Microinjection of NMDA antagonist into the NTS of conscious rats blocks the Bezold-Jarisch reflex.
The 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.
Chianca
D A
DA
Department of Biological Sciences, Federal University of Ouro Preto, MG, Brazil.
Machado
B H
BH
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000769:Anesthesia, Inhalation; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008845:Microinjections; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors*; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D012018:Reflex / Q000187:drug effects*; D012701:Serotonin / Q000008:administration & dosage; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D017552:Solitary Nucleus / Q000033:anatomy & histology / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D017366:Serotonin Receptor Agonists; D012701:Serotonin; D016202:N-Methylaspartate; D015763:2-Amino-5-phosphonovalerate