AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 4 1065-R1070, Copyright © 1994 by American Physiological Society
Both NMDA and non-NMDA receptors in the NTS participate in the baroreceptor reflex in rats
H. Ohta and W. T. Talman
Department of Neurology, University of Iowa, Iowa City.
In this study, we determined whether either N-methyl-D-aspartate (NMDA)
receptors or non-NMDA receptors in the nucleus tractus solitarii (NTS)
participate in the baroreceptor reflex in rats. Microinjection of an NMDA
receptor antagonist, MK-801, and a non-NMDA receptor antagonist,
6,7-dinitroquinoxaline-2,3-dione, into the NTS decreased the sensitivity of
the baroreceptor reflex by 51 and 41%, respectively. Simultaneous
administration of both agents further reduced the sensitivity of the
baroreceptor reflex to 28% of control. A competitive NMDA receptor
antagonist, 2-amino-5-phosphonovaleric acid, also attenuated reflex
bradycardia or tachycardia elicited by a single dose of phenylephrine or
nitroprusside, respectively. Specificity of each antagonist's effects was
supported by selective blockade of depressor responses produced by agonists
that act at the NMDA and non-NMDA receptors, respectively. Results of this
study indicate that both non-NMDA- and NMDA-sensitive receptors are
involved in baroreceptor reflex transmission in the NTS.
