The effects of neuropeptides on discrete-trial conditioned avoidance responding.
The effects of intracerebroventricular administration of several peptides on discrete-trial, conditioned avoidance responding were assessed in the rat. Three peptides (neurotensin, bombesin and beta-endorphin) produced a neuroleptic-like effect (i.e. a decrease in avoidance responding with no effect on escape responding). A low dose (0.6 nmol) of each peptide elicited a significant effect. Neurotensin and bombesin produced a significant but partial decrease in avoidance responding; larger doses of these peptides did not produce a greater effect. beta-Endorphin elicited dose-related decrements in avoidance responding. In addition, the effect of neurotensin, but not bombesin or beta-endorphin, was antagonized by simultaneous administration of an equimolar dose of thyrotropin-releasing hormone. Hence, the 3 peptides do not appear to produce decreases in avoidance responding by the same mechanism. Thyrotropin-releasing hormone, luteinizing hormone-releasing hormone, bradykinin, substance P, des-Tyr1-gamma-endorphin and melanotropin inhibiting factor did not significantly affect avoidance responding. These findings, taken together with previous findings, suggest that intracerebroventricular administration of certain endogenous peptides (neurotensin, bombesin and beta-endorphin) may exert neuroleptic-like effects.
D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects*; D001839:Bombesin / Q000494:pharmacology*; D001920:Bradykinin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004723:Endorphins / Q000494:pharmacology*; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D009496:Neurotensin / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D013373:Substance P / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology; D001615:beta-Endorphin
D004723:Endorphins; D010446:Peptide Fragments; D010455:Peptides; D013373:Substance P; D007987:Gonadotropin-Releasing Hormone; D009496:Neurotensin; D013973:Thyrotropin-Releasing Hormone; D001615:beta-Endorphin; C018903:gamma-endorphin, des-Tyr(1)-; D009074:Melanocyte-Stimulating Hormones; D001839:Bombesin; D001920:Bradykinin