The Role of Nitric Oxide in the Dorsolateral Periaqueductal Grey in the Central Regulation of Cardiovascular Activity in Rat

Nitric oxide (NO) is an important neurotransmitter in the central nervous system which is involved in different processes like cardiovascularregulation. The presence of nitrergic neurons in the dorsolateral periaqueductal grey (dlPAG) has been determined. However, the impact of the nitrergic system of dlPAG in central cardiovascular regulation is unknown. In the current study, we aimed to evaluate the cardiovascular responses by microinjecting NGnitro- L-arginine methyl ester (L-NAME) (an inhibitor of NO synthase) and L-arginine (L-Arg) (a precursorof NO) into dlPAG. Materials and Methods: Eighteen male Wistar rats were divided into 3 groups: 1) Control, 2) L-NAME (90 nmol), and 3) L-Arg (60nmol). After anesthesia with urethane (1.5 g/kg, i.p), the femoral artery was isolated and cannulated with angiocath. Theskull was drilled using stereotaxy over dlPAG. The considered drugs were microinjected into the dlPAG using a micropipette. The cardiovascular parameters including systolic blood pressure (SBP), mean arterial pressure (MAP), and heart rate (HR) were evaluatedby Lab Chart software. The data was obtained and comparison was performed by repeated measures ANOVA test. Results: Our findings showed that the HR in the L-Arg group significantly decreased and in the L-NAME group significantly increased as compared tothe control group. In addition, the vascular parameters including SBP and MAP meaningfully increased in the considered groups in comparison with the control group. Conclusion: According to our results, we suggest that the nitrergic neurons of the dlPAG is involved in centralcardiovascular regulation.