Repeated ethanol withdrawal produces site-dependent increases in EEG spiking

Neuroimmune interactions with binge alcohol drinking in the cerebellum of IL-6 transgenic mice

The neuroimmune system of the brain, which is comprised primarily of astrocytes and microglia, regulates a variety of homeostatic mechanisms that underlie normal brain function. Numerous conditions, including alcohol consumption, can disrupt this regulatory process by altering brain levels of neuroimmune factors. Alcohol and neuroimmune factors, such as proinflammatory cytokines IL-6 and TNF-alpha, act at similar targets in the brain, including excitatory and inhibitory synaptic transmission. Thus, alcohol-induced production of IL-6 and/or TNF-alpha could be important contributing factors to the effects of alcohol on the brain. Recent studies indicate that IL-6 plays a role in alcohol drinking and the effects of alcohol on the brain activity following the cessation of alcohol consumption (post-alcohol period), however information on these topics is limited. Here we used homozygous and heterozygous female and male transgenic mice with increased astrocyte expression of IL-6 to examined further the interactions between alcohol and IL-6 with respect to voluntary alcohol drinking, brain activity during the post-alcohol period, IL-6 signal transduction, and expression of synaptic proteins. Wildtype littermates (WT) served as controls. The transgenic mice model brain neuroimmune status with respect to IL-6 in subjects with a history of persistent alcohol use. Results showed a genotype dependent reduction in voluntary alcohol consumption in the Drinking in the Dark protocol and in frequency-dependent relationships between brain activity in EEG recordings during the post-alcohol period and alcohol consumption. IL-6, TNF-alpha, IL-6 signal transduction partners pSTAT3 and c/EBP beta, and synaptic proteins were shown to play a role in these genotypic effects.

Alcohol withdrawal produces changes in excitability, population discharge probability, and seizure threshold

BACKGROUND

Alcohol withdrawal syndrome (AWS) results from the sudden cessation of chronic alcohol use and is associated with high morbidity and mortality. Alcohol withdrawal-induced central nervous system (CNS) hyperexcitability results from complex, compensatory changes in synaptic efficacy and intrinsic excitability. These changes in excitability counteract the depressing effects of chronic ethanol on neural transmission and underlie symptoms of AWS, which range from mild anxiety to seizures and death. The development of targeted pharmacotherapies for treating AWS has been slow, due in part to the lack of available animal models that capture the key features of human AWS. Using a unique optogenetic method of probing network excitability, we examined electrophysiologic correlates of hyperexcitability sensitive to early changes in CNS excitability. This method is sensitive to pharmacologic treatments that reduce excitability and may represent a platform for AWS drug development.

METHODS

We applied a newly developed method, the optogenetic population discharge threshold (oPDT), which uses light intensity response curves to measure network excitability in chronically implanted mice. Excitability was tracked using the oPDT before, during, and after the chronic intermittent exposure (CIE) model of alcohol withdrawal (WD).

RESULTS

Alcohol withdrawal produced a dose-dependent leftward shift in the oPDT curve (denoting increased excitability), which was detectable in as few as three exposure cycles. This shift in excitability mirrored an increase in the number of spontaneous interictal spikes during withdrawal. In addition, Withdrawal lowered seizure thresholds and increased seizure severity in optogenetically kindled mice.

CONCLUSION

We demonstrate that the oPDT provides a sensitive measure of alcohol withdrawal-induced hyperexcitability. The ability to actively probe the progression of excitability without eliciting potentially confounding seizures promises to be a useful tool in the preclinical development of next-generation pharmacotherapies for AWS.

Alcohol Withdrawal and the Associated Mood Disorders-A Review

Recreational use of alcohol is a social norm in many communities worldwide. Alcohol use in moderation brings pleasure and may protect the cardiovascular system. However, excessive alcohol consumption or alcohol abuse are detrimental to one's health. Three million deaths due to excessive alcohol consumption were reported by the World Health Organization. Emerging evidence also revealed the danger of moderate consumption, which includes the increased risk to cancer. Alcohol abuse and periods of withdrawal have been linked to depression and anxiety. Here, we present the effects of alcohol consumption (acute and chronic) on important brain structures-the frontal lobe, the temporal lobe, the limbic system, and the cerebellum. Apart from this, we also present the link between alcohol abuse and withdrawal and mood disorders in this review, thus drawing a link to oxidative stress. In addition, we also discuss the positive impacts of some pharmacotherapies used. Due to the ever-rising demands of life, the cycle between alcohol abuse, withdrawal, and mood disorders may be a never-ending cycle of destruction. Hence, through this review, we hope that we can emphasise the importance and urgency of managing this issue with the appropriate approaches.

