Social stress in guinea pigs.

Confrontation studies between eight pairs of two 7-8 months old male guinea pigs, each raised with one female from their 30th day of age, were conducted in an enclosure of 2 m2 in the presence of an unfamiliar female. The opponents were chronically kept together for up to 8 days. When they were not separated after 52 hr, one or (in 1 case) both males fell into a comatose state and died 5-8 days after the onset of the confrontation. Four hr after the onset of the confrontations both opponents showed significantly increased plasma glucocorticoid (CS) titers. At this time as well as 24 hr earlier, prospective winners (PW) and prospective losers (PL) did not yet differ in any physiological parameter measured. Forty-eight hr later, PW were characterized by a low body weight loss, low CS, high testosterone (T) and elevated plasma-catecholamine (CA) values. In contrast, PL showed a high body weight loss, very high CS titers, low T-titers and more elevated CA values than PW. Despite these highly significant differences in physiological parameters, PL and PW did not yet differ in the frequency of any agonistic behavioral element recorded. Seventy-two hr after the onset of the chronic cohabitation, losers began to behave more and more passive, they ceased feeding and drinking and were less and less involved in social interactions. The physiological differences between winners and losers intensified.(ABSTRACT TRUNCATED AT 250 WORDS)