NMDA receptor antagonist blocks the bradycardic but not the pressor response to l-glutamate microinjected into the nucleus tractus solitarius (NTS) of unanesthetized rats

• Published in: Brain research 1997-02, Vol.749 (2), p.209-213
• Main Authors: Colombari, Eduardo, Bonagamba, Leni G.H., Machado, Benedito H.
• Format: Article
• Language: English
• Subjects: 2-Amino-5-phosphonovalerate - administration & dosage; 2-Amino-5-phosphonovalerate - pharmacology; Animals; Autonomic regulation; Blood Pressure - drug effects; Cardiovagal excitation; Cardiovascular regulation; Excitatory Amino Acid Antagonists - administration & dosage; Excitatory Amino Acid Antagonists - pharmacology; Excitatory amino acid receptor; Glutamic Acid - administration & dosage; Glutamic Acid - pharmacology; Heart Rate - drug effects; Male; Microinjections; Phosphonovaleric acid; Rats; Rats, Wistar; Receptors, N-Methyl-D-Aspartate - antagonists & inhibitors; Solitary Nucleus - drug effects; Solitary Nucleus - physiology; Sympatho-excitation; Time Factors
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/S0006-8993(96)01169-9

In the present study we evaluated the role of NMDA receptors on the pressor and bradycardic responses to l-Glutamate ( l-G1u) 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.