The effect of gamma-type endorphins on alpha-MSH release in the rat.
Neuroleptic drugs increase the level of alpha-melanotropin (alpha-MSH) in the blood of the rat. We have investigated whether neuroleptic-like peptides, the gamma-type endorphins, also affect alpha-MSH release. A structure-activity study revealed that (des-enkephalin)-gamma-endorphin (DE gamma E, beta-LPH-(66-77), beta-endorphin-(6-17)) is able to increase plasma alpha-MSH levels after intracerebroventricular injection, while the longer gamma-type endorphins, i.e. gamma E (beta-LPH-(61-77)), beta-endorphin-(1-17)), and DT gamma E (beta-LPH-(62-77), beta-endorphin-(2-17)) were without effect in the dosage used. A dose-response study revealed a more or less bell-shaped relationship for the effect of DE gamma E on plasma alpha-MSH levels. The effect of DE gamma E could not be counteracted by apomorphine or naloxone. The observations indicate that DE gamma E increases plasma alpha-MSH levels in a way distinct from that of haloperidol and the opiate peptide beta-endorphin. On the other hand, a time-course of plasma alpha-MSH levels after DE gamma E administration resembled the one which has been seen after haloperidol injection. From experiments performed on pituitary neurointermediate lobes incubated in vitro, it seems not likely that DE gamma E acts directly on the dopamine receptors of the pituitary in affecting alpha-MSH release. In conclusion, it appears that DE gamma E affects alpha-MSH levels in plasma in a way distinct from that of the neuroleptic drug haloperidol and of the opiate-peptide beta-endorphin.
A A
AA
de Rotte
T B
TB
van Wimersma Greidanus
M
M
van de Buuse
E A
EA
Andringa-Bakker
D
D
de Wied
D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D001058:Apomorphine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000008:administration & dosage / Q000494:pharmacology*; D006220:Haloperidol / Q000494:pharmacology; D007276:Injections, Intraventricular; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000097:blood / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D001615:beta-Endorphin; D018823:gamma-Endorphin
D014150:Antipsychotic Agents; D004723:Endorphins; D009270:Naloxone; D001615:beta-Endorphin; D018823:gamma-Endorphin; C033558:des-enkephalin-gamma-endorphin; D009074:Melanocyte-Stimulating Hormones; D006220:Haloperidol; D001058:Apomorphine