Effects of Multiple Detoxifications on Withdrawal Symptoms, Psychiatric Distress and Alcohol-Craving in Patients with an Alcohol Use Disorder

Previous studies have shown an association between the number of withdrawal attempts and increased severity of withdrawal symptoms in patients with an alcohol use disorder (AUD). An underlying allostatic neuroadaptive response may negatively affect the withdrawal pathology after alcohol discontinuation. The objective of the present research is to examine the intensification of psychiatric distress, craving, and post-detoxification drinking outcomes, which may result from these neurobehavioral alternations. Fifty-two AUD inpatients were divided into two groups: <2 previous detoxifications and ≥2 previous detoxifications. Patients completed the Dutch version of the Severity of Withdrawal Scale (SWS), Depression Anxiety Stress Scales (DASS-21), VAS Craving, and Desires for Alcohol Questionnaire (DAQ). Linear mixed effects models were applied, controlling for the number of drinks consumed in the past 30 days and alcohol drinking history (years). Patients who had undergone ≥2 detoxifications reported statistically significantly higher scores on SWS withdrawal and DASS psychiatric symptoms. Also, craving patterns were different between groups, as shown by a statistically significant interaction effect for VAS craving for the time of day factor (morning vs. evening). No statistically significant group differences were found for DAQ scores and post-detoxification drinking outcomes. Due to relatively low 1-month follow-up rates our power was limited to detect such a difference. The present study contributes to the existing body of evidence that multiple detoxifications are associated with aggravated withdrawal/psychiatric pathology, and distinct diurnal patterns of VAS craving. Several clinical implications are discussed and alternative strategies are provided to manage repeated cycles of detoxifications.

Increased IL-6 expression in astrocytes is associated with emotionality, alterations in central amygdala GABAergic transmission, and excitability during alcohol withdrawal

Accumulating evidence from preclinical and clinical studies has implicated a role for the cytokine IL-6 in a variety of CNS diseases including anxiety-like and depressive-like behaviors, as well as alcohol use disorder. Here we use homozygous and heterozygous transgenic mice expressing elevated levels of IL-6 in the CNS due to increased astrocyte expression and non-transgenic littermates to examine a role for astrocyte-produced IL-6 in emotionality (response to novelty, anxiety-like, and depressive-like behaviors). Our results from homozygous IL-6 mice in a variety of behavioral tests (light/dark transfer, open field, digging, tail suspension, and forced swim tests) support a role for IL-6 in stress-coping behaviors. Ex vivo electrophysiological studies of neuronal excitability and inhibitory GABAergic synaptic transmission in the central nucleus of the amygdala (CeA) of the homozygous transgenic mice revealed increased inhibitory GABAergic signaling and increased excitability of CeA neurons, suggesting a role for astrocyte produced IL-6 in the amygdala in exploratory drive and depressive-like behavior. Furthermore, studies in the hippocampus of activation/expression of proteins associated with IL-6 signal transduction and inhibitory GABAergic mechanisms support a role for astrocyte produced IL-6 in depressive-like behaviors. Our studies indicate a complex and dose-dependent relationship between IL-6 and behavior and implicate IL-6 induced neuroadaptive changes in neuronal excitability and the inhibitory GABAergic system as important contributors to altered behavior associated with IL-6 expression in the CNS.

