[The potential-dependent action of the opioid peptide dermorphin]

Dermorphin action was studied on cross-section strip of frog stomach muscle by a mechanographic recorder. The results show that dermorphin (10(-5)-10(-8) M) blocks acetylcholine effects, spontaneous activity and muscle contractions induced by direct electrical stimulation. All the above effects are hardly reversible. Dermorphin fails to block spontaneous and evoked activities if it is injected into the incubated medium during K(+)-depolarization (KCI--100 mM) of the muscle. Thus, dermorphin has voltage-dependent action. The discussion deals with dermorphin action on voltage-dependent Ca(2+)-channels of muscle cell membrane.