Effects of naloxone and electroacupuncture treatment on plasma concentrations of LH in sheep

Abstract

Mature ewes were injected intravenously with the opioid antagonist naloxone (1.1 mg/kg) during the breeding season. Ewes with luteal phase concentrations of plasma progesterone responded with a significant (P less than 0.05) increase in plasma LH 14-23 min after naloxone injection. In contrast, non-luteal ewes with low plasma progesterone did not respond to injection of naloxone with an LH increase. Similar treatment of castrated males (wethers) with this dosage of naloxone failed to increase plasma LH. Electroacupuncture (EA) treatment of luteal phase ewes prevented the ability of exogenous naloxone to increase plasma LH. Treatment of wethers by EA decreased significantly (P less than 0.01) their high basal concentrations of plasma LH, but similar EA treatment of intact ewes did not change their low basal concentrations of LH.