Corticosterone facilitates saccharin intake in adrenalectomized rats: Doescorticosterone increase stimulus salience?

Unlike normal rats, adrenalectomized rats do not voluntarily drink sweet sa ccharin solutions. To test whether this is a function of corticosterone in the circulation, and if corticosterone also increases the impetus for drink ing saccharin after a period of withdrawal, we performed the following expe riments. Young male rats were sham adrenalectomized (sham) or adrenalectomi zed (ADX); the ADX rats were provided with subcutaneous pellets containing (percent replacement of corticosterone, %B) 0%B, 15%B, 30%B or 100%B. Sham and ADX rats were immediately provided with saline (0.5%) and saccharin (2 mM) bottles in their home cages. Saccharin was allowed for 4 days on, 3 day s off, 4 days on, 3 days off and a final day on, over the 15 days experimen t. The dose of corticosterone determined both how much saccharin was volunt arily drunk by the ADX rats and the degree of overshoot after days off. Cor ticosterone also determined energy balance of the groups of ADX rats. The 3 0%B pellets restored food intake, body weight gain, insulin and caloric eff iciency to the normal levels observed in sham rats. White fat depot weights and uncoupling protein concentration in brown adipose tissue were restored to sham levels by 100%B, suggesting that these variables which depend on a ctivity in the sympathetic nervous system require considerable glucocortico id receptor occupancy. We conclude that corticosterone increases the willin gness to ingest sweetened water in a unimodal, dose-related manner, while m oderate doses of corticosterone restore energy balance.