Intense Sweetness Surpasses Cocaine Reward
a, the S-/C+ condition, or b, the S+/C+ condition. Locomotion (i.e., mean number of cage crossings±SEM) was measured during 10 min after the first cocaine self-injection (0.25 mg, i.v.) of the day (open triangle: day 1; closed circle: day 5; closed square: day 15). *, day 5 different from day 1; °, day 15 different from day 1 (P<0.05, Fisher's LSD test). c, Effects of the first cocaine self-injection in rats initially trained under the S+/C- condition and tested for the first time under the S+/C+ condition on day 16. These effects (open square) were compared to the effects of cocaine on day 15 in rats initially trained under the S+/C+ (closed square). *, P<0.05, Fisher's LSD test. The arrow in all graphs indicates the intravenous injection of cocaine.