Activity of hippocampal adult-born neurons regulates alcohol withdrawal seizures

Alcohol withdrawal (AW) after chronic alcohol exposure produces a series of symptoms, with AW-associated seizures being among the most serious and dangerous. However, the mechanism underlying AW seizures has yet to be established. In our mouse model, a sudden AW produced 2 waves of seizures: the first wave includes a surge of multiple seizures that occurs within hours to days of AW, and the second wave consists of sustained expression of epileptiform spikes and wave discharges (SWDs) during a protracted period of abstinence. We revealed that the structural and functional adaptations in newborn dentate granule cells (DGCs) in the hippocampus underlie the second wave of seizures but not the first wave. While the general morphology of newborn DGCs remained unchanged, AW increased the dendritic spine density of newborn DGCs, suggesting that AW induced synaptic connectivity of newborn DGCs with excitatory afferent neurons and enhanced excitability of newborn DGCs. Indeed, specific activation and suppression of newborn DGCs by the chemogenetic DREADD method increased and decreased the expression of epileptiform SWDs, respectively, during abstinence. Thus, our study unveiled that the pathological plasticity of hippocampal newborn DGCs underlies AW seizures during a protracted period of abstinence, providing critical insight into hippocampal neural circuits as a foundation to understand and treat AW seizures.

Baclofen-induced encephalopathy in overdose - Modeling of the electroencephalographic effect/concentration relationships and contribution of tolerance in the rat

Baclofen, a γ-amino-butyric acid type-B receptor agonist with exponentially increased use at high-dose to facilitate abstinence in chronic alcoholics, is responsible for increasing poisonings. Baclofen overdose may induce severe encephalopathy and electroencephalographic (EEG) abnormalities. Whether prior prolonged baclofen treatment may influence the severity of baclofen-induced encephalopathy in overdose has not been established. We designed a rat study to characterize baclofen-induced encephalopathy, correlate its severity with plasma concentrations and investigate the contribution of tolerance. Baclofen-induced encephalopathy was assessed using continuous EEG and scored based on a ten-grade scale. Following the administration by gavage of 116 mg/kg baclofen, EEG rapidly and steadily impaired resulting in the successive onset of deepening sleep followed by generalized periodic epileptiform discharges and burst-suppressions. Thereafter, encephalopathy progressively recovered following similar phases in reverse. Periodic triphasic sharp waves, non-convulsive status epilepticus and even isoelectric signals were observed at the most critical stages. Prior repeated baclofen administration resulted in reduced severity (peak: grade 7 versus 9; peak effect length: 382 ± 40 versus 123 ± 14 min, P = 0.008) and duration of encephalopathy (18 versus > 24 h, P = 0.0007), supporting the acquisition of tolerance. The relationship between encephalopathy severity and plasma baclofen concentrations fitted a sigmoidal Emax model with an anticlockwise hysteresis loop suggesting a hypothetical biophase site of action. The baclofen concentration producing a response equivalent to 50% of Emax was significantly reduced (8947 μg/L, ±11.3% versus 12,728 μg/L, ±24.0% [mean, coefficient of variation], P = 0.03) with prior prolonged baclofen administration. In conclusion, baclofen overdose induces early-onset and prolonged marked encephalopathy that is significantly attenuated by prior repeated baclofen treatment. Our findings suggest a possible role for the blood-brain barrier in the development of tolerance; however, its definitive involvement remains to be demonstrated.

Altered brain activity during withdrawal from chronic alcohol is associated with changes in IL-6 signal transduction and GABAergic mechanisms in transgenic mice with increased astrocyte expression of IL-6

Interleukin-6 (IL-6) is an important neuroimmune factor that is increased in the brain by alcohol exposure/withdrawal and is thought to play a role in the actions of alcohol on the brain. To gain insight into IL-6/alcohol/withdrawal interactions and how these interactions affect the brain, we are studying the effects of chronic binge alcohol exposure on transgenic mice that express elevated levels of IL-6 in the brain due to increased astrocyte expression (IL-6 tg) and their non-transgenic (non-tg) littermate controls. IL-6/alcohol/withdrawal interactions were identified by genotypic differences in spontaneous brain activity in electroencephalogram (EEG) recordings from the mice, and by Western blot analysis of protein activation or expression in hippocampus obtained from the mice after the final alcohol withdrawal period. Results from EEG studies showed frequency dependent genotypic differences in brain activity during withdrawal. For EEG frequencies that were affected by alcohol exposure/withdrawal in both genotypes, the nature of the effect was similar, but differed across withdrawal cycles. Differences between IL-6 tg and non-tg mice were also observed in Western blot studies of the activated form of STAT3 (phosphoSTAT3), a signal transduction partner of IL-6, and subunits of GABA_A receptors (GABA_AR). Regression analysis revealed that pSTAT3 played a more prominent role during withdrawal in the IL-6 tg mice than in the non-tg mice, and that the role of GABA_AR alpha-5 and GABA_AR alpha-1 in brain activity varied across genotype and withdrawal. Taken together, our results suggest that IL-6 can significantly impact mechanisms involved in alcohol withdrawal.

