Fig. 3.

LY354740 (4 mg/kg, i.p.) did not potentiate the reinforcement rate–increasing and response rate–decreasing effects of fluoxetine in rats (n = 8) performing under a DRL 72-s schedule. Rats were administered fluoxetine (2.5–10 mg/kg, i.p.) or vehicle 60 minutes prior to the hour-long behavioral session and were also injected with LY354740 or vehicle 30 minutes prior to the beginning of the 1-hour behavioral session. For the vehicle/vehicle condition, the mean (±S.D.) number of reinforcers obtained was 7.6 (±1.2), whereas the mean number of total responses was 88.4 (±5.0). For reinforcers obtained at the 10 mg/kg fluoxetine dose, both the fluoxetine alone condition and the fluoxetine/LY354740 condition were increased 2-fold from vehicle conditions, ***P < 0.001. For total responses obtained at the 10-mg/kg fluoxetine dose, both the fluoxetine alone condition and the fluoxetine/LY354740 condition were decreased from vehicle conditions by 30% and 18%, respectively, ***P < 0.001. F, fluoxetine; LY, LY354740; V, vehicle.