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Development of stress‐induced responses in preweanling rats
Author(s) -
Takahashi Lorey K.,
Turner Joel G.,
Kalin Ned H.
Publication year - 1991
Publication title -
developmental psychobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 93
eISSN - 1098-2302
pISSN - 0012-1630
DOI - 10.1002/dev.420240504
Subject(s) - endocrinology , medicine , hormone , corticosterone , shock (circulatory)
This study examined in postnatal Days 7, 14, and 21 male rats the effects of social isolation and social isolation with administration of brief foot shocks on the development of stress‐induced behavioral and pituitary‐adrenal hormone responses. Day 21 rats appeared similar to adult rats in their responses to the two test conditions. That is, exposure to either isolation or to shock increased both pituitaryadrenal hormone secretion and tail‐flick latencies but only administration of shock potentiated freezing and ultrasonic vocalizations. Younger rats differed from Day 21 rats in their responses to the two test conditions. In both tests, Day 7 rats produced the highest number of ultrasounds, which may be due to a significant decrease in body temperature. In contrast, in Day 14 pups, exposure to shock significantly reduced isolation‐induced ultrasonic vocalizations. Additional age‐dependent differences were found in the analgesic responses of Days 7 and 14 rats. Day 7 rats exposed to stress became consistently hyperalgesic whereas Day 14 rats showed only a short‐lasting analgesic response. Although in Days 7 and 14 rats exposure to the two stress conditions produced significant elevations in pituitary‐adrenal hormone concentrations, plasma levels were lower than those measured in Day 21 rats. To summarize, preweanling rats exhibit varied age‐dependent responses when exposed to different stress environments.