Hélder Mauad

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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(More)
The cardioinhibitory effects of cardiac vagal motoneurons (CVMs) are mediated by activation of postganglionic neurons in the epicardial ganglia which have been shown to exert functionally selective effects on heart rate and atrioventricular conduction in the rat. Here we investigate whether CVMs producing these responses may occupy different rostrocaudal(More)
Anatomical studies have demonstrated the existence of purinergic P2 receptors in the nucleus ambiguus (NA), a site containing cardiac vagal motoneurons. However, very little is known about the functional role of these receptors in central cardiac vagal regulation. The aims of our study were to evaluate the following: (1) the blood pressure and heart rate(More)
The maintenance of arterial pressure at levels adequate to perfuse the tissues is a basic requirement for the constancy of the internal environment and survival. The objective of the present review was to provide information about the basic reflex mechanisms that are responsible for the moment-to-moment regulation of the cardiovascular system. We(More)
Stimulation of the periaqueductal gray matter (PAG) and the deeper layers of superior colliculus (SC) produces both freezing (tense immobility) and flight (trotting, galloping and jumping) behaviors along with exophthalmus (fully opened bulging eyes) and, less often, micturition and defecation. The topography of these behaviors within the distinct layers of(More)
Microinjection of L-glutamate into the lateral commissural nucleus tractus solitarii (NTS) of unanesthetized rats evokes increases in mean arterial pressure (MAP) and a bradycardia. In a previous study we verified that this increase in MAP is mediated sympathetically because prazosin (i.v.) blocks this response. The aim of the present study was to evaluate(More)
Microinjection of L-glutamate into the nucleus tractus solitarii (NTS) of conscious freely moving Wistar rats (240-260 g) produces pressor (+48 +/- 4 mmHg) and bradycardic (-153 +/- 20 bpm) responses. In the present study L-glutamate (2.5 nmol/100 nl) was microinjected before and after microinjection of increasing doses of glycine (10, 25 and 50 nmol/100(More)
The present study examined the role of the sympathetic system and pulmonary afferent feedback in the baroreflex inhibition by chemical stimulation of the dorsal periaqueductal gray matter (DPAG) of the anesthetized rat. The baroreflex bradycardia was induced by phenylephrine infusions (PHE, 50 μg/ml/min, i.v.) given either alone or combined with glutamate(More)
Earlier studies report that sinoaortic baroreceptor denervation (SAD) in rats causes moderate elevation of mean arterial pressure along with a marked increase of arterial pressure lability (APL). In this context, we studied the effects of selective aortic denervation (AD) or selective carotid denervation (CD) on the regulation of blood pressure. In(More)
The contribution of alpha(2)-receptor mechanisms in the rostral ventrolateral medulla (RVLM) in mediating the enhanced renal excretory responses evoked by the intravenous infusion of the alpha(2)-receptor agonist xylazine was examined in ketamine-anesthetized rats. In ketamine-anesthetized rats, the bilateral microinjection of the alpha(2)-receptor(More)