Role of GABAA receptors in alcohol use disorders suggested by chronic intermittent ethanol (CIE) rodent model

GABAergic inhibitory transmission is involved in the acute and chronic effects of ethanol on the brain and behavior. One-dose ethanol exposure induces transient plastic changes in GABAA receptor subunit levels, composition, and regional and subcellular localization. Rapid down-regulation of early responder δ subunit-containing GABAA receptor subtypes mediating ethanol-sensitive tonic inhibitory currents in critical neuronal circuits corresponds to rapid tolerance to ethanol's behavioral responses. Slightly slower, α1 subunit-containing GABAA receptor subtypes mediating ethanol-insensitive synaptic inhibition are down-regulated, corresponding to tolerance to additional ethanol behaviors plus cross-tolerance to other GABAergic drugs including benzodiazepines, anesthetics, and neurosteroids, especially sedative-hypnotic effects. Compensatory up-regulation of synaptically localized α4 and α2 subunit-containing GABAA receptor subtypes, mediating ethanol-sensitive synaptic inhibitory currents follow, but exhibit altered physio-pharmacology, seizure susceptibility, hyperexcitability, anxiety, and tolerance to GABAergic positive allosteric modulators, corresponding to heightened alcohol withdrawal syndrome. All these changes (behavioral, physiological, and biochemical) induced by ethanol administration are transient and return to normal in a few days. After chronic intermittent ethanol (CIE) treatment the same changes are observed but they become persistent after 30 or more doses, lasting for at least 120 days in the rat, and probably for life. We conclude that the ethanol-induced changes in GABAA receptors represent aberrant plasticity contributing critically to ethanol dependence and increased voluntary consumption. We suggest that the craving, drug-seeking, and increased consumption in the rat model are tied to ethanol-induced plastic changes in GABAA receptors, importantly the development of ethanol-sensitive synaptic GABAA receptor-mediating inhibitory currents that participate in maintained positive reward actions of ethanol on critical neuronal circuits. These probably disinhibit nerve endings of inhibitory GABAergic neurons on dopamine reward circuit cells, and limbic system circuits mediating anxiolysis in hippocampus and amygdala. We further suggest that the GABAA receptors contributing to alcohol dependence in the rat and presumably in human alcohol use disorders (AUD) are the ethanol-induced up-regulated subtypes containing α4 and most importantly α2 subunits. These mediate critical aspects of the positive reinforcement of ethanol in the dependent chronic user while alleviating heightened withdrawal symptoms experienced whenever ethanol is absent. The speculative conclusions based on firm observations are readily testable.

Ethanol withdrawal-induced dysregulation of neurosteroid levels in plasma, cortex, and hippocampus in genetic animal models of high and low withdrawal

RATIONALE

Endogenous γ-aminobutyric acidA receptor (GABAAR)-active neurosteroids (e.g., allopregnanolone) regulate central nervous system excitability and many physiological functions, so fluctuations are implicated in several neuropsychiatric disorders. Pertinently, evidence supports an inverse relationship between endogenous GABAAR-active neurosteroid levels and behavioral changes in excitability during ethanol withdrawal (WD).

OBJECTIVES

The present studies determined mouse genotype differences in ten neurosteroid levels in plasma, cortex, and hippocampus over the time course of ethanol WD in the WD Seizure-Prone (WSP) and WD Seizure-Resistant (WSR) selected lines and in the DBA/2J (DBA) inbred strain.

METHODS

Gas chromatography-mass spectrometry was utilized to simultaneously quantify neurosteroid levels from control-treated male WSP-1, WSR-1, and DBA mice and during 8 and 48 h of WD.

