Figure 3. Pinealectomy (Pnx) increases cocaine-induced locomotor activity. A) Experiment timeline. The zero time point corresponds to the basal locomotor activity (BLA). B) Mean (10 days) locomotor activity (± standard error of the mean [SEM]) by group (n=8 animals per group) at ZT4, ZT10, ZT16, and ZT22. White bars correspond to the administration of saline (SAL) and black bars correspond to the administration of cocaine (COC). C) Effect of pinealectomy on the mean concentration ± SEM of serum melatonin. *Significant (p < 0.01) effects of COC on locomotor activity compared to the SAL groups. ^† Significant (p < 0.01) effects of COC or SAL on locomotor activity at ZT4 compared to ZT10. ^‡ Significant (p < 0.01) effects of COC or SAL on locomotor activity at ZT16 compared to ZT22. ^§ Significant (p < 0.01) effects of COC or SAL on locomotor activity at ZT10 compared to ZT16. ^|| Significant (p < 0.01) effects of COC or SAL on locomotor activity at ZT22, compared to ZT4, determined by a three-way analysis of variance (ANOVA) followed by Tukey’s tests. ^¶ Significant (p < 0.01) effects induced by pinealectomy on serum melatonin levels at ZT22 determined by one-way ANOVA following Tukey’s tests.