Cardiovascular effects of nitrergic system of the pedunculopontine tegmental nucleus in anesthetized rats

OBJECTIVES Nitric oxide (NO) is an important neurotransmitter in central nervous system involved in central cardiovascular regulation. The presence of NO in the pedunculopontine tegmental (PPT) nucleus has been shown, but its cardiovascular effect has not been determined. In the present study, the cardiovascular effect of NO in the PPT nucleus was evaluated. MATERIALS AND METHODS After induction of anesthesia, a polyethylene catheter (PE-50) filled with heparinized saline inserted into the femoral artery, and the blood pressure (BP) and heart rate (HR) were continuously recorded. Animals were then placed in a stereotaxic apparatus and maximum changes of mean arterial pressure (∆MAP) and heart rate (∆HR) after microinjection of two doses of NG-nitro-L-arginine methyl ester (L-NAME, 30 and 90 nmol), L-arginine (L-Arg 10 and 50 nmol) and sodium nitroprusside (SNP, 9 and 27 nmol) into the PPT were provided and compared with control group (One-way ANOVA). RESULTS Both doses of L-NAME significantly increased ∆MAP compared to control (P<0.05 and P<0.01, respectively). ∆HR only in higher dose (90 nmol) significantly increased compared to control (P<0.05). Two doses of L-Arg (10 and 50 nmol/150 nl) had no significant effect on ∆MAP or ∆HR. Higher dose of SNP (27 nmol) significantly decreased ∆MAP (P<0.05) and its both doses significantly decreased ∆HR compared to control (P<0.05 and P<0.001, respectively). Effect of higher dose on ∆HR was significantly higher than the lower dose (P<0.05). CONCLUSION Our results show an inhibitory effect of the nitrergic system of the PPT on central cardiovascular system.