Possible Interaction: Naloxone and Progesterone

“The opioid antagonist, naloxone , causes an increase in luteinizing hormone secretion, particularly during the luteal phase.”

“Pharmacological blockade of inhibitory neural pathways with NG-…-arginine methyl ester (nitric oxide synthase inhibitor), naloxone (opioid receptor antagonist), apamin or suramin plus pyridoxal phosphate-6-azophenyl-2′,4′-disulphonic acid (P2 …) counteracted the inhibitory effect of submaximally (10 µM), but not maximally (30 µM), effective concentrations of progesterone.”

“To maintain lactation, pups (1-3 days old) were replaced every 24 h, and 4 days after the cesarean eight pups were … maintain a strong suckling stimulus during the following 24 h. Naloxone administration significantly reduced serum prolactin levels in control (cholesterol) rats but progesterone … naloxone and this … estrogen.”

“ Progesterone treatment to intact androgenized rats significantly increased prolactin levels and the administration of naloxone blocked the stimulatory effect of the steroid.”

“ Naloxone treatment at either 1.1 (Nal-1) or 2.0 (Nal-2) mg/kg BW significantly increased circulating progesterone within 15 min of i.v.”

“ NAL suppressed the PRL response to NMA in OVX gilts pretreated with oil vehicle or progesterone , indicating that NMA stimulation of PRL secretion is mediated through the EOP system.”

“The data suggested that progesterone suppression of tonic LH secretion, before oestradiol injection, was completely antagonized by naloxone.”

“GnRH efflux from the SME of gilts during the luteal and late follicular phases was augmented in the presence of NAL.”

“Thus, the level of estradiol and progesterone at different stages of the estrous cycle may affect the female rat's response to the satiety effect of naloxone.”

“In oestrogen-primed animals similar treatment with naloxone (0.4 and 5 mg/kg) stimulated LH secretion but the increase was significantly smaller than that observed after injecting progesterone.”