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

BACKGROUND

Binge drinking can increase an individual's risk of developing alcohol use disorder (AUD). Ethanol 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 αβ nAChR being a commonly expressed subtype. Desformylflustrabromine (dFBr), a positive allosteric modulator (PAM), increases the efficacy of αβ nAChR in vitro and has previously been shown to have translational potential. In this study, we investigated whether dFBr modulates the hypnotic response to ethanol.

METHODS

Ethanol-induced loss of righting reflex (LORR) duration was measured in the presence and absence of dFBr. The β nAChR selective antagonist dihydro-β-erythroidine (DHβE) was used to study the involvement of the β subunit. Additionally, we used a crosslinking-based western blot assay to estimate changes in total versus intracellular α nAChR protein in thalamic tissue of rats treated with vehicle, dFBr, ethanol, or ethanol and dFBr. Lastly, using Xenopus oocyte two-electrode voltage clamp (TEVC) studies, we determined the effects of ethanol and dFBr on αβ nAChR.

RESULTS

Pretreatment with 6 mg/kg dFBr reduced ethanol-induced LORR duration as compared to rats treated with ethanol alone. LORR studies with DHβE suggest that dFBr reduced ethanol-induced LORR duration via the β nAChR subunit. Crosslinking-based western analyses revealed that ethanol caused early increases in total and presumably surface thalamic α nAChR subunit protein levels. This ethanol-induced α nAChR upregulation was significantly reduced in rats pretreated with 6 mg/kg dFBr. In TEVC studies, ethanol potentiated ACh-induced currents in αβ nAChR, while it slightly reduced dFBr potentiation of maximal ACh currents.

CONCLUSIONS

Our results suggest that thalamic nAChRs containing the α subunit are rapidly upregulated by a single intoxicating dose of ethanol. Furthermore, dFBr, an αβ nAChR-selective PAM, significantly attenuates the hypnotic response to ethanol via actions on β nAChR. Overall, these results indicate that dFBr represents an option to reverse ethanol intoxication.