Evaluation of the cardiovascular effect of GABAB receptor of the Pedunculopontine tegmental nucleus (PPT) in anesthetized rats

Introduction:The cardiovascular effect of the pedunculopontine tegmental nucleus (PPT), a mesencephalic area, has been evaluated.Due to the presence of the GABAB receptor of GABAergic system in the PPT, this study has investigated the possible cardiovascular effect of this receptor in the PPT and has compared it with GABAA.Methods: Rats randomly were divided into control, two doses of 0.5 and 1 nmol of Baclofen (GABAB receptor agonist), 0.5 and 1 nmol, of Phaclofen (GABAB receptor antagonist) and two doses of 0.1 and 0.2 nmol of Bicuculline (BMI, GABAA receptor antagonist) and co-injection of Phaclofen (1nmol)+ Bicuculline (0.2 nmol) groups.After anesthesia, a heparinized polyethylene catheter was placed in the femoral artery and was connected to a pressure transducer cardiovascular response was recorded by a Power lab device.Then the systolic blood pressure (SBP), mean arterial pressure (MAP) and heart rate (HR) were continuously recorded.The injection of drugs into the PPT was done stereotaxically.Cardiovascular changes (,difference between pre and post-injection) induced by drug were calculated and analyzed.Results: Injection of both doses of Baclofen and Phaclofen did not induce significant changes in MAP, SBP, and HR.Injection of both doses of BMI significantly increased MAP, SBP, and HR than control group.Injection of Phaclofen (1nmol) and BMI (0.2 nmol) could increase MAP, SBP, and HR that was non-significant than Phaclofen alone. Conclusion:We found that GABAB receptors of the PPT were not involved in cardiovascular activity and this effect was mainly mediated through GABAA receptors.