Increased Alcohol Consumption in Mice Lacking Sodium Bicarbonate Transporter NBCn1

Jesse R Schank,Lauren A Jeffers,Yejin Kim,Hannah D Fulenwider,Ebbe Boedtkjer,Inyeong Choi,Jianjun Chang,Jaegwon Chung,Jun Ming Li,Christian Aalkjaer,Sadie E Nennig,Soojung Lee,Jae-Kyung Lee,Carlos E Gonzalez-Islas,Zhe Jin

doi:10.1038/s41598-020-67291-0

Abstract

The previous reports on an addiction vulnerability marker in the human SLC4A7 gene encoding the Na/HCO3 transporter NBCn1 suggest that this pH-regulating protein may affect alcohol-related behavior and response. Here, we examined alcohol consumption and sensitivity to the sedative effects of alcohol in male NBCn1 knockout mice. These mice displayed lower pH in neurons than wildtype controls, determined by intracellular pH in hippocampal neuronal cultures. Neurons from knockout mice had a higher action potential threshold and a more depolarized membrane potential, thus reducing membrane excitability. In a two-bottle free choice procedure, knockout mice consumed more alcohol than controls and consistently increased alcohol consumption after repeated alcohol deprivation periods. Quinine and sucrose preference was similar between genotypes. Knockout mice showed increased propensity for alcohol-induced conditioned place preference. In loss of righting reflex assessment, knockout mice revealed increased sensitivity to alcohol-induced sedation and developed tolerance to the sedation after repeated alcohol administrations. Furthermore, chronic alcohol consumption caused NBCn1 downregulation in the hippocampus and striatum of mice and humans. These results demonstrate an important role of NBCn1 in regulation of alcohol consumption and sensitivity to alcohol-induced sedation.

Highlights

PH is a broad but important biological factor that can cause significant changes in brain function1,2. pH can change activities of numerous proteins such as neurotransmitter receptors, ion channels, and synaptic transmission machinery proteins, and such changes perturb membrane excitability, firing properties, and intracellular signaling cascades[3,4]
The decrease in dpH/dt corresponded to 76%, indicating that NBCn1 is the major HCO3−-dependent acid extruder in hippocampal neurons
These results indicate that NBCn1 loss leads to intracellular acidosis in neurons

Summary

Introduction

PH is a broad but important biological factor that can cause significant changes in brain function1,2. pH can change activities of numerous proteins such as neurotransmitter receptors, ion channels, and synaptic transmission machinery proteins, and such changes perturb membrane excitability, firing properties, and intracellular signaling cascades[3,4]. Genome-wide association studies discovered the single nucleotide polymorphism rs3278, in the human SLC4A7 gene, prevalent among abusers who used cannabinoid, cocaine, heroin, or nicotine in the US population[14] This polymorphism is prevalent in alcohol abusers in the Collaborative Studies on Genetics of Alcoholism pedigrees and in substance abusers who displayed the maximum www.nature.com/scientificreports possible 3+ on the drug use scale[15]. We reported that the genomic function of rs3278 is to enhance an alternative gene transcription for an N-terminally deleted protein that has a defect in membrane expression and alters pHi16. This finding suggests that abnormal function in NBCn1 is likely a physiological indicator of substance abuse or may directly affect addiction vulnerability. Given that a small pH difference has been considered minor in function, a marked change in alcohol-related behaviors by NBCn1 loss is intriguing

Methods

Results

Conclusion