Naloxone reversal of stress-induced suppression of LH release in the common marmoset.

There is considerable evidence suggesting that endogenous opioid peptides (EOP) might play a role in the defensive response to stressful stimuli. The stress associated with receipt of aggression from a female conspecific and physical restraint for collection of serial blood samples (at 10-min intervals) resulted in a significant (p less than 0.05) suppression of LH secretion in the oestradiol primed ovariectomized marmoset. Administration of the opioid receptor antagonist, Naloxone (1 mg/kg) immediately before and after receipt of aggression completely prevented the stress-induced decrease in LH release. This suggests that EOP may mediate, at least in part, this stress induced decline in LH release in the marmoset.