Role of opiates in the physiological control of prolactin in man

The Authors, for testing the opiate receptors role in human PRL secretion, performed the following experiment: they administered: 1) to 24 women during day 2 and 4 of the puerperium, divided into 3 groups of 8 subjects, respectively 5, 10, 20 mg naloxone. 2) to 16 women during day 3 and 4 of the puerperium, divided into 2 groups of 8 subjects, during mechanical breast stimulation with a breast pump (10 min for each breast), respectively 5, 10 mg naloxone. 3) to 12 women in physiological menopause, in basal condition and after administration of oestradiol 17-n-valerate 4 mg/die over ten days, 10 mg naloxone. 4) to 7 women in physiological menopause, in basal condition and after administration of ethinyl-oestradiol 50 micrograms/die over ten days, 5 mg morphine hydrochloride. They observed that naloxone is not able to reduce either basal PRL secretion in menopausal women, or puerperal hyperprolactinemia, or PRL release induced by mechanical breast stimulation. On the contrary, an exogenous opiate administration produced a PRL significant increase (P less than 0.01) and such increase has been affected in a statistically significant way (P less than 0.05) by the oestrogen rate.