Individual differences in behavioral responses to novelty and amphetamine self-administration in male and female rats

Previous work has shown that individual differences in locomotor activity i n an inescapable novel environment can predict acquisition of amphetamine s elf-administration. The current study examined whether individual differenc es in approach to novelty in a free choice test could also predict amphetam ine self-administration. Further, the current study examined whether indivi dual differences in either free choice or inescapable novelty tests could p redict responding for a nondrug reinforcer (sucrose) in the presence and ab sence of amphetamine. Male and female rats were first tested for their resp onse to free choice novelty, (playground maze and novelty-induced place pre ference tests) and inescapable novelty. They were then tested for acquisiti on of sucrose-reinforced responding, am phetamine-induced changes in mainte nance of sucrose-reinforced responding, and amphetamine self-administration . Based on the inescapable novelty test, acquisition of sucrose-reinforced responding was more rapid in male high responders (HR) compared to low resp onders (LR). This effect in males did not generalize to females. None of th e novelty tests predicted the ability of amphetamine to decrease sucrose-ma intained responding. However, using the inescapable novelty test, both male and female HRs self-administered more amphetamine than LRs within the dose range tested (0.03-0.16 mg/kg/infusion). Neither the playground maze nor t he novelty-induced place preference test predicted amphetamine self-adminis tration. These results indicate that responses to free choice novelty and i nescapable novelty predict different components of amphetamine-induced beha vior. (C) 2001 Lippincott Williams & Wilkins.