AROUSAL FOLLOWING INTRA-PREOPTIC AREA ADMINISTRATION OF NALTREXONE, ICI 174864 OR NOR-BNI IN HIBERNATING GROUND-SQUIRRELS

Experiments were performed from January 1 to 30 January, 1989. Drugs w ere administered to the preoptic area of hibernating ground squirrels through a chronically implanted cannula on the 2nd day of a torpor bou t. When naltrexone (an antagonist of opioid receptor) was injected, pa rt (naltrexone, 0.5 or 1 mug/mul/32 min) or all (naltrexone, 2 mug/mul /32 min) of the animals' body temperature was increased and they arous ed from hibernation within 20 h after the injection. Further experimen ts showed that intra-preoptic area perfusion of 1 nmol of ICI 174864 ( an antagonist of delta receptor) or nor-BNI (an antagonist of kappa re ceptor), but not beta-FNA (an antagonist of mu receptor), were able to increase the body temperature of hibernating ground squirrels and aro use them from hibernation in 20 h after the injection. These results i ndicate that (1) opioid peptides in the preoptic area may be involved in the mechanisms of hibernation; (2) activation of delta and kappa re ceptors in the preoptic area is indispensable for the maintenance of h ibernation in ground squirrels.