RESULTS

Combined with our prior work, there was a consistent decrease in plasma allopregnanolone levels at 8 h WD in all three genotypes, an effect that persisted at 48 h WD only in DBA mice. WSR-1 and WSP-1 mice exhibited unexpected divergent changes in cortical neurosteroids at 8 h WD, with the majority of neurosteroids (including allopregnanolone) being significantly decreased in WSR-1 mice, but unaffected or significantly increased in WSP-1 mice. In DBA mice, hippocampal allopregnanolone and tetrahydrodeoxycorticosterone were significantly decreased at 8 h WD. The pattern of significant correlations between allopregnanolone and other GABAAR-active neurosteroid levels differed between controls and withdrawing mice.

CONCLUSIONS

Ethanol WD dysregulated neurosteroid synthesis. Results in WSP-1 mice suggest that diminished GABAAR function is more important for their high WD phenotype than fluctuations in neurosteroid levels.

Ethanol withdrawal is required to produce persisting N-methyl-D-aspartate receptor-dependent hippocampal cytotoxicity during chronic intermittent ethanol exposure

Chronic intermittent ethanol consumption is associated with neurodegeneration and cognitive deficits in preclinical laboratory animals and in the clinical population. While previous work suggests a role for neuroadaptations in the N-methyl-D-aspartate (NMDA) receptor in the development of ethanol dependence and manifestation of withdrawal, the relative roles of ethanol exposure and ethanol withdrawal in producing these effects have not been fully characterized. To examine underlying cytotoxic mechanisms associated with CIE exposure, organotypic hippocampal slices were exposed to 1–3 cycles of ethanol (50 mM) in cell culture medium for 5 days, followed by 24-hours of ethanol withdrawal in which a portion of slices were exposed to competitive NMDA receptor antagonist (2R)-amino-5-phosphonovaleric acid (APV; 40 µM). Cytotoxicity was assessed using immunohistochemical labeling of neuron specific nuclear protein (NeuN; Fox-3), a marker of mature neurons, and thionine (2%) staining of Nissl bodies. Multiple cycles of CIE produced neurotoxicity, as reflected in persisting losses of neuron NeuN immunoreactivity and thionine staining in each of the primary cell layers of the hippocampal formation. Hippocampi aged in vitro were significantly more sensitive to the toxic effects of multiple CIEs than were non-aged hippocampi. This effect was not demonstrated in slices exposed to continuous ethanol, in the absence of withdrawal, or to a single exposure/withdrawal regimen. Exposure to APV significantly attenuated the cytotoxicity observed in the primary cell layers of the hippocampus. The present findings suggest that ethanol withdrawal is required to produce NMDA receptor-dependent hippocampal cytotoxicity, particularly in the aging hippocampus in vitro.

Plasticity of GABAA receptors after ethanol pre-exposure in cultured hippocampal neurons

Alcohol use causes many physiological changes in brain with behavioral sequelae. We previously observed (J Neurosci 27:12367-12377, 2007) plastic changes in hippocampal slice recordings paralleling behavioral changes in rats treated with a single intoxicating dose of ethanol (EtOH). Here, we were able to reproduce in primary cultured hippocampal neurons many of the effects of in vivo EtOH exposure on GABA(A) receptors (GABA(A)Rs). Cells grown 11 to 15 days in vitro demonstrated GABA(A)R δ subunit expression and sensitivity to enhancement by short-term exposure to EtOH (60 mM) of GABA(A)R-mediated tonic current (I(tonic)) using whole-cell patch-clamp techniques. EtOH gave virtually no enhancement of mIPSCs. Cells pre-exposed to EtOH (60 mM) for 30 min showed, 1 h after EtOH withdrawal, a 50% decrease in basal I(tonic) magnitude and tolerance to short-term EtOH enhancement of I(tonic), followed by reduced basal mIPSC area at 4 h. At 24 h, we saw considerable recovery in mIPSC area and significant potentiation by short-term EtOH; in addition, GABA(A)R currents exhibited reduced enhancement by benzodiazepines. These changes paralleled significant decreases in cell-surface expression of normally extrasynaptic δ and α4 GABA(A)R subunits as early as 20 min after EtOH exposure and reduced α5-containing GABA(A)Rs at 1 h, followed by a larger reduction of normally synaptic α1 subunit at 4 h, and then by increases in α4γ2-containing cell-surface receptors by 24 h. Measuring internalization of biotinylated GABA(A)Rs, we showed for the first time that the EtOH-induced loss of I(tonic) and cell-surface δ/α4 20 min after withdrawal results from increased receptor endocytosis rather than decreased exocytosis.

