Diazepam: endocrine effects and hypothalamic binding sites in the developing male and female rat

The ontogeny of diazepam's endocrine effects in male and female rats, and of 3H-diazepam binding in the hypothalami of both sexes was studied. Diazepam inhibited basal prolactin levels in 38 day-old male rats and, if prolactin levels were stimulated by Haloperidol the inhibition occurred in 28 day-old males, indicating that the hypoprolactinemic effect of the drug could be evidenced earlier if prolactin titers were high. The prolactin inhibition in females did not reach statistical significance at any studied age. Diazepam significantly released LH only in male rats at 12 days, showing thus, a period of special sensitivity of LH release to the drug. Benzodiazepine-hypothalamic binding sites increased in number from birth to puberty, reaching a plateau at 20 days of age. No sexual differences or changes in affinity were found throughout the studied period. These results suggest that the maturation of diazepam's hypoprolactinemic effect could be partially related to the increase in hypothalamic binding sites, whereas the sexual differences observed in diazepam's endocrine actions could be due to sexual differentiation of endocrine control mechanisms.