Performance under a Go/No-go task in rats selected for high and low impulsivity with a delay-discounting procedure

Research with animals and humans suggests that impulsivity is both a determinant and a consequence of drug abuse. In the present study, rats screened for high (Hil) or low (Lol) impulsivity using a delay-discounting task were compared on a Go/No-go procedure for intravenous cocaine (0.4 mg/kg) or saccharin pellets (0.1%). An additional aim was to examine the effects of previous cocaine exposure on impulsive choice. Thus, following Go/No-go testing, Hil and Lol rats were reevaluated on delay discounting. The results indicated that Hil and Lol rats did not differ in Go (reinforced) responses or in the number of reinforcements earned under the cocaine or saccharin conditions. However, Lol rats made significantly more No-go (nonreinforced) responses under the cocaine versus the saccharin condition. After the Go/No-go procedure, cocaine-exposed Lol rats were more impulsive on the delay-discounting task for food, compared to Lol rats that were naive to cocaine; however, Hil rats did not differ on this measure. These results indicate that the effects of cocaine on measures of impulsivity may be determined by a preexisting level of impulsive behavior. Behavioural Pharmacology 20:406-414 (C) 2009 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.