Involvement of nitric oxide in parasympathetic and antidromic vasodilatations in cat lower lip

The involvement of nitric oxide (NO) in the lower lip vasodilatations mediated via parasympathetic and antidromic mechanisms was examined in alpha-chloralose/urethane-anesthetized cats, with the two types of blood flow responses being recorded separately (by laser Doppler flowmeter) from the two sides of the lower lip. The central cut end of the lingual nerve (LN) or the peripheral cut end of the inferior alveolar nerve (IAN) was electrically stimulated to elicit parasympathetic or antidromic vasodilatation, respectively, in the lower lip. N(G)-nitro-L-arginine methyl ester (L-NAME), but not N(G)-nitro-D-arginine methyl ester (D-NAME) (each at 30 mg/kg), markedly reduced the increases in lip blood flow evoked by stimulation, the reduction being to a similar degree irrespective of whether LN or IAN was stimulated. Pretreatment with L-arginine did not prevent the L-NAME-induced attenuation of either type of vasodilatation. In conclusion, these results suggest that synthesized NO may have a common site of action in antidromic and parasympathetic vasodilator pathways to the cat lower lip.