Figure 5

Time-dependent and conditioned for place preference effects of cocaine exposure on miR-124 expression in the reward circuitry of mice brain. (A–I) Time-dependent effects of cocaine exposure on miR-124. Mice were injected with a single dose of cocaine (20 mg/kg) daily until Day 6. On the day 2, 4, and 6, mice were euthanized, NAc, PFC, and VTA were used for miRNA isolations. miR-124 expression was measured by qPCR and expressed as relative to the expression of 5 s rRNA levels. Relative expression of miR-124 in the respective tissue regions of cocaine-treated mice (n = 6) were compared to that of saline-treated mice (n = 6) for each time point. Effects of cocaine on miR-124 expression levels at day 2 (A); day 4 (B); and day 6 (C) in the NAc. Time-dependent effects of cocaine on miR-124 expression in the PFC at day 2 (D), day 4 (E), and day 6 (F). miR-124 expression levels in the VTA of mice brain at day 2 (G); day4 (H); and day 6 (I). Data in (A–I) are average normalized expression values from n = 6, per experimental group for each time point, conducted in triplicates with error bars representing ± SEM. (J, K) Cocaine-induced CPP of mice. (J) CPP scores were calculated as time spent by the animals (n = 12 for cocaine-treated group and n = 12 for saline-treated group) in the cocaine-paired chamber (20 mg/kg i.p.) minus time spent in the saline-paired chamber. On day 8, mice were euthanized, NAc tissue was used for miRNA isolations from cocaine and saline treated groups. miR-124 expression was measured by qPCR and expressed as relative to the expression of 5 s rRNA levels. K Expression of miR-124 of cocaine-treated mice (n = 9) were plotted relative to that of saline-treated mice (n = 9). Paired two-tailed t test was used to compare the pre-test vs. post-test independently within control and cocaine groups in panel J. CPP score for animals conditioned for cocaine (day8 post-test vs. day1 pre-test) whereas Unpaired two-tailed t test was employed to determine significance of difference in miR-124 levels between saline and cocaine treatments in Panel K. Data from the qPCR experiments are average normalized expression values from n = 9, per group, conducted in triplicates with error bars representing ± SEM. *represents p < 0.05, and ***p < 0.001 for statistical significance, whereas ns represents not significant.