SL 327, an inhibitor of ERK activation, partially inhibits cocaine-induced hyperlocomotion. SL 327 (50 mg/kg, i.p.) was injected 1 hr before cocaine. A, Note the total inhibition of cocaine-induced P-ERK immunoreactivity by SL 327. B, Effect of SL 327 on cocaine-induced hyperlocomotion (n = 8 mice for each group). Statistical comparisons were performed as described Figure 2.