Dermorphin inhibits micturition reflex in rats at a central site of action.

Intrathecal dermorphin (0.8-80 ng) or [D-Ala2, D-Leu5]-enkephalin (DADLE, 5.7-171 ng) produced a dose-related marked inhibition of reflex micturition in urethane-anesthetized rats until voiding was suppressed and overflow incontinence ensued. These effects of dermorphin or DADLE were promptly abolished by i.v. naloxone (0.2 mg/kg). The inhibitory effect of dermorphin but not that of DADLE was partially prevented by systemic capsaicin desensitization (50 mg/kg s.c., 4 days before). Intravenous dermorphin had little or no effect on micturition up to 8 micrograms/kg.