Altered excitatory transmission in striatal neurons after chronic ethanol consumption in selectively bred crossed high alcohol-preferring mice

Dorsomedial striatal AMPA receptor antagonism increases alcohol binge drinking in selectively bred crossed high alcohol preferring mice

Crossed high alcohol preferring (cHAP) mice have been selectively bred to consume considerable amounts of alcohol resulting in binge drinking. The dorsomedial striatum (DMS) is a brain region involved in goal-directed action selection, and dorsolateral striatum (DLS) is a brain region involved in habitual action selection. Alcohol use disorder (AUD) may involve a disruption in the balance between the DMS and DLS. While the DLS is involved in binge drinking, the reliance on the DMS and DLS in binge drinking has not been investigated in cHAP mice. We have previously demonstrated that glutamatergic activity in the DLS is necessary for binge-like alcohol drinking in C57BL/6J mice, another high drinking mouse. Because of this, we hypothesised that DLS glutamatergic activity would gate binge-like alcohol drinking in cHAP mice. cHAP mice underwent bilateral cannulation into the DMS or DLS and were allowed free-access to 20% alcohol for 2 h each day for 11 days. Mice were microinjected with the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antagonist, NBQX, into the DMS or DLS immediately prior to alcohol access. AMPAR protein expression was also assessed in a separate group of animals in the DMS and DLS following an 11-day drinking history. We found that intra-DMS (but not intra-DLS) NBQX alters binge alcohol drinking, with intra-DMS NBQX increasing alcohol consumption. We also found that the ratio of GluA1 to GluA2 differs across dorsal striatal subregions. Together, these findings suggest that glutamatergic activity in the DMS may serve to limit binge drinking in cHAP mice.

Daily oscillations of neuronal membrane capacitance

Capacitance of biological membranes is determined by the properties of the lipid portion of the membrane as well as the morphological features of a cell. In neurons, membrane capacitance is a determining factor of synaptic integration, action potential propagation speed, and firing frequency due to its direct effect on the membrane time constant. Besides slow changes associated with increased morphological complexity during postnatal maturation, neuronal membrane capacitance is considered a stable, non-regulated, and constant magnitude. Here we report that, in two excitatory neuronal cell types, pyramidal cells of the mouse primary visual cortex and granule cells of the hippocampus, the membrane capacitance significantly changes between the start and the end of a daily light-dark cycle. The changes are large, nearly 2-fold in magnitude in pyramidal cells, but are not observed in cortical parvalbumin-expressing inhibitory interneurons. Consistent with daily capacitance fluctuations, the time window for synaptic integration also changes in pyramidal cells.

Ethanol's impact on the brain: a neurobiological perspective on the mechanisms of memory impairment

Alcohol consumption is known to have detrimental effects on memory function, with various studies implicating ethanol in the impairment of cognitive processes related to memory retention and retrieval. This review aims to elucidate the complex neurobiological mechanisms underlying ethanol-induced memory impairment. Through a thorough search of existing literature using electronic databases, relevant articles focusing on the neurobiological mechanisms of ethanol on memory were identified and critically evaluated. This review focuses on the molecular and neural pathways through which ethanol exerts its effects on memory formation, consolidation, and recall processes. Key findings from the included studies shed light on the impact of ethanol on neurotransmitter systems, synaptic plasticity, and neuroinflammation in relation to memory impairment. This review contributes to a better understanding of the intricate mechanisms by which alcohol impairs memory function, offering insights for future research directions and the development of targeted interventions to alleviate these cognitive impairments.

Home cage voluntary alcohol consumption increases binge drinking without affecting abstinence-related depressive-like behaviors or operant responding in crossed high alcohol-preferring mice (cHAPs)

Chronic alcohol consumption can lead to tolerance and escalation of drinking in humans and animals, but mechanisms underlying these changes are not fully characterized. Preclinical models can delineate which mechanisms are involved. The chronic intermittent ethanol exposure (CIE) procedure uses forced exposure to vaporized alcohol that elicits withdrawal and increased responding for alcohol in operant tasks in C57BL/6J inbred mice. Chronic two-bottle choice (2BC) drinking in the same strain elicits abstinent-related depression-like behavior, suggestive of allostatic changes. Selected lines such as crossed High Alcohol Preferring (cHAP) mice voluntarily drink to blood alcohol concentrations comparable to those attained in CIE and could be used to assess how alcohol affects these same endpoints without the confounds of involuntary vapor inhalation. In three experiments, we assess how 2BC drinking in cHAP mice affects abstinence-related depressive- and anxiety-like behavior, operant responding for alcohol, and binge consumption using drinking-in-the-dark (DID). We hypothesized that cHAPs with home-cage drinking experience would exhibit more depressive behavior after abstinence, increased responding for alcohol in the operant box, and increased DID intake. Of these, a drinking history increased DID intake in female cHAPs only and increased sucrose preference and intake following abstinence, but had no effects on operant responding or NSFT latency and FST immobility following forced abstinence. These results are consistent with recent findings using slice electrophysiology showing tolerance to alcohol's actions on the dorsolateral striatum following 2BC drinking in female, but not male cHAP mice. Overall, these data suggest that cHAPs may require procedures allowing rapid intoxication, such as DID, to demonstrate changes in alcohol's rewarding effects.

