Involvement of different opioid receptor subtypes in electric shock-induced analgesia and motor suppression in the rat.
We have investigated the correlation of electric shock-induced behavioral changes and functional alterations of endogenous opioid receptor subtypes. The degree of electric shock-induced behavioral changes, such as analgesia and motor suppression, was dependent on the duration of and time after electric shock application. The electric shock-induced behavioral changes were completely antagonized by naloxone. The apparent development of tolerance to both behavioral effects as a result of successive daily electric shock was different: Tolerance to electric shock-induced analgesia developed after 2 days' successive electric shock application, while tolerance to motor suppression was not observed even after 7 days' successive electric shock application. There was a decrease of [3H][D-Ala2, Met5]enkephalinamide ([3H]DAMEA, delta agonist) binding and an increase of [3H]naloxone (mu antagonist) binding when potent electric shock-induced analgesia developed. On the other hand, the binding of [3H]DAMEA and [3H]ethylketocyclazocine (kappa agonist) was significantly changed when locomotion was suppressed. These results suggest strongly that different opioid systems may participate in electric shock-induced analgesia and motor suppression: electric shock-induced analgesia and motor suppression may be mediated by mu/delta and kappa/delta receptors, respectively.
D000818:Animals; D003496:Cyclazocine / Q000031:analogs & derivatives / Q000378:metabolism; D004597:Electroshock; D004744:Enkephalin, Methionine / Q000031:analogs & derivatives / Q000378:metabolism; D016314:Ethylketocyclazocine; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009270:Naloxone / Q000378:metabolism / Q000494:pharmacology; D010146:Pain / Q000503:physiopathology*; D010622:Phencyclidine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011957:Receptors, Opioid / Q000502:physiology*; D013997:Time Factors
D011957:Receptors, Opioid; D009270:Naloxone; D004744:Enkephalin, Methionine; D016314:Ethylketocyclazocine; C022118:enkephalinamide-Met, Ala(2)-; D010622:Phencyclidine; D003496:Cyclazocine