role of the nitrergic system of the cuneiform nucleus in cardiovascular responses in urethane-anesthetized male rats

background: the presence of nitric oxide (no) in the cuneiform nucleus (cnf) has been previously shown. in this study, ng-nitro-l-arginine methyl ester (l-name) (an inhibitor of no synthase), l-arginine (l-arg) (a precursor of no), and sodium nitroprusside (snp) (a donor of no) were microinjected into the cnf and cardiovascular responses were investigated. methods: seventy male rats were divided into 7 groups (n=10 each): 1) saline, 2 and 3) l-name (30 and 90 nmol), 4 and 5) l-arg (20 and 60 nmol), and 6 and 7) snp (9 and 27 nmol). after anesthesia, the femoral artery was cannulated and cardiovascular parameters were recorded using a powerlab system. time course changes in mean arterial pressure (δmap) and heart rate (δhr) were calculated and compared with those in the control group (repeated measures anova). maximum ∆map and ∆hr were also compared with those in the control group (independent sample t test). results: ∆map with both doses of l-name (30: p=0.026 and 90: p=0.007) and ∆hr with the higher dose (p=0.034) were significantly higher than those in the control group. maximal ∆map with both doses (p<0.01 and p<0.001, n=10) and maximal ∆hr with the higher dose (p<0.01) were significantly higher than those in the control group. changes in l-arg with both doses were not significantly higher than those in the control group (p=0.26, n=8). ∆map and ∆hr of snp only with the higher dose were significantly lower than those in the control group (p=0.006 and p=0.035), and maximal responses with the higher dose were lower than those in the control group (∆map: p<0.01 and ∆hr: p<0.05, n=7). conclusion: our results showed that the nitrergic system of the cnf had an inhibitory effect on central cardiovascular regulation.