Alcohol alliesthesia: Food restriction increases the palatability of alcohol through a corticosterone-dependent mechanism

The present article analyzed the dramatic increase in alcohol ingestion tha t is known to occur in laboratory rats subjected to food restriction. Ln th e first experiment, we wished to know when during the day food restricted a nimals consume the "extra" alcohol ration. Determinations of ethanol drinki ng at 3-h intervals throughout the day revealed that although food-restrict ed animals drink much ethanol at all times of the day, they retain a defini te daily rhythm such that peak intake occurs during the dark hours. The sec ond experiment tested the hypothesis that chronic food restriction is accom panied by positive alliesthesia for the taste of alcohol. To answer this qu estion, we employed the taste reactivity method to measure hedonic and aver sive reactions to 6% ethanol as a function of nutritional status. It was fo und that two weeks of food restriction, which approximately doubled the vol untary intake of ethanol, was associated with a significant increase in the hedonic response elicited by intraoral infusions of ethanol. Alcohol also elicited fewer aversive responses in food restricted subjects. Because chro nic food restriction increases adrenal corticosterone secretion, we used th e corticosterone synthesis inhibitor metyrapone as a tool to assess the imp ortance of adrenal corticosterone secretion for the increased palatability of alcohol observed during food restriction. The third experiment demonstra ted that attenuation of corticosterone synthesis significantly reduced the hedonic taste reactions to alcohol observed in food-restricted rats; this d rop in alcohol taste reward was accompanied by a nonsignificant increase in the aversive reaction to alcohol. The final experiment investigated the ef fect of prolonged exposure to exogenous corticosterone on the taste reactiv ity to ethanol in freely fed subjects. Adrenalectomized animals bearing cor ticosterone implants for 3 weeks found the taste of alcohol more pleasant t han did intact or adrenalectomized rats implanted with blank pellets. Taken together, the present results suggest that food restriction is associated with an apparent increase in the sensory reward-positive alliesthesia-deriv ed from alcohol; this effect appears to be mediated by increased adrenal co rticosterone secretion. (C) 1999 Elsevier Science Inc.