Fig. 2.
Menthol dose-response function for enhancement of nicotine self-administration at 0.015 mg/kg/infusion. Five minutes prior to the test sessions, the rats (n = 11) received an intraperitoneal injection of menthol at different doses in a Latin-square design. During the sessions, the rats responded on the active lever for nicotine self-administration at 0.015 mg/kg/infusion on an FR5 schedule of reinforcement. The data are expressed as mean ± SEM. **p < 0.01, significant difference from vehicle treatment.