Nmda receptors in the nucleus tractus solitarii are involved in the
bradycardic but not in the pressor response to carotid chemoreceptor
activation.
Haibara, Andr[acute]ea S., Eduardo Colombari, Deocl[acute]ecio A.
Chianca, Jr, Leni G. H. Bonagamba, and Benedito H. Machado.
Department of Physiology, School of Medicine of Ribeirao Preto,
University of Sao Paulo, 14049-900, Ribeirao Preto, SP, Brazil
APStracts 2:0133H, 1995.
Activation of carotid chemoreceptors with potassium cyanide (KCN, iv)
produces increases in arterial pressure, bradycardia and tachypnea.
In the present study we activated carotid chemoreceptors with KCN and
the neurotransmission of the chemoreceptor reflex into the
commissural NTS was blocked with AP-5, a NMDA selective antagonist.
The aim of this study was to evaluate the involvement of NMDA
receptors in the cardiovascular and respiratory responses produced by
chemoreceptor activation in unanesthetized rats. The pressor response
to KCN was not changed after microinjection of three different doses
of AP-5 into the NTS, while the bradycardic response was reduced in a
dose-dependent manner. The increase in respiratory frequency in
response to carotid chemoreceptor activation was also not affected by
AP-5 microinjected into the NTS. The data indicate that the
activation of the cardiovagal component of the chemoreflex in the
commissural NTS is mediated by NMDA receptors, while pressor and
ventilatory responses are not.
Received 27 September 1994; accepted in final form 20 March 1995.
APS Manuscript Number H871-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 19 April 1995.