Neurotransmission of autonomic components of aortic baroreceptor afferents in the NTS of awake rats.
The effect of sequential blockade of N-methyl-D-aspartic acid (NMDA) receptors with DL-2-amino-5-phosphonopentanoic acid (AP-5) and non-NMDA receptors with 6,7-dinitroquinoxaline-2,3 dione (DNQX) in the nucleus tractus solitarii (NTS) on the cardiovascular responses to electrical stimulation (ES) of the aortic depressor nerve (ADN) was evaluated in awake rats. Two protocols were used. In protocol 1, bilateral microinjection of AP-5 into the NTS (n = 7) reduced the hypotensive response to ES of the ADN; subsequent microinjection of DNQX produced additional reduction in this response. AP-5 reduced the bradycardic response, and DNQX almost abolished this response. In protocol 2, bilateral microinjection of DNQX into the NTS (n = 6) reduced the hypotensive response, and subsequent microinjection of AP-5 significantly reduced this response. DNQX produced a significant reduction in bradycardic response, and AP-5 abolished this response. The data indicate that processing of the parasympathetic component of the NTS aortic baroreceptor afferents is mediated by both NMDA and non-NMDA receptors, whereas processing of the sympathoinhibitory component seems to be only partially mediated by ionotropic receptors.
Machado
B H
BH
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, 14049-900, Ribeirão Preto, São Paulo, Brazil. bhmachad@fmrp.usp.br
Castania
J A
JA
Bonagamba
L G
LG
Salgado
H C
HC
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001011:Aorta / Q000294:innervation*; D001341:Autonomic Nervous System / Q000502:physiology*; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001933:Brain Stem / Q000166:cytology / Q000502:physiology; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D008845:Microinjections; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D011311:Pressoreceptors / Q000502:physiology*; D011810:Quinoxalines / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017552:Solitary Nucleus / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*; D014851:Wakefulness
D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; C056723:FG 9041