Neuropeptides and social behavior of rats tested in dyadic encounters.
The effects of various neuropeptides on social behavior was studied in a test procedure in which 7-day isolated animals were tested together with non-isolated partners in dyadic encounters. The short-term isolation procedure increased the frequency and duration of social activities of the rats, but hardly affected non-social explorative behaviors of the animals. Systemic injection of certain neuropeptides, i.c. prolyl-leucyl-glycinamide (PLG), thyrotropin releasing hormone (TRH) and the ACTH 4-9 analog ORG 2766, reversed the isolation-induced increase in social activity, similarly as previously observed with antidepressant drugs. Subcutaneous treatment with beta-endorphin, alpha-endorphin and des-Tyr-gamma-endorphin increased social interactions in 7-day isolated animals. beta-Endorphin enhanced social behavior of non-isolated rats as well, whereas gamma-MSH decreased the social interactions of these animals. Both peptides affected especially social contact behavior. The potent action of beta-endorphin suggests that this peptide and opioid systems may play a physiological role in social behavior. It is proposed that a possible functional antagonism between ACTH-like peptides, especially gamma-MSH, and beta-endorphin may operate in social behavior. The action of the peptides may be rather specific for social behavior, since none of the neuropeptides affected non-social explorative behaviors of the rats during the social interaction test.
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000378:Agonistic Behavior / Q000187:drug effects; D000818:Animals; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology; D004723:Endorphins / Q000494:pharmacology; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012919:Social Behavior; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D001615:beta-Endorphin
D004723:Endorphins; D009419:Nerve Tissue Proteins; D001127:Arginine Vasopressin; C015119:argipressin, des-GlyNH2(9)-; D010121:Oxytocin; D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone; D009074:Melanocyte-Stimulating Hormones; D009075:MSH Release-Inhibiting Hormone