HORMONAL PATTERN OF THE PHEROMONAL RESTORATION OF CYCLIC ACTIVITY IN AGING IRREGULARLY CYCLING AND PERSISTENT-ESTRUS FEMALE RATS

This study reports the hormonal pattern of pheromonal restoration of c yclic activity (PRCA) in irregularly cycling (IC) and in anovulatory p ersistent-estrus (PE) aging female middle-aged Wistar rats. Hypothalam ic content of LHRH and plasma levels of LH, FSH, estradiol (E(2)), and progesterone (P) were measured by RIA methods, and prolactin (PRL) wa s examined by ELISA in 1) normal four-day cycling rats, 2) saline-trea ted IC and PE rats, and 3) IC and PE rats treated with sprays of male urine (50 mu l every 10 min for 1 h on only one day, at a distance of 1 cm from the nostrils). Group 1 showed low levels of LHRH and high le vels of LH, FSH, E(2), P, and PRL in the afternoon of proestrus (PR). In group 2, the pattern was not cyclical and the levels of the hormone s were higher than basal for the cyclic rats, except for P, which was lower. Group 3 showed a depletion of the hypothalamic LHRH and an incr ease in plasma LH, FSH, E(2), P, and PRL. FSH, E(2), and P showed the strongest rise, leading to an elevated ratio of FSH to LH. Four-day es trous cycles reappeared in urine-treated rats on the succeeding days. The cyclic behavior of the PRCA hormones was, qualitatively, the same as in the normally cycling rats. According to the results, the origin of the PRCA effect is an olfactory input to the hypophysiotropic area of the hypothalamus. The findings corroborate our previous data on est rous cycles and extend the male pheromonal effect on aging females to an ''olfactory'' regulation of the endocrine activity of the hypothala mic-pituitary-ovarian axis.