Effects of challenge injections on horizontal crossovers (A) and rearing (B) in non-anesthetized rats (i.e., all NoA groups) with histories of repeated cocaine or saline treatments. Rats received repeated daily treatments of either cocaine (C; 2 mg/kg, i.v.) or saline (S), followed by a challenge injection of C or S, with group names representing these sequential treatments. Values are presented as mean ± SEM. * p < 0.05 different from SS-NoA (Newman-Keuls). + p < 0.05 different from SC-NoA. Group sizes are CC-NoA: n=9, SC-NoA: n=6, SS-NoA: n=5.