Interaction between gabaergic and opioid pathways in the regulation of gonadotropin secretion in males

Opioid and cocaine combined effect on cocaine-induced changes in HPA and HPG axes hormones in men

Nalbuphine, a mixed micro-/kappa-opioid analgesic, may have potential as a new medication for the treatment of cocaine abuse. Kappa-opioid agonists functionally antagonize some abuse-related and locomotor effects of cocaine, and both kappa-selective and mixed micro-/kappa-opioids reduce cocaine self-administration by rhesus monkeys. Because cocaine's interactions with the hypothalamic-pituitary-adrenal and (HPA) hypothalamic-pituitary-gonadal (HPG) axes may contribute to its reinforcing properties, we examined the effects of cocaine alone and in combination with nalbuphine. Neuroendocrine effects of a single dose of cocaine alone (0.2 mg/kg, IV), with nalbuphine (5 mg/70 kg, IV)+cocaine (0.2 mg/kg, IV) in combination were compared in seven adult men (ages 18-35) who met DSM-IV criteria for current cocaine abuse. Cocaine alone, and in combination with nalbuphine was administered on separate test days under placebo-controlled, double blind conditions. Cocaine stimulated ACTH, cortisol, and LH, whereas cocaine+nalbuphine in combination produced a smaller increase in ACTH, and decreased cortisol and LH. Thus it appears that nalbuphine attenuated cocaine's effects on ACTH, cortisol, and LH. These data are consistent with our earlier report that nalbuphine modestly attenuated cocaine's positive subjective effects, and that the subjective and cardiovascular effects of cocaine+nalbuphine in combination were not additive.

Effect of naloxone on the pulsatile secretion of luteinizing hormone in gonadectomized male and female ferrets before and after oestradiol replacement

Abstract Intravenous infusions of the opioid receptor antagonist, naloxone, caused a significant rise in luteinizing hormone (LH) pulse frequency in male and female ferrets which had been gonadectomized 10 days earlier while in breeding condition; mean LH concentrations and LH pulse amplitudes were not affected. By contrast, naloxone failed to stimulate LH pulse frequency, or other LH parameters in gonadectomized ferrets of either sex which received daily injections of a low dose of oestradiol. Our results for the ferret, in which the female is an induced ovulator, resemble those previously obtained in another induced ovulator, the rabbit. They contrast, however, with the results of numerous studies using spontaneously ovulating species in which sex steroids, if anything, facilitate the ability of naloxone to stimulate LH secretion.