Impulsivity on a Go/No-go task for intravenous cocaine or food in male and female rats selectively bred for high and low saccharin intake

The purpose of this study was to examine a form of impulsive behavior (impaired inhibition) using cocaine or food reward in addiction-prone and addiction-resistant rats that were bred for high saccharin (HiS) or low saccharin (LoS) intake, respectively. A Go/No-go procedure was used to examine cocaine and food reinforcement (Go component) and the inhibition of responding during a subsequent period of nonreward (No-go component). Rats were initially trained to self-administer intravenous cocaine (0.4mg/kg) under an FR 1 schedule during daily Go/No-go sessions consisting of three components of cocaine reinforcement (Go) alternating with two nonreward components (No-go), each signaled by different stimuli. Responding and drug intake were compared under three FR values (FR 1, FR 3, and FR 5) and three cocaine doses (0.2, 0.4, and 0.8mg/kg). A similar Go/No-go procedure was used with food reinforcement and the same three FR conditions. During the Go components for intravenous cocaine, female rats self-administered more infusions at the 0.2 and 0.4mg/kg doses than males, indicating a sex difference in cocaine intake. During the No-go periods under the cocaine condition, HiS rats and females responded significantly more than LoS rats and males, indicating phenotype and sex differences in impaired inhibition. During the Go components with food reward, males responded more and earned more pellets than females, but there were no phenotype or sex differences in No-go responding (impulsivity). The results indicate that HiS rats and females are more prone than LoS rats and males to impulsive drug-seeking behavior.