Activities of the pituitary–adrenal and gonadal axes during the estrous cycle in adult female rats prenatally exposed to morphine

The present investigation concerns 80–90-day-old female rats born from morphine-exposed mothers (2×10 mg/kg per day from day 11–18 of gestation) or saline-treated ones (controls). The former showed reduced size and activity of the adrenals at birth. At adult stage, they present: (1) higher increase of plasma adrenocorticotrophic hormone level on proestrus; (2) significant rise of plasma corticosterone level on diestrus morning and estrus evening; (3) adrenal atrophy which was significant only on diestrus and estrus morning; (4) more corticosterone binding sites of type I (mineralocorticoid receptors) on proestrus morning in the hippocampus; (5) more corticosterone binding sites of type II (glucocorticoid receptors) in the hippocampus on proestrus morning and in the hypothalamus on estrus morning. In both experimental groups, B_max for hypothalamic mineralocorticoid receptors were drastically higher on estrus morning than on the other stages of the estrous cycle. The activity of the pituitary–gonadal axis is poorly affected by prenatal morphine-exposition. In both experimental groups drastic and comparable surges of both plasma progesterone and luteinizing hormone were observed during proestrus. Nevertheless morphine-exposed females showed higher levels of plasma estradiol on diestrus morning but lower levels on metestrus morning. In conclusion, prenatal exposition to morphine has long-term effects mainly on pituitary–adrenal axis as well as on binding sites for corticosterone in the hypothalamus and the hippocampus which are dependent on the estrous cycle stages in adult females.