• D A Chianca and B H Machado.
• Department of Biological Sciences, Federal University of Ouro Preto, MG, Brazil.
• Brain Res. 1996 Apr 29; 718 (1-2): 185-8.

AbstractThe purpose of the present study was to evaluate whether or not cardiovagal excitatory and sympatho-inhibitory pathways of the Bezold-Jarisch reflex at the NTS level were mediated by NMDA receptors. The Bezold-Jarisch reflex was activated by intravenous (i.v.) injection of serotonin in conscious rats before and after microinjection of phosphonovaleric acid (AP-5) a selective NMDA antagonist, into the NTS. The Bezold-Jarisch reflex was also activated before and after methyl-atropine (i.v.) in order to evaluate if the changes in mean arterial pressure were dependent on the bradycardic response. The data showed that AP-5 into the NTS produced a dose-dependent reduction in both bradycardic and hypotensive responses to activation of the Bezold-Jarisch reflex. Methyl-atropine also blocked the bradycardic and hypotensive responses to Bezold-Jarisch reflex activation. The data show that in conscious rats the cardiovagal component of the Bezold-Jarisch reflex plays a major role in the cardiovascular changes produced by the activation of this reflex and suggest that the neurotransmission of the cardiovagal component of the Bezold-Jarisch reflex is mediated by NMDA receptors.

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