Adrenal influence on the persistence of pseudopregnancy in rats

The effect of adrenalectomy on the duration of pseudopregnancy was investigated in rats. When adrenalectomy was performed three days before cervical stimulation or when it was done on the first day (day 1, day of estrus) or day 2 of pseudopregnancy, the duration of the pseudopregnancy was significantly prolonged (3.0, 2.5 and 1.8 days respectively). This effect of adrenalectomy was not seen when operation was delayed until day 4 of pseudopregnancy. Adrenalectomy on day 2 of pseudopregnancy significantly increased prolactin (PRL) release at the time of the nocturnal PRL surge (5:00) on day 7. When rats were ovariectomized simultaneously with adrenalectomy on day 1, the stimulating effect of adrenalectomy on PRL release was more evident. The effect of active immunization against corticosterone on the continuation of pseudopregnancy was also examined. Neutralization of plasma corticosterone extended the duration of pseudopregnancy and the binding activity of the antiserum positively correlated with the length of continuing diestrus (P < 0.05). These results indicate the negative effect of the adrenal glands, which is probably due to corticosterone, on PRL release in pseudopregnant rats and that the early relief of this inhibition extends the duration of pseudopregnancy.