Disrupted thalamic T-type Ca2+ channel expression and function during ethanol exposure and withdrawal

Chronic ethanol exposure produces profound disruptions in both brain rhythms and diurnal behaviors. The thalamus has been identified as a neural pacemaker of both normal and abnormal rhythms with low-threshold, transient (T-type) Ca(2+) channels participating in this activity. We therefore examined T-type channel gene expression and physiology in the thalamus of C57Bl/6 mice during a 4-wk schedule of chronic intermittent ethanol exposures in a vapor chamber. We found that chronic ethanol disrupts the normal daily variations of both thalamic T-type channel mRNA levels and alters thalamic T-type channel gating properties. The changes measured in channel expression and function were associated with an increase in low-threshold bursts of action potentials during acute withdrawal periods. Additionally, the observed molecular and physiological alterations in the channel properties in wild-type mice occurred in parallel with a progressive disruption in the normal daily variations in theta (4-9 Hz) power recorded in the cortical electroencephalogram. Theta rhythms remained disrupted during a subsequent week of withdrawal but were restored with the T-type channel blocker ethosuximide. Our results demonstrate that a key ion channel underlying the generation of thalamic rhythms is altered during chronic ethanol exposure and withdrawal and may be a novel target in the management of abnormal network activity due to chronic alcoholism.

Preventive effects of Flos Perariae (Gehua) water extract and its active ingredient puerarin in rodent alcoholism models

BACKGROUND

Radix Puerariae is used in Chinese medicine to treat alcohol addiction and intoxication. The present study investigates the effects of Flos puerariae lobatae water extract (FPE) and its active ingredient puerarin on alcoholism using rodent models.

METHODS

Alcoholic animals were given FPE or puerarin by oral intubation prior or after alcohol treatment. The loss of righting reflex (LORR) assay was used to evaluate sedative/hypnotic effects. Changes of gama-aminobutyric acid type A receptor (GABAAR) subunits induced by alcohol treatment in hippocampus were measured with western blot. In alcoholic mice, body weight gain was monitored throughout the experiments. Alcohol dehydrogenase (ADH) levels in liver were measured.

RESULTS

FPE and puerarin pretreatment significantly prolonged the time of LORR induced by diazepam in acute alcoholic rat. Puerarin increased expression of gama-aminobutyric acid type A receptor alpha1 subunit and decreased expression of alpha4 subunit. In chronic alcoholic mice, puerarin pretreatment significantly increased body weight and liver ADH activity in a dose-dependent manner. Puerarin pretreatment, but not post-treatment, can reverse the changes of gama-aminobutyric acid type A receptor subunit expression and increase ADH activity in alcoholism models.

CONCLUSION

The present study demonstrates that FPE and its active ingredient puerarin have preventive effects on alcoholism related disorders.

Alcohol withdrawal syndromes in the intensive care unit

This article reviews the pathophysiology, diagnosis, and treatment of alcohol withdrawal syndromes in the intensive care unit as well as the literature on the optimal pharmacologic strategies for treatment of alcohol withdrawal syndromes in the critically ill. Treatment of alcohol withdrawal in the intensive care unit mirrors that of the general acute care wards and detoxification centers. In addition to adequate supportive care, benzodiazepines administered in a symptom-triggered fashion, guided by the Clinical Institute Withdrawal Assessment of Alcohol scale, revised (CIWA-Ar), still seem to be the optimal strategy in the intensive care unit. In cases of benzodiazepine resistance, numerous options are available, including high individual doses of benzodiazepines, barbiturates, and propofol. Intensivists should be familiar with the diagnosis and treatment strategies for alcohol withdrawal syndromes in the intensive care unit.

Adolescent ethanol exposure: does it produce long-lasting electrophysiological effects?

