Figure 1.
Data depict the mean number (±SEM) of responses during the first four extinction sessions (a) or the test for cocaine-induced reinstatement (b). Rats were assigned to self-administer cocaine under low- (0.5 mg/kg/200 μl, i.v.; 2 h/d) or high- (1.0 mg/kg/200 μl, i.v.; 6 h/d) intake conditions. Seven days after the last self-administration session, rats underwent daily extinction training in the absence of any drug treatment. This was followed by a test for cocaine-induced reinstatement (0, 5, 10, or 15 mg/kg, i.p.; for low-intake animals, N = 7, 5, 14, and 6, respectively; for high-intake animals, N = 8, 8, 9, and 7, respectively). *Significant difference from the 0 cocaine group (Fisher LSD, p < 0.0125). #Significant difference from the low-intake group receiving 10 mg/kg cocaine (t test, p < 0.0125).