Behavioral changes after chronic ethanol treatment.

Rats were maintained on ad lib food and a forced-intake regimen of ethanol for up to 270 days. Termination of the long-term ethanol treatment caused two types of withdrawal syncromes. The first, an acute withdrawal syndrome was observed within 12 hr after the discontinuation of the ethanol treatment and was characterized by extreme hyper-excitability. The second, a delayed withdrawal syndrome was characterized by a more coordinated behavioral stimulation and developed first after about 3 days after the discontinuation of the ethanol treatment. Bilateral application of dopamine (DA) into the nucleus accumbens of both chronic ethanol and ethanol rats undergoing withdrawal produced a pronounced increase in coordinated locomotor activity which was 8-10 times higher than that of untreated water control rats. This phenomenon was observed first after 5 months of ethanol treatment and lasted for about 4 weeks after the termination of the treatment. This effect of DA was antagonized by haloperidol indicating a specific effect on DA-receptors. It is concluded that prolonged ethanol administration produces an increased sensitivity of the DA- receptors in the nucleus accumbens and further supports the contention that central catecholamine mechanisms are involved in the mediation of the withdrawal syndrome observed after long-term treatment with ethanol.