Impulsivity predicts the escalation of cocaine self-administration in rats.
Impulsivity, as measured by the delay-discounting task, predicts the acquisition of cocaine self-administration and reinstatement of cocaine seeking in rats. The purpose of this study was to extend these results to the escalation phase of drug self-administration. Female rats were initially screened for high (HiI) or low (LoI) impulsivity for food reinforcement using a delay-discounting procedure. They were then implanted with i.v. catheters and trained to lever press for cocaine infusions (0.8 mg/kg). Once cocaine intake stabilized, rats were allowed to self-administer cocaine (0.4 mg/kg) under a fixed-ratio 1 (FR 1) schedule during three, 2 h short-access sessions. Subsequently, performance was briefly assessed under a progressive ratio (PR) schedule for 3 doses of cocaine (0.2, 0.8, and 3.2 mg/kg). Following PR testing, the cocaine dose was then changed to 0.4 mg/kg. Session length was then extended to 6 h for 21 days (extended access), and 0.4 mg/kg cocaine was available under a FR 1 schedule. After the 21-day extended access phase, responses and infusions under the short access FR and PR dose-response conditions were reassessed. The results indicated that HiI rats escalated cocaine-reinforced responding during the extended access condition, but LoI rats did not. HiI rats also earned significantly more infusions than LoI rats under the post-escalation short access FR condition. However, HiI and LoI rats did not differ under the pre- and post-extended access PR conditions. This study suggests that individual differences in impulsivity predict escalation of cocaine self-administration in female rats, which may have implications in the prediction of binge-like patterns of cocaine intake in women.
Anker
Justin J
JJ
Department of Psychiatry, University of Minnesota, Minneapolis, MN 55455, USA. anke0022@umn.edu
Perry
Jennifer L
JL
Gliddon
Luke A
LA
Carroll
Marilyn E
ME
D000818:Animals; D019970:Cocaine-Related Disorders / Q000523:psychology*; D003216:Conditioning, Operant / Q000187:drug effects; D003627:Data Interpretation, Statistical; D018450:Disease Progression; D005260:Female; D007175:Impulsive Behavior / Q000523:psychology*; D011379:Prognosis; D051381:Rats; D017208:Rats, Wistar; D012055:Reinforcement Schedule; D012646:Self Administration