Figure 1. Nicotine self-administration with CS₂ in adolescent rats.

Adolescent female Sprague-Dawley rats implanted with jugular catheters were placed in operant chambers equipped with two lickometers. Licking on the active spout that met a fixed-ratio 10 reinforcement schedule triggered contingent delivery of oral CS₂ (500 ppm, dissolved in water) and i.v. saline (a) or i.v. nicotine (b). No olfactogustatory cue was used. Both groups showed preference for the active spout. The average number of infusions (c) was 12.9±1.9 for rats that self-administered saline, and 6.7±0.4 for rats that self-administered nicotine. **: p<0.01; ***: p<0.001, repeated measures ANOVA.