The amygdala mediates the impairing effect of the selective kappa-opioid receptor agonist U-50,488 on memory in CD1 mice.

The effect of the selective kappa-opioid receptor agonist U-50,488 on passive avoidance behaviour was studied in CD1 mice bearing lesions of the amygdaloid complex. The results have shown that post-trial injections of U-50,488 in unoperated mice as well as lesions of the amygdaloid complex in untreated mice decreased retention performances. No further impairment was observed in lesioned mice treated with U-50,488, indicating that amygdala is involved in the mediation of the effects of kappa-opioid receptor agonists on memory. The possibility that kappa-opioid receptors could modulate the memory retention of CD1 mice by influencing their emotional state is discussed.