The effect of glutaminergic system on cardiovascular regulation of rat

Introduction: The bed nucleus stria terminalis (BST) is a part of the limbic system, which plays a role in regulation of heart beat and blood circulation. It was recently shown that microinjection of L-glutamate in the BST elicits cardiovascular depressive, but the role of glutamate receptor subtypes has not been investigated yet. In this study, the role of glutamate receptor subgroups in regulation of heart and blood circulation was investigated. Methods: In this experimental study, experiments were performed on 36 anaesthetized and paralyzed rats with Urethane. Drugs were microinjected into the BST in 50 nl volume using streotaxic system. Blood pressure and heart rate were recorded before and after each injection. The average changes in the mean arterial pressure and heart rate at different intervals, were compared both within each case group and between case and control groups using analysis of variance. Results: Microinjection of L-glutamate (0.25 M) into the BST, resulted in a decrease of mean arterial pressure (-25.8±3.7 mmHg) and heart rate (-19.2±3.8 bpm). Injection of AP5, antagonist of glutamate NMDA receptor (2.5mM, 5mM) and CNQX, antagonist of glutamate AMPA receptor (0.5, 1mM) had no remarkable effect on the mean arterial pressure and heart rate. Conclusion: This study shows that activation of glutaminergic system in BST causes decrease of heart rate and mean arterial pressure, which is similar to previous findings, but inhibition of AMPA and NMDA receptors had no effect on mean arterial pressure and heart rate. These findings suggest that the glutaminergic neurons of the BST are quiescent or have little activity to be detected by microinjection of antagonists under these experimental conditions.