Prolactin-releasing effect of tryptolines in the developing and adult male and female rats

Abstract

The developmental prolactin-releasing effect of Tryptoline (T), Methoxytryptoline (MT) and Hydroxytryptoline (OHT) was examined comparatively in male and female rats. A single injection of T 15 mg/Kg increased serum prolactin in both sexes; the increase was significant from day 20 onwards. OHT evoked a sharp rise in 12 day-old rats and the releasing effect increased with age, both in males and females. No significant sex differences were observed in T or OHT treated rats. MT caused an increment in prolactin secretion in male rats and this action increased with age. The releasing effect of MT was not significant in females, even at 38 postnatal days. In adult animals, the tryptolines (15 mg/Kg) were able to increase serum prolactin in males and in females in diestrous; a dose of 5 mg/Kg of T was only effective in adult male rats. The prolactin-releasing effect was drastically reduced by orchidectomy and by ovariectomy. LH, FSH and TSH were not modified by any treatment. The present results show for the first time the ontogeny of the prolactin-releasing effect of tryptolines in male and female rats and that this effect depends on the presence of gonadal secretions in adults.