Abstract

BackgroundA number of studies have shown that ethanol (EtOH) activates dopamine neurocircuitries and is self-administered into the ventral tegmental area (VTA) of the rat brain. In vitro and in silico studies have showed that hyperpolarization-activated cyclic nucleotide-gated (HCN) ionic channels on VTA dopamine neurons may constitute a molecular target of EtOH; however, there is no in vivo evidence supporting this assumption. MethodsWistar-derived University of Chile Drinking (UChB) rats were microinjected into the VTA with a lentiviral vector coding for rat HCN-2 ionic channel or a control vector. Four days after vector administration, daily voluntary EtOH intake was assessed for 30days under a free-access paradigm to 5% EtOH and water. After EtOH consumption studies, the effect of HCN-2 overexpression was also assessed on EtOH-induced conditioned place preference (CPP); EtOH-induced locomotion, and EtOH-induced dopamine release in the nucleus accumbens (NAcc). ResultsRats microinjected with the HCN-2 coding vector into the VTA showed (i) a similar to 2-fold increase in their voluntary EtOH intake compared to control animals, (ii) lentiviral-HCN-2-treated animals also showed an increased CPP to EtOH (similar to 3-fold), (iii) a significant higher locomotor activity (similar to 2-fold), and (iv) increased dopamine release in NAcc upon systemic administration of EtOH (similar to 2-fold). ConclusionsOverexpression of HCN-2 ionic channel in the VTA of rats results in an increase in voluntary EtOH intake, EtOH-induced CPP, locomotor activity, and dopamine release in NAcc, suggesting that HCN levels in the VTA are relevant for the rewarding properties of EtOH.