Locomotor activity predicts acquisition of self-administration behavior but not cocaine intake

The current study investigates locomotor activity in a novel environment and correlates these activity levels with cocaine self-administration in rats that were either trained or untrained on a lever-pressing task prior to cocaine self-administration. The authors report that it is the rate of learning the lever-pressing task, not cocaine self-administration, that correlates with locomotor activity. The results suggest that a correlation between locomotor activity and cocaine self-administration is secondary to a link between locomotor activity and rate of learning to lever press for a reward. The authors conclude that locomotor activity is not necessarily an indicator of propensity to self-administer cocaine and demonstrate that environmental novelty and rate of learning an operant task are important considerations when designing experiments on drug-seeking behaviors.