EFFECTS OF CORTICOTROPIN-RELEASING FACTOR ON CIRCADIAN LOCOMOTOR RHYTHM IN THE GOLDEN-HAMSTER

Stress produces a reduction in the amplitude of some circadian rhythms . The neurochemical mechanisms underlying stress-induced changes in ci rcadian rhythms are not known. To investigate a possible role of corti cotropin-releasing factor (CRF) in this phenomenon, three related expe riments were carried out activity rhythms of male golden hamsters (10/ 14 hours light/dark entrained, lights on at 0800 h) were measured 1) f ollowing the intracerebroventricular administration of CRF (0.5, 1,0, 2.0, or 4.0 mu g) at two different times of day, 2) following social s tress (30-min resident-intruder confrontation), 3) and following the a dministration of the CRF-antagonist alpha-helical CRF9-41 (2.0 mu g) p rior to a 15-min resident-intruder confrontation. CW produced a signif icant, dose related decrease in circadian rhythm amplitude following a dministration in the morning hours, but not in the afternoon. CRF also induced transient increases in activity post injection concomitant wi th an activation of the hypothalamic-pituitary-adrenocortical (HPA) sy stem. Stress similarly reduced the amplitude of activity pat terns and stimulated the HPA system. The stress-induced depression of circadian rhythm amplitude was significantly attenuated following alpha-helical CRF9-41. These data suggest a role for CRF in the stress-related modu lation of circadian locomotor rhythm amplitude. (C) 1998 Elsevier Scie nce Inc.