Figure 3.

Intermittent-access (IntA) self-administration results in sensitization to the neurochemical effects of cocaine, while long-access (LgA) results in tolerance. (a) Representative traces highlighting the uptake inhibition induced by 10 μM cocaine in control (black) and short-access (ShA, green) animals. Traces are represented as concentration (μM) in dopamine (DA) over time and smaller signals were shifted to the right in order to match the peak-height of the small signal to equivalent concentration of the larger signal. This allows for direct comparison of dopamine uptake in signals with different peak-heights. (b) Representative traces highlighting the uptake inhibition induced by 10 μM cocaine in control (black), IntA (blue), and LgA (red) animals. (c) Cumulative cocaine (0.3–30 μM) dose–response curves in slices containing the nucleus accumbens core. Cocaine potency is decreased following LgA, unchanged following ShA, and increased following IntA. (d) Group data of K_i values for cocaine in control, LgA, ShA, and IntA groups. K_i values are a measure of the concentration of drug at which 50% inhibition is achieved. *P<0.5 vs control; **p<0.01 vs control; and ^#p<0.01 vs ShA.