EFFECTS OF NALOXONE ON MEMBRANE-POTENTIAL OF IDENTIFIED NEURONS OF HELIX-ASPERSA

1. The action of naloxone, at doses that antagonize the inhibitory actions of opioid agonists in mammals, was tested in identified cells of Helix aspersa. 2. Naloxone was able to modify the membrane potential of some cells without prior exposure to opiate agonists. Some cells were depolarized and others were hyperpolarized. 3. Met-enkephalin was also effective in eliciting changes in membrane potential of some cells, and failed in others, some of which responded to naloxone, and was able to partially antagonize the effect of naloxone. 4. The electrophysiological responsiveness of this preparation to opioid agonists and antagonists makes this mollusc a suitable model for the study of opioid dependence and naloxone pharmacology.