Novelty seeking, incentive salience and acquisition of cocaine self-administration in the rat

Abstract

It has been suggested that incentive salience plays a major role in drug abuse and the development of addiction. Additionally, novelty seeking has been identified as a significant risk factor for drug abuse. However, how differences in the readiness to attribute incentive salience relate to novelty seeking and drug abuse vulnerability has not been explored. The present experiments examined how individual differences in incentive salience attribution relate to novelty seeking and acquisition of cocaine self-administration in a preclinical model. Rats were first assessed in an inescapable novelty task and a novelty place preference task (measures of novelty seeking), followed by a Pavlovian conditioned approach task for food (a measure of incentive salience attribution). Rats then were trained to self-administer cocaine (0.3 or 1.0 mg/kg/infusion) using an autoshaping procedure. The results demonstrate that animals that attributed incentive salience to a food-associated cue were higher novelty seekers and acquired cocaine self-administration more quickly at the lower dose. The results suggest that novelty-seeking behavior may be a mediator of incentive salience attribution and that incentive salience magnitude may be an indicator of drug reward.

Fig 1

A.) Relationship between sign tracking and goal tracking during conditioned Pavlovian approach. Data are expressed as the percentage of trials on which a sign tracking or goal tracking response occurred averaged over all 5 training sessions. B.) Sign tracking as a function of training session. C.) Goal tracking as a function of training session. Asterisk (*) represents significant difference from session 1 for sign tracking and session 5 for goal tracking at p < .05; n = 24.

Fig 2

A.) Relationship between locomotor activity in an inescapable novel environment and novelty place preference. B.) Relationship between sign tracking and locomotor activity in an inescapable novel environment. C.) Relationship between sign tracking and novelty preference. Locomotor activity is presented as the total distance traveled, measured in centimeters; novelty place preference is measured as the percentage of time spent in the novel environment during the novelty place preference task; sign tracking is presented as the percentage of trials on which a sign tracking response occurred; NS = not significant; n = 24.

Fig 3

Top panel: Relationship between sign tracking and cocaine infusions during acquisition of cocaine self-administration at a low dose (0.3 mg/kg/infusion). Sign tracking responses are presented as the percentage of trials on which a sign-tracking response occurred and cocaine infusions are expressed as the average number of infusions earned over the 7 days of FR1 acquisition. Bottom panel: Relationship between sign tracking responses and inactive lever presses during acquisition of cocaine self-administration at a low dose (0.3 mg/kg/infusion). Sign tracking responses are presented as the percentage of trials on which a sign tracking response occurred and inactive lever presses are expressed as the average number of responses emitted over the 7 days of FR1 acquisition. NS = not significant; n = 10.

Fig 4

Top panel: Relationship between sign tracking and cocaine infusions during acquisition of cocaine self-administration at a high dose (1.0 mg/kg/infusion). Sign tracking responses are presented as the percentage of trials on which a sign tracking response occurred and cocaine infusions are expressed as the average number of infusions earned over the 7 days of FR1 acquisition. Bottom panel: Relationship between sign tracking responses and inactive lever presses during acquisition of cocaine self-administration at a high dose (1.0 mg/kg/infusion). Sign tracking responses are presented as the percentage of trials on which a sign tracking response occurred and inactive lever presses are expressed as the average number of responses emitted over the 7 days of FR1 acquisition. NS = not significant; n = 11.