This review discusses evidence for long-lasting neurophysiological changes that may occur following exposure to ethanol during adolescent development in animal models. Adolescence is the time that most individuals first experience ethanol exposure, and binge drinking is not uncommon during adolescence. If alcohol exposure is neurotoxic to the developing brain during adolescence, not unlike it is during fetal development, then understanding how ethanol affects the developing adolescent brain becomes a major public health issue. Adolescence is a critical time period when cognitive, emotional, and social maturation occurs and it is likely that ethanol exposure may affect these complex processes. To study the effects of ethanol on adolescent brain, animal models where the dose and time of exposure can be carefully controlled that closely mimic the human condition are needed. The studies reviewed provide evidence that demonstrates that relatively brief exposure to high levels of ethanol, via ethanol vapors, during a period corresponding to parts of adolescence in the rat is sufficient to cause long-lasting changes in functional brain activity. Disturbances in waking electroencephalogram and a reduction in the P3 component of the event-related potential (ERP) have been demonstrated in adult rats that were exposed to ethanol vapor during adolescence. Adolescent ethanol exposure was also found to produce long-lasting reductions in the mean duration of slow-wave sleep (SWS) episodes and the total amount of time spent in SWS, a finding consistent with a premature aging of sleep. Further studies are necessary to confirm these findings, in a range of strains, and to link those findings to the neuroanatomical and neurochemical mechanisms potentially underlying the lasting effects of adolescent ethanol exposure.

Alcohol Pathophysiology

There is no specialized alcohol addiction area in the brain; rather, alcohol acts on a wide range of excitatory and inhibitory nervous networks to modulate neurotransmitters actions by binding with and altering the function of specific proteins. With no hemato-encephalic barrier for alcohol, its actions are strongly related to the amount of intake. Heavy alcohol intake is associated with both structural and functional changes in the central nervous system with long-term neuronal adaptive changes contributing to the phenomena of tolerance and withdrawal. The effects of alcohol on the function of neuronal networks are heterogeneous. Because ethanol affects neural activity in some brain sites but is without effect in others, its actions are analyzed in terms of integrated connectivities in the functional circuitry of neuronal networks, which are of particular interest because of the cognitive interactions discussed in the manuscripts contributing to this review. Recent molecular data are reviewed as a support for the other contributions dealing with cognitive disturbances related to alcohol acute and addicted consumption.

Gene expression in the neuropeptide Y system during ethanol withdrawal kindling in rats

BACKGROUND

Multiple episodes of ethanol intoxication and withdrawal result in progressive, irreversible intensification of the withdrawal reaction, a process termed "ethanol withdrawal kindling." Previous studies show that a single episode of chronic ethanol intoxication and withdrawal causes prominent changes in neuropeptide Y (NPY) and its receptors that have been implicated in regulating withdrawal hyperexcitability. This study for the first time examined the NPY system during ethanol withdrawal kindling.

METHODS

Ethanol withdrawal kindling was studied in rats receiving 16 episodes of 2 days of chronic ethanol intoxication by intragastric intubations followed by 5 days withdrawal. The study included 6 groups: 4 multiple withdrawal episode (MW) groups [peak withdrawal plus (MW+)/minus (MW-) seizures, 3-day (MW3d), and 1-month (MW1mth) withdrawal], a single withdrawal episode group (SW), and an isocalorically fed control group. Gene expression of NPY and its receptors Y1, Y2, and Y5 was studied in the hippocampal dentate gyrus (DG) and CA3/CA1, as well as piriform cortex (PirCx), and neocortex (NeoCx).

RESULTS

MW+/- as well as SW groups showed decreased NPY gene expression in all hippocampal areas compared with controls, but, in the DG and CA3, decreases were significantly smaller in the MW- group compared with the SW group. In the MW+/- and SW groups, Y1, Y2, and Y5 mRNA levels were decreased in most brain areas compared with controls; however, decreases in Y1 and Y5 mRNA were augmented in the MW+/- groups compared with the SW group. The MW+ group differed from the MW- group in the PirCx, where Y2 gene expression was significantly higher.

CONCLUSION

Multiple withdrawal episodes reversibly decreased NPY and NPY receptor mRNA levels at peak withdrawal, with smaller decreases in NPY mRNA levels and augmented decreases in Y1/Y5 mRNA levels compared with a SW episode. Multiple withdrawal-induced seizures increased the Y2 mRNA levels in PirCx. These complex changes in NPY system gene expression could play a role in the ethanol withdrawal kindling process.

