Effects of oestradiol and progesterone on stress-induced secretion of prolactin in ovariectomized and/or adrenalectomized female rats.

Prolactin (Prl) secretion in response to an acute stress was studied in ovariectomized (OVX) and/or adrenalectomized (ADX) adult female rats, nontreated or injected sc with a single dose of 5 micrograms oestradiol-17 beta benzoate (OB) or 2 mg progesterone (P). The stress applied consisted of cutting the tip of tail of conscious animals. Radioimmunoassay was used to measure Prl in the serum prepared from blood collected by decapitation 10 min following the stress, i.e., at the point of maximum recorded Prl response. It was found that the capacity of the animals to secrete large quantities of Prl under stress was, when compared to that in intact controls, markedly reduced in OVX or ADX rats and substantially absent in OVX + ADX rats. A 10-fold increase of basal serum Prl, similar in magnitude to the increase in intact controls, was induced by the stress in OVX animals pretreated with OB. On the contrary, pretreatment of OVX animals with P resulted in a complete block of the Prl response to the stress. The stimulative effect of OB was greatly attenuated in stressed OVX + ADX rats. The results suggest that OB potentiates whereas P attenuates the stress-induced secretion of Prl in the female rat, and that the potentiating effect of OB is dependent on functionally intact adrenals.