Effects of prepubertal handling on shock-induced fighting and ACTH in male and female rats.

Rats which received either handling from Days 1–14 (EH) or 22–35 (LH) of life or no handling (NH) were tested in the shock-induced fighting situation in adulthood. Ten males and 10 females from each group were either paired for fighting (F), shocked singly (S), or received no shock (N) in the test chamber for 4.5 min in 3 sessions given 48 hr apart. Immediately after the third test session, trunk blood was obtained for determination of plasma ACTH concentrations. Males and females did not differ with respect to fighting frequency in response to shock, but males displayed the fighting posture substantially more than did females. Rats handled either preweaning (EH) or postweaning (LH) fought more often at the two lower shock intensities (0.5 and 1.3 mA) than did nonhandled controls (NH). The incidence of fighting positions did not differ as a function of prior handling. In all groups but one, the pattern of ACTH response to the different test conditions coincided with previous reports: higher levels of ACTH were found in response to shock alone than in response to fighting plus shock, and the lowest levels were found in the nonshocked controls. In the exceptional group, the NH males (but not females), there was a nondiscriminatory ACTH response to the S and F test conditions. The effects of prior handling are discussed in terms of an enhanced coping ability. The results point to the importance of comparing both pre- and postweaning groups when studying the handling phenomenon.