Effects of nicotine exposure and ethanol-preferring behavior on mRNA expression of some nAChR subunits in the rat VTA

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Objective To investigate the effects of nicotine exposure and ethanol-preferring behavior on mRNA expression of some nAChR subunits in the rat ventral tegmental area(VTA) and to explore possible mechanisms of dependence on tobacco and alcohol.Methods 39 male Wistar rats,35-day-old,were randomly divided into an experimental group (group N,n=20) and a control group (group C,n=19).Rats in group N were treated with nicotine ( 1.0 mg · kg -1 · d -1 ) by subcutaneous injection while in group C with saline both for 10 days,after which 6 rats (respectively group NE,n =6,group CE,n =6 )were drawn randomly from each group and killed by cutting off the head.mRNA was extracted from the VTA tissue,and the expression of nAChR subunits,including α4,α5,α7 and β2,were examined by Real Time-PCR.Other rats both in groups N and C ( respectively group NA,n=14,group CA,n=13) were induced for 69 days to establish two-bottle free choice alcohol-preferring behavior model by Samson sucrose fading program from 60-day-old on.The same indexes mentioned above were detected by the same methods in the VTA tissue.Results ① The factor analysis showed that both the two factors,nicotine and alcohol-preferring behavior,showed regulating effects on the expression of nAChR subunits α4 and α5 ( respectively F was 6.13,5.407,5.186,7.132,P ＜ 0.05 ),and the factor,alcohol-preferring behavior,on subunit β2 (F =5.896,P＜0.05) ; the two factors exhibited strong interaction on the expression of subunit α7 (F=13.894,P＜0.001 ),and some interaction on subunits α5 and β2 (respectively F was 6.149,4.222,P＜0.05 ).② The mRNA expression of nAChR subunits α4,α5,α7,and β2 were significantly up-regulated by different degrees in group NA compared to group CA ( respectively Fwas 7.941,13.517,17.438,9.272,respectively P ＜ 0.05,P ＜ 0.05,P ＜ 0.01,P ＜ 0.01 ),the expression level of subunits α4,α5,α7 and β2 were significantly higher in different degrees in group NA than in group NE( respectively F was 5.293,8.500,6.149,4.837,P ＜0.05) ; while subunit α7 was significantly down-regulated in group CA compared to group CE (F =12.750,P ＜0.01 ).Conclusion Nicotine and ethanol co-affect on the nAChR subtype comprised of subunits α4,α5,α7 and β2. Key words: Nicotine exposure ; Alcohol dependence ; nAChR ; Ventral tegmental area ;