EFFECT OF NITRIC-OXIDE INHIBITION ON CAPSAICIN-ELICITED VASODILATION IN THE RAT ORAL CIRCULATION

The effects of local application of capsaicin on the vascular conducta nce of the oral structures (upper gingiva, lower gingiva, tongue, righ t and left submandibular glands) were studied with and without pretrea tment with N-G-nitro-L-arginine methyl ester (L-NAME), a potent inhibi tor of nitric oxide formation in rats. Alterations in tissue blood flo w were measured by laser-Doppler-flowmetry; systemic blood pressure wa s monitored continuously during the experiments. Local, application of increasing concentrations of capsaicin (1.0; 3.33; 10.0; 33.3 mM; in a volume of 5 mu l) resulted in a dose-dependent increase in the vascu lar conductance of all tissues investigated. There was a significant c orrelation between the values obtained for vascular conductance in the right and the left submandibular glands. Bolus intravenous injection of L-NAME (10 mg kg(-1)) elevated the mean systemic blood pressure sig nificantly, by about 20%, with a rapid onset. This increase persisted until the end of the experiment. The augmentation of vascular conducta nce elicited by 10.0 mM capsaicin, locally administered, was significa ntly diminished in animals pretreated with L-NAME in all tissues teste d. The results indicate that nitric oxide formation plays a significan t role in the enhancement of vascular conductance produced in rat oral structures by local capsaicin administration.