Top, effects of cumulative doses of cocaine in separate groups of rats
treated with saline (saline), 0.3 mg/kg naltrexone (0.3 NTX), and 3.0 mg/kg
naltrexone (3.0 NTX). Bottom, effects of cumulative doses of cocaine in
separate groups of rats treated with saline (saline), 10 mg/kg
nor-binaltorphimine (10 NBNI), and 1.0 mg/kg naltrindole (1.0 NTI). Left,
locomotor activity expressed as a percentage of saline control values. Right,
AUC estimates for each group. Vertical lines, S.E.; where not indicated, the
S.E. fell within the data point.