The central role of corticotrophin‐releasing factor (CRF‐41) in psychological stress in rats.

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Abstract
1. We investigated the central role of corticotrophin‐releasing factor (CRF‐41) in psychological stress‐induced responses, including cardiovascular, thermoregulatory and locomotive activity in free‐moving rats. 2. Psychological stress was induced by cage‐switch stress. After rats were placed in the novel environment, blood pressure, heart rate, body temperature and locomotive activity significantly increased. The intracerebroventricular (I.C.V.) injection of alpha‐helical CRF(9‐41), a CRF‐41 receptor antagonist, significantly attenuated the stress‐induced hypertension, tachycardia, hyperthermia and increase in locomotive activity. However, in unstressed rats, the I.C.V. injection of alpha‐helical CRF(9‐41) had no effect on physiological parameters measured in this study. 3. In unstressed rats, the I.C.V. injection of CRF‐41 (1 microgram and 10 micrograms) increased blood pressure, heart rate, body temperature and locomotive activity in a dose‐dependent manner. The changes in these responses were quite similar to those observed during cage‐switch stress. 4. The results suggest that central CRF‐41 plays an important role in psychological stress‐induced hypertension, hyperthermia, tachycardia and increase in locomotive activity. However, it is likely that central CRF‐41 does not contribute to normal cardiovascular and body temperature regulation when rats are free from stress.