Cardiovascular effects of nitrergic system of the pedunculopon-tine tegmental nucleus in anesthetized rats

Objective(s): 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-۵۰) 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, ۳۰ and ۹۰ nmol), L-arginine (L-Arg ۱۰ and ۵۰ nmol) and sodium nitroprusside (SNP, ۹ and ۲۷ 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 (PP<۰.۰۱, respectively). ∆HR only in higher dose (۹۰ nmol) significantly increased compared to control (P<۰.۰۵). Two doses of L-Arg (۱۰ and ۵۰ nmol/۱۵۰ nl) had no significant effect on ∆MAP or ∆HR. Higher dose of SNP (۲۷ nmol) significantly decreased ∆MAP (P<۰.۰۵) and its both doses significantly decreased ∆HR compared to control (PP<۰.۰۰۱, respectively). Effect of higher dose on ∆HR was significantly higher than the lower dose (P<۰.۰۵). Conclusion: Our results show an inhibitory effect of the nitrergic system of the PPT on central cardiovascular system.

Keywords:

blood pressure , L-NAME , Microinjection , Nitric oxide , Pedunculopontine tegmental , Sodium nitroprusside