Fig. 4.

Nucleus accumbens dopamine concentrations in rats lever pressing during a 3 hr extinction period (no drug available) and a 2 hr reinstatement period (drug available). The arrow in each graph represents the time at which a rat received a noncontingent (priming) injection ofd-amphetamine and drug was made available again. Thehorizontal dotted line represents the baseline DA concentration. Dialysate samples were collected at 10 min intervals during the extinction period and at 5 min intervals during the reinstatement period. DL numbers are rat identification numbers.