Effects of enkephalin, applied intracellularly, on action potentials in vertebrate A and C nerve fibre axons.
The effects of leucine enkephalin and D-Ala2, Met5 enkephalinamide (DAMA) were tested on the excitability of sciatic nerves in the frog and guinea-pig and vagus nerves in the guinea pig and rabbit. Both enkephalins depressed the amplitude of the compound action potential of A and C fibres. This depression was blocked by small concentrations of naloxone. In the type of experiment carried out, the drugs were added to the cut end of the nerve and the drugs had to reach their site of action in the central bath by diffusion through the axoplasm. This method of application of drug was necessary because enkephalins had no effect on the action potential when applied extracellularly by perfusion. These results demonstrate the presence of stereospecific opioid receptors located on the inner surface of the cell membranes of peripheral vertebrate nerve axons, sensitive to block by some endogenous opioid peptides. A possible physiological role for these intracellular receptors is suggested.
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D004743:Enkephalin, Leucine / Q000494:pharmacology*; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009270:Naloxone / Q000494:pharmacology; D009412:Nerve Fibers / Q000187:drug effects; D009413:Nerve Fibers, Myelinated / Q000187:drug effects; D011817:Rabbits; D011894:Rana pipiens; D012584:Sciatic Nerve; D014630:Vagus Nerve
D009270:Naloxone; D004744:Enkephalin, Methionine; D004743:Enkephalin, Leucine; C022118:enkephalinamide-Met, Ala(2)-