EVIDENCE THAT ENDOGENOUS CORTICOTROPIN-RELEASING FACTOR SUPPRESSES BEHAVIORAL-RESPONSES OF GUINEA-PIG PUPS TO BRIEF ISOLATION IN NOVEL SURROUNDINGS

Guinea pig pups were injected subcutaneously with a corticotropin-rele asing factor antagonist (CRF12-41) or saline vehicle and then placed i nto a novel cage for 30 or 60 min. Isolated 20- to 26-day-old pups voc alized more and exhibited more locomotor activity when given 15 to 150 mu g of CRF12-41 than when given saline. The presence of the mother i n the test cage prevented the antagonist fl om affecting behavior. The influence of the antagonist during isolation was not limited to guine apigs near weaning age: CRF12-41 increased levels of vocalizing in iso lated, 4- to 6-day-old pups, though no changes were seen in locomotor activity. Results support the hypothesis that endogenous corticotropin -releasing factor, perhaps acting at a peripheral binding site, suppre sses the active behavioral response characteristic of pups during the early phase of isolation in novel surroundings. (C) 1997 John Wiley & Sons, Inc.