ABSTRACT
Chronic exposure to cocaine increases impulsive behavior, leading to a reduced preference for a larger, delayed reinforcer over a smaller, immediate reinforcer. This study examined the development of impulsivity over multiple days of cocaine exposure and cessation of cocaine. Male Sprague-Dawley rats were trained on a discrete-trials delay-discounting task, during which they chose between a small, immediate reinforcer of one food pellet and a large reinforcer of 3 food pellets after an adjusted delay (0, 10, 20, 40, and 60 s). When stable preferences were established, rats received daily injections of deionized water or cocaine (3, 7.5, 15 mg/kg) 5 min before the delay-discounting task for 9 days. All groups showed an increased preference for the smaller reinforcer as delay to the larger reinforcer increased. Repeated exposure to 7.5 or 15 mg/kg cocaine further decreased preference for the larger reinforcer over the 9 days. When cocaine administration was discontinued, preference for the larger reinforcer returned to baseline levels in the 7.5 mg/kg group, but remained depressed in the 15 mg/kg group. These findings indicate that continuing exposure to cocaine dose-dependently decreases choice for the large reinforcer over time, and that the bias remains when cocaine is no longer administered, and that the recovery after high doses of cocaine occurs slowly.
Subject(s)
Dopamine Uptake Inhibitors/pharmacology , Impulsive Behavior/chemically induced , Impulsive Behavior/psychology , Reinforcement, Psychology , Analysis of Variance , Animals , Choice Behavior/drug effects , Cocaine/administration & dosage , Conditioning, Operant/drug effects , Dopamine Uptake Inhibitors/administration & dosage , Dose-Response Relationship, Drug , Male , Rats , Rats, Sprague-Dawley , Reaction Time/drug effects , Reinforcement Schedule , Self Administration/methods , Time FactorsABSTRACT
The Minnesota Multiphasic Personality Inventory-Adolescent (MMPI-A) and Minnesota Multiphasic Personality Inventory-2 (MMPI-2) True Response Inconsistency (TRIN) scales are measures of acquiescence and non-acquiescence included among the standard validity scales on these instruments. The goals of this study were to evaluate the effectiveness of these scales in detecting varying degrees of acquiescence and non-acquiescence and to evaluate cutoff scores for clinical use. After the removal of invalid protocols from the MMPI-2 and MMPI-A normative samples, each normative sample was randomly divided in half. For each measure, one half of the normative sample served as a comparison group and the other half was modified with increasing degrees (10%, 20%, 30%, 40%, and 50%) of randomly inserted true or false responses. The results for a 9.1% base rate of acquiescence or non-acquiescence provide support for TRIN cutoff scores at or near those presented in the MMPI-A and MMPI-2 manuals.
