Sensory reinforcment as an animal model of sensation seeking: Strength of association to cocaine self-administration
Gancarz, Amy M.
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Rationale. Animal drug self-administration (SA) possesses both face and predictive validity and is widely used to model drug abuse in humans. In humans, many individuals experiment with drugs, but relatively few become drug abusers. Because of the observation of strong individual differences in drug addiction there has been increasing interest in identifying individual differences that predispose individuals toward uncontrolled drug abuse. A personality trait that predisposes individuals to drug use is Sensation Seeking, generally described as preference for novel sensations and experiences. Individuals who score high on Sensation Seeking scales have greater drug use compared to those who score low on these scales. In rodents, locomotor response to a novel environment (Loco) has been found to be predictive of drug SA and has been hypothesized to be an animal model of Sensation Seeking. In animal SA procedures, drug delivery is often paired with the onset of visual stimuli. Interestingly, a number of studies have demonstrated that animals will respond to produce visual stimuli alone. In previous research, we have found that Loco and responding to produce a visual reinforcer are related. The primary goal of this research is to evaluate the hypothesis that sensitivity to the reinforcing effects of a visual stimulus predicts acquisition of drug SA in rats and may be used as an animal model for Sensation Seeking. Goal. The goal of this research was to evaluate the relationships between Loco, light reinforced responding, and acquisition and maintenance of responding for cocaine and water reinforcers. Methods. Experiment 1 examined the association between Loco and light reinforced responding. Experiment 2 tested the ability of Loco and light reinforced responding to predict acquisition and maintenance of cocaine self-administration. Experiment 3 tested the ability of loco and light reinforced responding to predict acquisition and maintenance of a water reinforcer. Results. In Experiment 1, we found that Loco was positively associated with the rate of responding for a novel light reinforcer. In Experiment 2, it was determined that neither Loco nor Light reinforcement predicted acquisition of cocaine self-administration. However, there was some evidence that responding for a visual reinforcer predicted the rate of cocaine SA in animals that acquired the cocaine SA behavior. In Experiment 3, it was determined that both Loco and light reinforcement performance predicted the rate of water SA. Conclusions. The association found between Loco and light reinforcement indicates that these behaviors may be mediated by similar behavioral processes. The finding of no association between Loco and acquisition of cocaine self-administration was unexpected, as there is a large literature indicating the two are related. A second unexpected result was that Loco and light reinforced responding were predictive of the rate of responding for water. A number of factors that may have contributed to these discrepant results are discussed. One possibility supported by the data is that this relationship may be dependent on the use of visual or other sensory cues to signal drug delivery. Light reinforcement was a better predictor of both cocaine and water SA than Loco. These results provide some evidence for the use of light reinforcement as an animal model of Sensation Seeking. KEYWORDS: operant conditioning, sensory reinforcement, drug abuse, vulnerability, rat, psychomotor stimulants