Desformylflustrabromine (dFBr), a positive allosteric modulator of the α4β2 nicotinic receptor modulates the hypnotic response to ethanol.

Abstract Background Binge drinking can increase an individual’s risk of developing alcohol use disorder (AUD). Ethanol (EtOH) targets multiple neurotransmitter systems, however, not much is known about its effects on the cholinergic system. Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels, the heteromeric α4β2 nAChR being a commonly expressed subtype. Desformylflustrabromine (dFBr), a positive allosteric modulator (PAM) increases the efficacy of α4β2 nAChR in vitro and has been shown to have translational potential previously. In this study, we investigated if dFBr modulates the hypnotic response to EtOH. Methods EtOH-induced loss of righting reflex (LORR) duration was measured in the presence and absence of dFBr. The β2 nAChR selective antagonist Dihydro-β-erythroidine (DHβE) was used to study the involvement of the β2 subunit. Additionally, we used a crosslinking-based western blot assay to estimate changes in total versus intracellular α4 nAChR protein in thalamic tissue of rats treated with vehicle, dFBr, EtOH, or EtOH and dFBr. Lastly, using Xenopus oocyte two-electrode voltage clamp (TEVC) studies, we determined the effects of EtOH and dFBr on α4β2 nAChR. Results Pretreatment with 6 mg/kg dFBr reduced EtOH-induced LORR duration as compared to rats treated with EtOH alone. LORR studies with DHβE suggest that dFBr reduced EtOH-induced LORR duration via the β2 nAChR subunit. Crosslinking-based western analyses revealed that EtOH caused early increases in total and presumably surface thalamic α4 nAChR subunit protein levels. This EtOH-induced α4 nAChR upregulation was significantly reduced in rats pretreated with 6 mg/kg dFBr. In TEVC studies, EtOH potentiated ACh-induced currents in α4β2 nAChR, while it slightly reduced dFBr potentiation of maximal ACh currents. Conclusions Our results suggest that thalamic nAChRs containing the α4 subunit are rapidly upregulated by a single intoxicating dose of EtOH. Furthermore, dFBr, a α4β2 nAChR-selective PAM significantly attenuates the hypnotic response to EtOH via actions on β2 nAChR. Overall, these results indicate that dFBr represents an option to reverse EtOH intoxication.