Chronic intermittent amphetamine pretreatment enhances future appetitive behavior for drug- and natural-reward: interaction with environmental variables

Appetitive behavior for drug and sexual reward is enhanced in animals with a history of amphetamine-experience. The present experiment investigated whether prior exposure to a sensitizing regimen of amphetamine treatment would ‘globally’ enhance future appetitive behaviors of adult male Sprague-Dawley rats, and whether the drug preexposure-environment or intermittency of administration would affect this development. Reward appetite was compared in drug-experienced versus drug-naive rats using amphetamine place-preference conditioning (CPP) and a natural-incentive sensitization task, which measured appetitive approach for food and sexual reward. Experiment I found that 10 daily exposures to 1 mg/kg amphetamine did not alter future psychostimulant CPP, regardless of abstinence schedule. Although daily exposure to a higher amphetamine dose also did not alter appetitive behavior when measured after 2-weeks drug abstinence in Experiment II, alternate-day amphetamine experience (5.0 mg/kg, twice-a-day) in an initially unfamiliar environment persistently enhanced future amphetamine CPP and appetitive behavior for natural reward. Identical treatment administered in the homecage did not. Furthermore, sensitized reward-seeking behaviors were not globally evident. Animals that showed sensitized amphetamine CPP did not show sensitized food-seeking behavior and vice versa. Thus, the environment surrounding chronic psychostimulant drug experience can greatly affect subsequent reward appetite, but the sensitized expression may be individually determined.