title: NMDA receptor antagonist blocks the bradycardic but not the pressor response to L-glutamate microinjected into the nucleus tractus solitarius (NTS) of unanesthetized rats.
abstract: In the present study we evaluated the role of NMDA receptors on the pressor and bradycardic responses to L-glutamate (L-Glu) microinjected into the nucleus tractus solitarius (NTS) of unanesthetized rats. L-Glu (1 nmol/100 nl) was microinjected into the NTS before and 10 min after microinjection of phosponovaleric acid (AP-5), a selective NMDA receptor antagonist, into the NTS of three different groups of rats (0.5, 2.0 and 10.0 nmol/100 nl). Microinjection of AP-5 into the NTS produced a dose-dependent reduction in the bradycardic response to L-Glu. However, no significant change in the pressor response to L-Glu was observed. These results indicate that the activation of the cardiovagal component (bradycardia) by L-Glu involves NMDA receptors and suggest that the activation of the sympatho-excitatory component (pressor response) by L-Glu in the commissural NTS is mediated by non-NMDA receptors.
authors.affiliation: Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
authors.forename: E
authors.initials: E
authors.lastname: Colombari
authors.forename: L G
authors.initials: LG
authors.lastname: Bonagamba
authors.forename: B H
authors.initials: BH
authors.lastname: Machado
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D018691:Excitatory Amino Acid Antagonists / Q000008:administration & dosage / Q000494:pharmacology; D018698:Glutamic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects*; D008297:Male; D008845:Microinjections; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D015763:2-Amino-5-phosphonovalerate