Neonatal corticoid administration: retardation of adrenal rhythmicity and desynchronization of puberty.

The development of the adrenal corticosterone and progesterone diurnal rhythms was retarded by a single injection of cortisol acetate, dexamethasone acetate or progesterone into 3-day-old female rats. This effect was transient with the establishment of the corticosterone rhythm by day 70. The retardation of adrenal hormone rhythmicity may alter the normal process of sexual maturation, because cortisol and dexamethasone-treated animals but not progesterone treated rats exhibited a desynchronization of the events associated with puberty. Vaginal opening was delayed, and dissociated from first ovulation in these rats. Further, neonatal cortisol administration lengthened the estrous cycle in adulthood. It can be concluded from our study that the maturation of the neural centers controlling adrenal steroid secretion may be essential for the proper timing of pubertal events in the female rat.