The role of anterior insular cortex inputs to dorsolateral striatum in binge alcohol drinking

How does binge drinking alcohol change synaptic function, and do these changes maintain binge consumption? The anterior insular cortex (AIC) and dorsolateral striatum (DLS) are brain regions implicated in alcohol use disorder. In male, but not female mice, we found that binge drinking alcohol produced glutamatergic synaptic adaptations selective to AIC inputs within the DLS. Photoexciting AIC→DLS circuitry in male mice during binge drinking decreased alcohol, but not water consumption and altered alcohol drinking mechanics. Further, drinking mechanics alone from drinking session data predicted alcohol-related circuit changes. AIC→DLS manipulation did not alter operant, valence, or anxiety-related behaviors. These findings suggest that alcohol-mediated changes at AIC inputs govern behavioral sequences that maintain binge drinking and may serve as a circuit-based biomarker for the development of alcohol use disorder.

Chronic ethanol exposure during adolescence impairs simple spike activity of cerebellar Purkinje cells in vivo in mice

Cerebellar Purkinje cells (PCs) play critical roles in motor coordination and motor learning through their simple spike (SS) activity. Previous studies have shown that chronic ethanol exposure (CEE) in adolescents impairs learning, attention, and behavior, at least in part by impairing the activity of cerebellar PCs. In this study, we investigated the effect of CEE on the SS activity in urethane-anesthetized adolescent mice by in vivo electrophysiological recordings and pharmacological methods. Our results showed that the cerebellar PCs in CEE adolescent mice expressed a significant decrease in the frequency and an increase in the coefficient of variation (CV) of SS than control group. Blockade of ɤ-aminobutyric acid A (GABA_A) receptor did not change the frequency and CV of SS firing in control group but produced a significant increase in the frequency and a decrease in the CV of SS firing in CEE mice. The CEE-induced decrease in SS firing rate and increase in CV were abolished by application of an N-methyl-D-aspartate (NMDA) receptor blocker, D-APV, but not by anα-amino-3-hydroxy-5-methyl -4-isoxazolepropionic acid (AMPA) receptor antagonist, NBQX. Notably, the spontaneous spike rate of molecular layer interneurons (MLIs) in CEE mice was significantly higher than control group, which was also abolished by application of D-APV. These results indicate that adolescent CEE enhances the spontaneous spike firing rate of MLIs through activation of NMDA receptor, resulting in a depression in the SS activity of cerebellar PCs in vivo in mice.

Perinatal activation of ER and ER but not GPER-1 masculinizes female rat caudate-putamen medium spiny neuron electrophysiological properties

Exposure to steroid sex hormones such as 17β-estradiol (estradiol) during early life potentially permanently masculinize neuron electrophysiological phenotype. In rodents, one crucial component of this developmental process occurs in males, with estradiol aromatized in the brain from testes-sourced testosterone. However, it is unknown whether most neuron electrophysiological phenotypes are altered by this early masculinization process, including medium spiny neurons (MSNs) of the rat caudate-putamen. MSNs are the predominant and primary output neurons of the caudate-putamen and exhibit increased intrinsic excitability in females compared to males. Here, we hypothesize that since perinatal estradiol exposure occurs in males, then a comparable exposure in females to estradiol or its receptor agonists would be sufficient to induce masculinization. To test this hypothesis, we injected perinatal female rats with estradiol or its receptor agonists and then later assessed MSN electrophysiology. Female and male rats on postnatal day 0 and 1 were systemically injected with either vehicle, estradiol, the estrogen receptor (ER)α agonist PPT, the ERβ agonist DPN, or the G-protein-coupled receptor 1 (GPER-1) agonist G1. On postnatal days 19 ± 2, MSN electrophysiological properties were assessed using whole cell patch clamp recordings. Estradiol exposure abolished increased intrinsic excitability in female compared to male MSNs. Exposure to either an ERα or ERβ agonist masculinized female MSN evoked action potential firing rate properties, whereas exposure to an ERβ agonist masculinized female MSN inward rectification properties. Exposure to ER agonists minimally impacted male MSN electrophysiological properties. These findings indicate that perinatal estradiol exposure masculinizes MSN electrophysiological phenotype via activation of ERα and ERβ.NEW & NOTEWORTHY This study is the first to demonstrate that estradiol and estrogen receptor α and β stimulation during early development sexually differentiates the electrophysiological properties of caudate-putamen medium spiny neurons, the primary output neuron of the striatal regions. Overall, this evidence provides new insight into the neuroendocrine mechanism by which caudate-putamen neuron electrophysiology is sexually differentiated and demonstrates the powerful action of early hormone exposure upon individual neuron electrophysiology.