Endocrine Abstracts

Early life events have special importance in the development and may affect the lifetime vulnerability to diseases. For correct interpretation of the long-term consequences it is crucial to understand the immediate effects. The role of vasopressin in hypothalamo-pituitary-adrenal axis regulation as well as in stress-related affective disorders is important therefore we addressed the question if the lack of this hormone will modify the perinatal stress reactivity.

Vasopressin producing (di/+) and deficient (di/di) Brattleboro rat pups were used. The separation of the 9-day-old pups from their mother for 24 h resulted in a remarkable corticosterone elevation in both genotypes without an ACTH increase in di/di rats. As the time-course of ACTH and corticosterone can be different we examined the 1-4-12-24 h separation period, too, with similar result (no ACTH elevation at any time point in di/di rats parallel with a remarkable corticosterone increase). Altered sensitivity of the adrenal gland might also explain the findings, so we examined adrenal secretion in vivo with exogenous ACTH administration, but failed to find a significant difference between the genotypes. Tenth postnatal day is in the middle of the stress hyporesponsive period so we examined earlier (4–5 day old) and later (20 day old) postnatal phases too. After 24 h separation the ACTH levels did not change in di/di, but increased in di/+ pups with the highest rise at 10 days old, although corticosterone was significantly higher in both genotype at each time-point.

We can conclude that the role of vasopressin is an important factor in ACTH-secretion regulation during the postnatal period. However in the absence of ACTH other secretagogues may become important in the regulation of the adrenal gland secretion. The marked corticosterone elevation in the absence of ACTH rise is possibly not due to the different time-course of the two hormones or an altered sensitivity of the gland and it is present during the whole postnatal period up to 20 day.