The effects of microinjection of d-amphetamine into the n. accumbens during the late maintenance phase of an ethanol consumption bout

The microinjection of d-amphetamine into the n. accumbens of rats, prior to the start of an operant ethanol self-administration session, increases ope rant behavior and the amounts of ethanol presented as the reinforcer. Altho ugh this effect could result by blocking termination processes regulating a consummatory bout, it could also be a result of enhancing the stimulus con trol regulating the maintenance of a drinking bout. To explore this issue, rats were trained to self-administer 10% ethanol in an operant situation. F ollowing establishment of stable behavior, they were surgically instrumente d so that the n. accumbens could be microinjected with d-amphetamine during a drinking bout, without having to handle the animal. The microinjection o f d-amphetamine in the rats self-administering ethanol at the late phase of the drinking bout resulted in a prolonged bout and increased self-administ ration During extinction testing, a reinstatement of responding was found f ollowing the amphetamine microinjection. The data suggest the most likely a ction of the amphetamine microinjection was to alter stimulus control facto rs, which normally regulate the maintenance of drinking, thereby prolonging the bout and increasing intake. (C) 1999 Elsevier Science Inc.