DECREASED BRAIN REWARD PRODUCED BY ETHANOL WITHDRAWAL

Abstinence from chronic administration of various drugs of abuse such as ethanol, opiates, and psychostimulants results in withdrawal syndro mes largely unique to each drug class. However, one symptom that appea rs common to these withdrawal syndromes in humans is a negative affect ive/motivational state. Prior work in rodents has shown that elevation s in intracranial self-stimulation (ICSS) reward thresholds provide a quantitative index that serves as a model for the negative affective s tate during withdrawal from psychostimulants and opiates. The current study sought to determine whether ICSS threshold elevations also accom pany abstinence from chronic ethanol exposure sufficient to induce phy sical dependence, Rats prepared with stimulating electrodes in the lat eral hypothalamus were trained in a discretetrial current-intensity IC SS threshold procedure; subsequently they were subjected to chronic et hanol administration in ethanol vapor chambers (average blood alcohol level of 197 mg/dl). A time-dependent elevation in ICSS thresholds was observed following removal from the ethanol, but not the control, cha mbers. Thresholds were significantly elevated for 48 hr after cessatio n of ethanol exposure, with peak elevations observed at 6-8 hr. Blood alcohol levels were directly correlated with the magnitude of peak thr eshold elevation. Ratings of traditional overt signs of withdrawal sho wed a similar time course of expression and resolution. The results su ggest that decreased function of reward systems (elevations in reward thresholds) is a common element of withdrawal from chronic administrat ion of several diverse classes of abused drugs.