The motor effect of the capsaicin-sensitive inhibitory innervation of the rat ureter.

Neurokinins activate a series of tetrodotoxin (TTX)-insensitive rhythmic contractions of the rat isolated ureter. Field stimulation or capsaicin (1-3 microM) produced a transient inhibition of neurokinin-activated ureteral motility in preparations from control but not from capsaicin-pretreated (50 mg/kg s.c.) rats. The inhibitory action of field stimulation but not that of capsaicin was prevented by TTX. It is concluded that a capsaicin-sensitive inhibitory innervation exists in the rat ureter.