Role of GABAA receptors of bed nucleus stria terminalis in controlling of blood pressure and heart rate in rats

Introduction: The Bed nucleus stria terminalis (BST) is a part of the limbic system. It was recently shown that chemical stimulation of the BST by L-glutamate elicited cardiovascular depressive responses. In the present study, we have investigated the possible cardiovascular role of the GABAergic receptors in BST by microinjection of its agonist and antagonists. Methods: Experiments were performed on 21 anaesthetized rats. Drugs were microinjected into the BST in volume of 50 nl using streotaxic apparatus. Blood pressure and heart rate were recorded before and throughout each experiment. The averages of maximum changes in the arterial pressure and heart rate were compared with control group and with its average in before injections using student t-test and paired t-test, respectively. Results: GABAA receptor antagonist, bicuculline met iodide (BMI, 1 mM), increased both arterial pressure (+14.2±3.08) and heart rate (+9.8± 2.5) (p<0.05). Muscimole, a GABAA agonist (5 mM), caused a significant decrease of the arterial pressure (-10.2 ±4.1) and heart rate (-20.3±9.40) (p<0.01). However, microinjection of phaclofen (5 mM), a GABAB receptor antagonist caused small unsignificant changes of the heart rate and blood pressure. Conclusion: GABAergic inhibitory neurons of the BST seems to cause decrease in the blood pressure and heart rate by GABAA but not GABAB receptors.