Social stress during pregnancy and lactation affects in guinea pigs the male offsprings ' endocrine status and infantilizes their behaviour

This study investigated the influence of the social environment during preg nancy and lactation on the male offsprings' endocrine parameters and behavi our in guinea pigs. The subjects studied were sons whose mothers had either lived in a stable social environment during pregnancy and lactation or in an unstable social environment during this period of life. The stable socia l environment was made by keeping the group composition (one male, five fem ales) constant; in the unstable social environment situation every third da y, two females from different groups were exchanged. After weaning, seven g roups of sons, whose mothers had lived in an unstable social environment an d seven groups of sons, whose mothers had lived in a stable social environm ent, consisting of two males each, were established. From their 20th throug h their 100th day of age the spontaneous behaviour of the males was recorde d in their home cages. On the endocrine level, cortisol- and testosterone-c oncentrations in serum as well as adrenal tyrosine hydroxylase activities w ere determined. Sons, whose mothers had lived in an unstable social environ ment, showed significantly higher amounts of resting with bodily contact th an sons, whose mothers had lived in a stable social environment. Additional ly, they displayed this behaviour to an older age than the latter sons. Fur theron, sons, whose mothers had lived in an unstable social environment, di splayed significantly higher frequencies of courtship behaviour than sons, whose mothers had lived in a stable social environment, which was integrate d into play behaviour. These behavioural data point to an infantilization o f sons, whose mothers had lived in an unstable social environement. The beh avioural patterns corresponded with a delayed development of the hypothalam o-pituitary-adrenocortical-axis and a lower activity of the sympathetic-adr enomedullary-system compared to sons whose mothers had lived in a stable so cial environment. Testosterone did not differ between both categories of ma les. Thus, the instability of the social environment during pregnancy and l actation had distinct and not yet described effects on the behaviour and en docrine system of the male offspring. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.