Background
The dorsomedial periaqueductal gray (dmPAG) is a mesencephalic area and has numerous functions including cardiovascular regulation. Because nitric oxide (NO) is present in the dmPAG, here we investigate, the probable cardiovascular effect of NO in the dmPAG.
Methods
Five groups (n = 6 for each group) were used as follows: (1) control; (2) L‐NAME (NG‐nitro‐L‐arginine methyl ester, a NO synthase inhibitor, 90 nmol); (3) L‐arginine (L‐Arg, a precursor for NO, 60 nmol); (4) Sodium nitroprusside (SNP, a NO donor, 27 nmol); and (5) L‐Arg + L‐NAME. The cardiovascular parameters were recorded by a Power Lab device after cannulation of the femoral artery. Drugs were injected using a stereotaxic instrument. The changes (∆) in systolic blood pressure (SBP), mean arterial pressure (MAP), and heart rate (HR) were calculated at different times and compared to the control group.
Results
Microinjection of L‐NAME significantly increased ∆SBP, ∆MAP, and ∆HR more than saline (from p < 0.05 to p < 0.001). L‐Arg only significantly increased ∆HR (p < 0.05). In the L‐Arg + L‐NAME group, the above parameters also significantly increased (from p < 0.01 to p < 0.05) but not as significantly as with L‐NAME alone. Microinjection of SNP significantly decreased ∆SBP and ∆MAP more than in the control and L‐NAME groups (from p < 0.01 to p < 0.001), but ∆HR did not change significantly.
Conclusion
The results indicated that NO in dmPAG has an inhibitory effect on cardiovascular responses in anesthetized rats.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.