Expression profile of nicotinic acetylcholine receptor subunits in the brain of HIV-1 transgenic rats given chronic nicotine treatment.

Abuse of addictive substances, including cigarettes, is much greater in HIV-1-infected individuals than in the general population and challenges the efficiency of highly active anti-retroviral therapy (HAART). The HIV-1 transgenic (HIV-1Tg) rat, an animal model used to study drug addiction in HIV-1-infected patients on HAART, displays abnormal neurobehavioral responses to addictive substances. Given that the cholinergic system plays an essential part in the central reward circuitry, we evaluated the expression profile of nine nicotinic acetylcholine receptor (nAChR) subunit genes in the central nervous system (CNS) of HIV-1Tg rats. We found that nAChR subunits were differentially expressed in various brain regions in HIV-1Tg rats compared to F344 control rats, with more subunits altered in the ventral tegmental area (VTA) and nucleus accumbens (NAc) of the HIV-1Tg rats than in other brain regions. We also found that chronic nicotine treatment (0.4 mg/kg/day) decreased the mRNA expression of nAChR subunits α6, β3, and β4 in the VTA of HIV-1Tg rats, whereas expression of α4 and α6 subunits in the NAc increased. No such changes were observed in F344 rats. Together, our data suggest that HIV-1 proteins alter the expression of nAChRs, which may contribute to the vulnerability to cigarette smoking addiction in HIV-1 patients.