NAC pretreatments (i.m.) did not significantly alter rates of responding under a fixed-interval avoidance schedule when saline was administered i.m. 5 sec prior to the session (A, 30 min ptx; C, 3h ptx). Furthermore, NAC pretreatments did not significantly alter amphetamine-induced increases in rates of responding when amphetamine (0.1 mg/kg) was administered i.m. 5 sec prior to the session (B, 30 min ptx; D, 3h ptx). Abscissae: time in minutes. Ordinates: rates of responding expressed as a percent of baseline control rates.