Ethanol interaction with alpha 3 beta 4 nicotinic acetylcholine receptors in neurons of the laterodorsal tegmentum

Background Nicotinic acetylcholine receptors (nAChRs) play a key role in the rewarding effects of ethanol (EtOH), and while several nAChR subtypes have been implicated, attention has recently shifted to a role for the alpha 3 beta 4 nAChR. The laterodorsal tegmental nucleus (LDTg), a brainstem cholinergic nucleus that sends excitatory projections to the ventral tegmental area, is an Integral part of the brain reward pathway. Here we investigate a potential role for LDTg alpha 3 beta 4 nAChRs in EtOH self-administration and reward. Methods Sprague-Dawley rats were given ad libitum access to a 20% EtOH solution, as part of a two-bottle choice paradigm. Approximately 1 week after removal of EtOH access, we measured LDTg alpha 3 beta 4 nAChR current responses to focal application of acetylcholine (ACh), using whole-cell patch clamp electrophysiology recordings in acute brain slices. In addition, we used whole-cell electrophysiology to assess the acute effects of EtOH on the sensitivity of LDTg alpha 3 beta 4 nAChRs. Results Focal application of ACh onto LDTg neurons resulted in large alpha 3 beta 4 nAChR-mediated inward currents, the magnitude of which showed a positive correlation with levels of EtOH self-administration. In addition, using brain slices taken from EtOH-naive rats, bath application of EtOH resulted in a moderate potentiation of LDTg alpha 3 beta 4 nAChR sensitivity. Conclusions Using a rat model, increased alpha 3 beta 4 nAChR function was associated with greater EtOH self-administration, with alpha 3 beta 4 nAChR function also acutely potentiated by EtOH. Assuming that similar findings apply to humans, the alpha 3 beta 4 nAChR could be a therapeutic target in the treatment of EtOH use disorder.