Figure 1.

Choice between saccharin and heroin or cocaine in the discrete choice setting. (a) Mean percent heroin (rats S/H, n=17) or cocaine (rats S/C, n=16) choices (±SEM) as a function of testing sessions. The horizontal dashed line at 50% represents the indifference level. The doses of heroin and cocaine per injection were 0.01 and 0.25 mg, respectively. Water was sweetened with 0.2% of saccharin. ^#Different from the indifference level (p<0.05, t-test). (b) Distribution of individual preference scores in rats S/H (n=17) and rats S/C (n=16). Individual preference scores were computed by averaging percent of drug choices over the last three choice sessions.