Evaluation of nicotinic receptor of pedunculopontine tegmental nucleus in central cardiovascular regulation in anesthetized rat

Objective(s): Cholinergic neurons are important neurons in the Pedunculopontine tegmental nucleus (PPT). In this study, nicotinic receptor of the PPT in central cardiovascular regulation in the anesthetized rat was evaluated. Materials and Methods: Saline, acetylcholine (Ach; doses: 90 and 150 nmol), hexamethonium (Hexa; doses: 100 and 300 nmol) and higher doses of Hexa (300 nmol) + Ach (150 nmol) microinjected into the PPT. The femoral artery was cannulated and cardiovascular responses were continuously recorded by a power lab system. After injection of drugs, peak changes of mean arterial pressure (ΔMAP), systolic blood pressure (ΔSBP) and heart rate (ΔHR) calculated and compared with saline group. Results: The ΔSBP and ΔMAP significantly decreased by two doses of Ach (P<0.05 to P<0.001) but ΔHR did not change. Two doses 100 (P<0.05) and 300 nmol (P<0.01) of Hexa significantly increased ΔHR but did not alter the ΔMAP or ΔSBP. Co-injection of Hexa + Ach significantly strengthened the ΔHR induced by Hexa alone (P<0.01) but did not affect ΔMAP or ΔSBP. Conclusion: These results indicate that nicotinic receptor of the PPT has an inhibitory effect on ΔHR with no significant effect on ΔMAP or ΔSBP.