Glutaminergic receptor in the rostroal ventrolateral medulla mediate the cardiovascular responses to activation of the bed nucleus of the stria terminalis in female ovariectomized rat

Introduction: Experiments were done to investigate the cardiovascular response to glutamate (Glu) injection in the bed nucleus of stria terminalis (BST) in urethane anesthetized ovariectomized (OVX) or OVX estrogen  treated (OVX+E)  female Wistar rats. In this study also the effect of glutaminergic system of the rostral ventrolateral medulla (RVLM) on Glu stimulation of cardiovascular response of the BST were investigated. Methods: Experiments were performed on 27 anaesthetized rats divided into two groups of ovarictomized (OVX) and ovarictomized-estrogen treated (OVX+E). Drugs (50 nl), glutamate; (Glu 0.25M/20 nl) was microinjected into the BST and kynurenic acid a nonselective antagonist glutamate receptors (KYN, 5mM/ 50 nl), was microinjected into the RVLM by micropipette and the BST was restimulated at 10, 20, 60 minutes after the injection of KYN into the RVLM. Blood pressure and heart rate were recorded before and throughout each experiment. The means of maximum changes of mean arterial pressure and heart rate were compared between groups of OVX and OVX+E and saline using ANOVA and with preinjection values using paired t- test. Results: Unilateral microinjection of Glu into the BST (control) decreased mean arterial pressure and heart rate, in the OVX+E and OVX. Ipsilateral microinjection of KYN into the RVLM attenuated Glu induced depressor and bradycardic responses to stimulation of the BST 10 minutes after microinjection of KYN in both groups. Conclusion: These data suggest that RVLM cardiovascular sympathetic premotor neurons contain glutamate receptors that mediate in part the depressor and bradycardic responses to stimulation of the BST in the OVX and OVX+E animals.