Figure 1.

Lever-press responses during self-administration training, extinction, and reinstatement sessions at the active (A) and inactive (B) lever. Training phase: Cocaine-reinforced responses during the final 3 days of the self-administration phase in rats (n = 15) trained to associate SΔs with the availability of intravenous cocaine (S⁺) vs. saline (S⁻). No differences were observed between responses during the first and second daily hour of cocaine availability, and responses for cocaine or saline between rats designated for testing under S⁺ vs. S⁻ conditions during the initial 3 days of the reinstatement phase (see Results). The data were, therefore, collapsed across groups and daily cocaine sessions for the purpose of this illustration. Extinction phase: Extinction responses at criterion. The extinction criterion (≤4 responses per session over three consecutive days) was reached within 16.4 ± 3.8 days (averaged across rats designated for testing under the S⁺ vs. S⁻ condition during the reinstatement phase). Reinstatement phase: Responses under the S⁺ (n = 7) and S⁻ (n = 8) reinstatement conditions. Exposure to the S⁺-elicited significant recovery of responding in the absence of further drug availability. Responding in the presence of the S⁻ remained at extinction levels. For statistical comparisons, see Results.