The Torpedo electric organ is a model for opiate regulation of acetylcholine release.

Acetylcholine release from the nerve terminals of the purely cholinergic Torpedo electric organ is inhibited by morphine in a dose-dependent, naloxone-reversible fashion. In addition, it is shown that this preparation contains an enkephalin-like substance which, like acetylcholine, is present in a high concentration at the nerve terminals. These findings and the chemical homogeneity of the electric organ nerve terminals render this preparation an excellent model for the study of opiate regulation of neurotransmitter release.