ABSTRACT
Background: The ventral tegmental area [VTA] is well known for its role in cardiovascular control. It is demonstrated that about 20-30% of the VTA neurons are GABAergic though their role in cardiovascular control is not yet understood. This study is carried out to find the effects of GABA A and GABA B receptors on cardiovascular response of the VTA
Methods: Experiments were performed on urethane anesthetized male Wistar rats. Drugs were microinjected unilaterally into the VTA. The average changes in mean arterial pressure [MAP] and heart rate [HR] were compared between the case and the control groups using t test and with the pre-injection values using paired t test
Results: Microinjection of muscimol, a GABAA agonist [500, 1500 and 2500 pmol/100nl] into the VTA had no significant effect on MAP and HR compared with the saline group and preinjection values. Injection of bicuculline methiodide [BMI, 100 and 200 pmol/100 nl], a GABAA antagonist, caused a significant increase in the MAP [11.1 +/- 1.95mmHg, P<0.5] and a decrease in HR [-32.07 +/- 10.2, P<0.01]. Microinjection of baclofen a GABAB receptor agonist [500 or 1000 pmole/100 nl] and phaclofen a GABAB receptor antagonist [500 or 1000 pmole/100 nl] had no significant effects on MAP and HR
Conclusion: For the first time it was demonstrated that GABA system of the VTA inhibits the cardiovascular system through the activation of GABAA but not the GABAB receptors