Brain oxytocin augments stress-induced long-lasting plasma adrenocorticotropic hormone elevation in rats.

Toshihiro Nakashima, Tohru Noguchi, Tomonori Furukawa, Michiyo Yamasaki, Shinya Makino, Seiji Miyata, Toshikazu Kiyohara

Index: Neurosci. Lett. 321(3) , 161-4, (2002)

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Abstract

Single stress induces long-lasting changes in the hypothalamo-pituitary--adrenal (HPA) axis of adult animals. Selective oxytocin (OXT) receptor antagonist was administrated into the cerebroventricle of male rats to test its influence on plasma adrenocorticotropic hormone (ACTH) responses induced by immobilization stress. The ACTH level is significantly higher than the control level (P<0.05) up to 6 days after single stress. Although the OXT antagonist did not change the plasma ACTH level at the end of single stress (P=0.59), the antagonist significantly decreased the ACTH concentration at the end of repeated (3 days) stress and 2 days after single stress (P<0.05) compared with controls. The results suggest that endogenous brain OXT enhances the long-lasting but not immediate HPA axis response to stress.