title: Non-opiate beta-endorphin fragments and dopamine--III. gamma-Type endorphins and various neuroleptics counteract the hypoactivity elicited by injection of apomorphine into the nucleus accumbens.
abstract: The hypoactivity in rats induced by small doses of apomorphine, injected bilaterally into the nucleus accumbens area of the brain, could be antagonized by pretreatment with the neuroleptic-like neuropeptide des-enkephalin-gamma-endorphin (DE gamma E, beta-endorphin 6-17) as well as with the neuroleptic drugs haloperidol, sulpiride and clozapine injected into the accumbens. Dose-response studies revealed that a dose of 100 pg DE gamma E completely inhibited the apomorphine-induced hypomotility. The influence of DE gamma E appeared to be specific for gamma-type endorphins, since alpha-type endorphins were inactive in this respect. Treatment with DE gamma E injected into the accumbens for 4 days resulted in an enhancement of apomorphine-induced hypoactivity. It is concluded that gamma-type endorphins may control the activity of dopaminergic transmission in the nucleus accumbens, a suggestion which may be of significance for the purported neuroleptic-like and antipsychotic action of gamma-type endorphins.
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D001058:Apomorphine / Q000008:administration & dosage / Q000037:antagonists & inhibitors*; D004298:Dopamine / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000494:pharmacology*; D007267:Injections; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009714:Nucleus Accumbens; D051381:Rats; D011919:Rats, Inbred Strains; D018823:gamma-Endorphin
chemical_list: D014150:Antipsychotic Agents; D004723:Endorphins; D018823:gamma-Endorphin; D001058:Apomorphine; D004298:Dopamine