Effect And Mechanism Of Cocaine Exposure On MiR-20b-3p In Rat Striatum

Objectives:mi RNA is a small RNA that can regulate the RNA shearing and the gene expression after transcription, resulting in the inhibition of protein expression. mi RNAs have been proved to play a role in cocaine addiction, thus in this part we studied the changes of mi RNA at different times after cocaine exposure in rats.Methods: Three various protocols of exposure to cocaine were performed including: a single cocaine exposue, chronic long-term exposure for 7 days and withdrawal after chronic long-term cocaine exposure. Then locomotor activity was tested after exposure to cocaine; After the injection of mi RNA mimic into the dorsal striatum, the expression of mi R-20b-3p was detected by RT-PCR, locomotor activity was tested after exposure to cocaine.Results : Bioinformatic method predicted the mi RNAs targets of munc18-1 include mi R-20b-3p?mi R-17-1-3p?mi R-3545-3p and mi R-3570.(1) 1 h after a single cocaine exposure, the mi R-20b-3p was significantly decreased in dorsal stritum(control: 1.12 ± 0.20; cocaine: 0.47 ± 0.13; n=5-6; P<0.05 vs control). After mimic injection, the expression of mi R-20b-3p was increased(control: 0.92 ± 0.12; mimic: 5.87 ± 2.06, n=5; P<0.05 vs control), and reversed the locomotor activity(control: 169.01 ± 36.48 m, n=4; mimic: 95.59 ± 15.10 m, n=8; P<0.05 vs control) after cocaine exposure.(2) After the long-term chronic exposure to cocaine, the expression of mi R-20b-3p was significantly decreasd in shell, not in dorsal stritum(control: 1.00 ± 0.12; cocaine: 0.06 ± 0.01; n=5-9; P<0.05 vs control).(3) After withdrawal from a chronic long-term cocaine exposure, the expression of mi R-20b-3p was significantly decreased in dorsal striatum, nucleus accumbens and amygdala(striatum, control: 1.00 ±0.24; cocaine: 0.31±0.04; NAc, control: 1.00±0.14; cocaine: 0.65±0.07; Amy, control: 1.00 ±0.22; cocaine: 0.46 ±0.06, n=5-10, P<0.05 vs control, but not in m PFC or hippocampus. The nucleus accumbens include shell and core, the expression of mi R-20b-3p was significantly decreased in shell(control: 1.00 ± 0.17; cocaine: 0.47 ± 0.09, n=5-6; P<0.01 vs control) but not in core(control: 1.00 ± 0.14; cocaine: 0.92 ± 0.12; n=6-10). In the dorsal striatum, the expression of mi R-17-1-3p, mi R-3545-3p and mi R-3570 was also decreased(mi R-17-1-3p, control: 1.00±0.13; cocaine: 0.54 ± 0.05; mi R-3545-3p, control: 1.00±0.18; cocaine: 0.34±0.07; mi R-3570, control: 1.00 ±0.06; cocaine: 0.43 ± 0.15, n=4-10, P<0.05 vs control). After mimic injection, the sugar preference rate was reversed(control: 23.70±5.92 %; mimic: 61.21± 13.13 %, n=6-7; P<0.05 vs control).Conclusion: The expression of mi R-20b-3p was significantly decreased after 1 h a single cocaine exposure, long-term chronic exposure and withdrawal after a chronic long-term cocaine exposure, after mimic injection, the munc18-1 and the locomotor activity was decreased and reverse the sugar preference rate.