Knock‐in Mice Expressing an Ethanol‐Resistant GluN2A NMDA Receptor Subunit Show Altered Responses to Ethanol

Abstract

Background: N-methyl-D-aspartate receptors (NMDARs) are glutamate-activated, heterotetrameric ligand-gated ion channels critically important in virtually all aspects of glutamatergic signaling. Ethanol (EtOH) inhibition of NMDARs is thought to mediate specific actions of EtOH during acute and chronic exposure. Studies from our laboratory, and others, identified EtOH-sensitive sites within specific transmembrane (TM) domains involved in channel gating as well as those in subdomains of extracellular and intracellular regions of GluN1 and GluN2 subunits that affect channel function. In this study, we characterize for the first time the physiological and behavioral effects of EtOH on knockin mice expressing a GluN2A subunit that shows reduced sensitivity to EtOH.Methods: A battery of tests evaluating locomotion, anxiety, sedation, motor coordination, and voluntary alcohol intake were performed in wild-type mice and those expressing the GluN2A A825W knock-in mutation. Whole-cell patch-clamp electrophysiological recordings were used to confirm reduced EtOH sensitivity of NMDAR-mediated currents in 2 separate brain regions (mPFC and the cerebellum) where the GluN2A subunit is known to contribute to NMDAR-mediated responses.Results: Male and female mice homozygous for the GluN2A(A825W) knock-in mutation showed reduced EtOH inhibition of NMDAR-mediated synaptic currents in mPFC and cerebellar neurons as compared to their wild-type counterparts. GluN2A(A825W) male but not female mice were less sensitive to the sedative and motor-incoordinating effects of EtOH and showed a rightward shift in locomotor-stimulating effects of EtOH. There was no effect of the mutation on EtOH-induced anxiolysis or voluntary EtOH consumption in either male or female mice.Conclusions: These findings show that expression of EtOH-resistant GluN2A NMDARs results in selective and sex-specific changes in the behavioral sensitivity to EtOH.

Distinct Region- and Time-Dependent Functional Cortical Adaptations in C57BL/6J Mice after Short and Prolonged Alcohol Drinking

“…1B). Mice in this study did not increase their drinking across time (one week: F (1.983,25.78) = 0.9017, p = 0.417; four weeks: F (5.512,76.67) = 1.714, p = 0.1349; seven weeks: F (6.111,79.44) = 1.143, p = 0.3453), similar to that in some studies reporting no escalation of drinking when mice are given intermittent access to 20% ethanol starting on the first drinking session (Crabbe et al, 2012;Warnault et al, 2016;Rinker et al, 2017;Zamudio et al, 2020).…”

“…After acclimatization, mice were housed individually and were given 24-h IAA (20% v/v) and water from 9 A.M. to 9 A.M. with 24 or 48 h between drinking sessions (Mondays, Wednesdays, and Fridays;Rinker et al, 2017;Zamudio et al, 2020). Mice were subjected to the IAA model for 1 d, one week, four weeks, or seven weeks with three drinking sessions per week, and mice in the one-, four-, and seven-week groups began drinking on Wednesdays or Fridays.…”

Common and distinguishing genetic factors for substance use behavior and disorder: an integrated analysis of genomic and transcriptomic studies from both human and animal studies

“…It is well known that Ca 2+ are ubiquitous second messengers that can regulate membrane excitability and a variety of activities in eukaryotic cells, such as division, differentiation, proliferation, growth and apoptosis. These findings for the pathways and potential molecular mechanisms are consistent with previous studies [37, 38]. Hence, these four common genes may interact with each other to promote the development of SUBD by affecting neurotransmitter processes.…”

Chronic Ethanol Exposures Leads to a Negative Affective State in Female Rats That Is Accompanied by a Paradoxical Decrease in Ventral Hippocampus Excitability

“…This subunit is highly expressed in the CA1 region of the hippocampus (Paoletti, 2011). Polymorphisms in this subunit have also been implicated in human subjects with alcohol dependence lending clinical relevance to the multitude of studies in rodent models that have pointed to the importance of the GluN2A subunit in alcohol dependence (Boyce-Rustay and Holmes, 2006;Schumann et al, 2008;Domart et al, 2012;Daut et al, 2015;Jury et al, 2018;Zamudio et al, 2020). In conclusion, our findings, along with those of many other preclinical studies exploring the neurobiology of AUD and negative affective states, highlight important sex differences in both the behavioral consequences of chronic alcohol exposure and the neural circuitry that likely drives these maladaptive behaviors.…”