Introduction: The cardiovascular effect of the pedunculopontine tegmental nucleus (PPT), a mesencephalic area, has been evaluated. Due to the presence of the GABA_B 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 GABA_A.
Materials and Methods: Rats randomly were divided into control, two doses of 0.5 and 1 nmol of Baclofen (GABA_B receptor agonist), 0.5 and 1 nmol, of Phaclofen (GABA_B receptor antagonist) and two doses of 0.1 and 0.2 nmol of Bicuculline (BMI, GABA_A 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 (Δ,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 ΔMAP, ΔSBP, and ΔHR than control group. Injection of Phaclofen (1nmol) and BMI (0.2 nmol) could increase ΔMAP, ΔSBP, and ΔHR that was non-significant than Phaclofen alone.
Conclusion: We found that GABA_B receptors of the PPT were not involved in cardiovascular activity and this effect was mainly mediated through GABA_A receptors.