Fig. 4
Cocaine-induced locomotor activity of rats exposed to nandrolone during postnatal days 28–37. Cocaine-induced locomotor activity of prepubertal rats injected daily from PN 28–37 with nandrolone (20 mg/kg) or sesame oil and tested for behavioral sensitization to cocaine from PN 40–62. A and B Timecourse of locomotor activity of saline (A) and nandrolone (B) treated males. No differences between oil and nandrolone-treated males were observed. C. A significant increase in cocaine-induced locomotor activity was observed when comparing the timecourses of day 40 vs. day 52 and day 40 vs. day 62 in Oil-treated males. Thus, these males displayed behavioral sensitization by day 52. D. A significant increase in cocaine-induced locomotor activity was observed when comparing the timecourses of day 40 vs. day 44 vs. day 52 and day 62 in nandrolone-treated males. These results suggest that nandrolone accelerates the maturation of the neural circuitry that regulates behavioral sensitization. Data are presented as mean ± SEM and analyzed with Repeated Measures ANOVA using Tukey’s multiple comparison for post-hoc analysis. E. Rats that received nandrolone show a robust increase in cocaine-induced locomotor activity by day 44, an increase that is maintained after two withdrawal periods. In contrast, it is at day 52 that oil-treated rats show a difference that is further increased by day 62. Data are presented as mean ± SEM (n = 10). Repeated Measures Two-Way ANOVA: F(3,27) = 4.173, p = 0.0150. Oil-Coc: Day 40 vs. Day 44, p = 0.9968; Day 40 vs. Day 52, p = 0.0288; Day 40 vs. Day 62, p = 0.0001. ND-Coc: Day 40 vs. Day 44, p = 0.0011; Day 40 vs. Day 52, p = < 0.0001; Day 40 vs. Day 62, p = 0.0002. Oil-Coc vs. ND- Coc: Day 40, p = 0.8684; Day 44, p = 0.0002; Day 52, p = 0.0230; Day 62 p = 0.9209. P < 0.05 was considered statistically significant on Day 40 vs. Day 44, Day 52, and Day 62. (*): significantly different within groups; (#): significantly different between groups (Oil-Cocaine vs. Nandrolone-Cocaine).
