Navegando por Autor "DiMicco, Joseph A."
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Item Cardiovascular and thermal responses evoked from the periaqueductal grey require neuronal activity in the hypothalamus.(2009) Menezes, Rodrigo Cunha Alvim de; Zaretsky, Dmitry V.; Fontes, Marco Antônio Peliky; DiMicco, Joseph A.Stimulation of neurons in the lateral/dorsolateral periaqueductal grey (l/dlPAG) produces increases in heart rate (HR) andmean arterial pressure (MAP) that are, according to traditional views, mediated through projections to medullary autonomic centres and independent of forebrain mechanisms. Recent studies in rats suggest that neurons in the l/dlPAG are downstream effectors responsible for responses evoked from the dorsomedial hypothalamus (DMH) from which similar cardiovascular changes and increase in core body temperature (Tco) can be elicited.We hypothesized that, instead, autonomic effects evoked from the l/dlPAG depend on neuronal activity in the DMH. Thus, we examined the effect of microinjection of the neuronal inhibitor muscimol into the DMH on increases in HR, MAP and Tco produced by microinjection of N-methyl-d-aspartate (NMDA) into the l/dlPAG in conscious rats. Microinjection of muscimol alone modestly decreased baseline HR and MAP but failed to alter Tco. Microinjection of NMDA into the l/dlPAG caused marked increases in all three variables, and these were virtually abolished by prior injection of muscimol into the DMH. Similar microinjection of glutamate receptor antagonists into theDMHalso suppressed increases inHR and abolished increases in Tco evoked from the PAG. In contrast, microinjection of muscimol into the hypothalamic paraventricular nucleus failed to reduce changes evoked from the PAG and actually enhanced the increase in Tco. Thus, our data suggest that increases in HR, MAP and Tco evoked from the l/dlPAG require neuronal activity in the DMH, challenging traditional views of the place of the PAG in central autonomic neural circuitry.Item The dorsomedial hypothalamus and the central pathways involved in the cardiovascular response to emotional stress.(2011) Fontes, Marco Antônio Peliky; Custódio, Carlos Henrique Xavier; Menezes, Rodrigo Cunha Alvim de; DiMicco, Joseph A.Psychological stress elicits increases in sympathetic activity accompanied by a marked cardiovascular response. Revealing the relevant central mechanisms involved in this phenomenon could contribute significantly to our understanding of the pathogenesis of stress-related cardiovascular diseases, and the key to this understanding is the identification of the nuclei, pathways and neurotransmitters involved in the organization of the cardiovascular response to stress. The present review will focus specifically on the dorsomedial hypothalamus, a brain region now known to play a primary role in the synaptic integration underlying the cardiovascular response to emotional stress.