Effects of acute and chronic administrations of naloxone on plasma luteinizing hormone and prolactin in broody turkey hens (Meleagris gallopavo)

Abstract

The effects of acute and chronic administration of naloxone, an opioid antagonist, on luteinizing hormone (LH) and prolactin concentrations were investigated in broody turkey hens. Naloxone failed to induce any changes in the plasma prolactin concentrations in the hens. On the other hand, an intravenous injection of naloxone (6 mg kg−1 BW) decreased plasma concentrations of LH. Conversely, LH concentrations were significantly increased after infusing 10 μg h−1 of naloxone for 7 d. No changes in behavioral pattern, feed intake and water consumption were observed during and following infusion of naloxone in comparison with controls. These results indicate that a role of the endogenous opioids in the modulation of LH release cannot be excluded and further investigations are needed to clarify this relationship. On the other hand, there is little support for any role of opioids in the maintenance of the high level of prolactin concentrations associated with the expression of broodiness. Key words: Naloxone, luteinizing hormone, prolactin, broody turkey hens