract blunts cardiovascular reflexes in awake rats
    (Elsevier B.V., 2006-11-13) Abdala, Ana Paula L.; Schoorlemmer, Gerhardus Hermanus Maria [UNIFESP]; Colombari, Eduardo; Universidade Federal de São Paulo (UNIFESP); Univ Estadual Paulista
    The nucleus of the solitary tract (NTS) receives primary afferents involved in cardiovascular regulation. We investigated the role of NK1-receptor bearing neurons in the NTS on cardiovascular reflexes in awake rats fitted with chronic venous and arterial cannulae. These neurons were lesioned selectively with saporin conjugated with substance P (SP-SAP, 2 mu M, bilateral injections of 20 nL in the subpostremal NTS, or 200 nL in both the subpostremal and the commissural NTS). Before, and 7 and 14 days after injection of SP-SAP, we measured changes in blood pressure and heart rate induced by i.v. injection of phenylephrine and nitroprusside (baroreceptor reflex), cyanide (arterial chemoreceptor reflex), and phenylbiguanide (Bezold-Jarisch reflex). the smaller injections with SP-SAP completely abolished NK1 receptor staining in the subpostremal NTS. the larger injections abolished NK1 receptor immunoreactivity in an area that extended from the commissural NTS to the rostral end of the subpostremal NTS. the lesions seemed to affect only a limited number of neurons, since neutral red stained sections did not show any obvious reduction in cell number. the smaller lesions reduced the gain of baroreflex bradycardia and the hypotension induced by phenylbiguanide. the larger lesions completely abolished the response to phenylbiguanide, blocked the baroreflex bradycardia induced by phenylephrine, severely blunted the baroreflex tachycardia, and blocked the bradycardia and reduced the hypertension induced by cyanide. Thus, these responses depend critically on NK1-receptor bearing neurons in the NTS. (c) 2006 Elsevier B.V. All rights reserved.
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    Autonomic processing of the cardiovascular reflexes in the nucleus tractus solitarii
    (Assoc Bras Divulg Cientifica, 1997-04-01) Machado, B. H.; Mauad, H.; Chianca, D. A.; Haibara, A. S.; Colombari, Eduardo [UNIFESP]; UNIV FED ESPIRITO SANTO; UNIV FED OURO PRETO; Universidade Federal de São Paulo (UNIFESP)
    The nucleus tractus solitarii (NTS) receives afferent projections from the arterial baroreceptors, carotid chemoreceptors and cardiopulmonary receptors and as a function of this information produces autonomic adjustments in order to maintain arterial blood pressure within a narrow range of variation. The activation of each of these cardiovascular afferents produces a specific autonomic response by the excitation of neuronal projections from the NTS to the ventrolateral areas of the medulla (nucleus ambiguus, caudal and rostral ventrolateral medulla). The neurotransmitters at the NTS level as well as the excitatory amino acid (EAA) receptors involved in the processing of the autonomic responses in the NTS, although extensively studied, remain to be completely elucidated, In the present review we discuss the role of the EAA L-glutamate and its different receptor subtypes in the processing of the cardiovascular reflexes in the NTS. The data presented in this review related to the neurotransmission in the NTS are based on experimental evidence obtained in our laboratory in unanesthetized rats. The two major conclusions of the present review are that a) the excitation of the cardiovagal component by cardiovascular reflex activation (chemo- and Bezold-Jarisch reflexes) or by L-glutamate microinjection into the NTS is mediated by N-methyl-D-aspartate (NMDA) receptors, and b) the sympatho-excitatory component of the chemoreflex and the presser response to L-glutamate microinjected into the NTS are not affected by an NMDA receptor antagonist, suggesting that the sympatho-excitatory component of these responses is mediated by non-NMDA receptors.
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    The bradycardic and hypotensive responses to serotonin are reduced by activation of GABA(A) receptors in the nucleus tractus solitarius of awake rats
    (Assoc Bras Divulg Cientifica, 2005-07-01) Callera, Joao Carlos; Colombari, Eduardo [UNIFESP]; De Luca, Laurival Antonio; Menani, Jose Vanderlei; UNESP; Universidade Federal de São Paulo (UNIFESP)
    We investigated the effects of bilateral injections of the GABA receptor agonists muscimol (GABA(A)) and baclofen (GABA(B)) into the nucleus tractus solitarius (NTS) on the bradycardia and hypotension induced by iv serotonin injections (5-HT, 2 mu g/rat) in awake male Holtzman rats. 5-HT was injected in rats with stainless steel cannulas implanted bilaterally in the NTS, before and 5, 15, and 60 min after bilateral injections of muscimol or baclofen into the NTS. the responses to 5-HT were tested before and after the injection of atropine methyl bromide. Muscimol (50 pmol/50 nl, N = 8) into the NTS increased basal mean arterial pressure (MAP) from 115 4 to 144 6 mmHg, did not change basal heart rate (HR) and reduced the bradycardia (-40 +/- 14 and -73 +/- 26 bpm at 5 and 15 min, respectively, vs -180 +/- 20 bpm for the control) and hypotension (-11 +/- 4 and -14 +/- 4 mmHg, vs -40 +/- 9 mmHg for the control) elicited by 5-HT. Baclofen (12.5 pmol/50 nl, N = 7) into the NTS also increased basal MAP, but did not change basal HR, bradycardia or hypotension in response to 5-HT injections. Atropine methyl bromide (1 mg/kg body weight) injected iv reduced the bradycardic and hypotensive responses to 5-HT injections. the stimulation of GABAA receptors in the NTS of awake rats elicits a significant increase in basal MAP and decreases the cardiac Bezold-Jarisch reflex responses to iv 5-HT injections.