The regulation of neuronal gene expression by alcohol

In recent years there has been an explosion of interest in how genes regulate alcohol drinking and contribute to alcoholism. This work has been stimulated by the completion of the human and mouse genome projects and the resulting availability of gene microarrays. Most of this work has been performed in drinking animals, and has utilized the extensive genetic variation among different mouse strains. At the same time, a much smaller amount of effort has gone into the in vitro study of the mechanisms underlying the regulation of individual genes by alcohol. These studies at the cellular and sub-cellular level are beginning to reveal the ways in which alcohol can interact with the transcriptional, translational and post-translational events inside the cell. Detailed studies of the promoter regions within several individual alcohol-responsive genes (ARGs) have been performed and this work has uncovered intricate signaling pathways that may be generalized to larger groups of ARGs. In the last few years several distinct ARGs have been identified from 35,000 mouse genes, by both the "top-down" approach (ex vivo gene arrays) and the "bottom-up" methods (in vitro promoter analysis). These divergent methodologies have converged on a surprisingly small number of genes encoding ion channels, receptors, transcription factors and proteins involved in synaptic function and remodeling. In this review we will describe some of the most interesting cellular and microarray work in the field, and will outline specific examples of genes for which the mechanisms of regulation by alcohol are now somewhat understood.

Tolerance to sedative/hypnotic actions of GABAergic drugs correlates with tolerance to potentiation of extrasynaptic tonic currents of alcohol-dependent rats

Alcohol tolerance resulting from chronic administration is well known to be accompanied by cross-tolerance to sedative/anesthetic drugs, especially those acting on the gamma-aminobutyric acid type A receptors (GABAARs). Rats treated with chronic intermittent ethanol (CIE) show decreased function and altered pharmacology of GABAARs in hippocampal neurons, consistent with cell- and location-specific changes in GABAAR subunit composition. We previously observed variably altered sensitivity to GABAergic drugs in vivo and in hippocampal neurons using whole cell patch-clamp recording in brain slices. Here, we examined additional clinical GABAergic drugs to correlate CIE-induced tolerance to potentiation of neuronal GABAAR-mediated currents with tolerance of these agents to sedative/anesthetic effects in vivo. Typical of several drug classes and two cell types, in CA1 pyramidal neurons, the benzodiazepine diazepam doubled the total charge transfer (TCT) of miniature postsynaptic inhibitory currents (mIPSCs), whereas it quadrupled the TCT of tonic currents. CIE treatment altered these responses to variable extent, as it did to loss of righting reflex (LORR) induced by these same drugs: 90-95% tolerance to flurazepam, the neuroactive steroid alphaxalone, and ethanol; 30-40% to pentobarbital, etomidate, and the GABA agonist gaboxadol; and no tolerance to propofol. There was a strong correlation between tolerance in the LORR assay and tolerance to enhancement of tonic currents, but not mIPSCs. The striking correlation suggests that the sedative/anesthetic actions of GABAergic drugs may be mediated primarily via the potentiation of extrasynaptic GABAARs. This requires the reasonable assumption that the same types of GABAARs in other brain regions involved directly in hypnotic drug actions show similar tolerance.

Dose- and time-dependent expression of anxiety-like behavior in the elevated plus-maze during withdrawal from acute and repeated intermittent ethanol intoxication in rats

BACKGROUND

Withdrawal from acute bolus intraperitoneal (IP) injection of high doses of ethanol elicits anxiety-like behavior (e.g. Doremus et al., 2003; Gauvin et al., 1989, 1992) and conditioned place aversion (Morse et al., 2000). More recently we demonstrated that withdrawal from a single moderate dose of ethanol (2.0 g/kg) is accompanied by elevations in brain reward thresholds, and that repeated intermittent treatment with this dose results in a significant potentiation of reward deficit (Schulteis and Liu, 2006).

METHODS

In the current study, the time- and dose-dependent emergence of anxiety-like behavior was measured in the elevated plus-maze at various times (3 to 24 hours) after acute or 3 daily IP injections of ethanol (1.0, 2.0, or 3.0 g/kg). Rats receiving daily handling for 2 days, and a single anxiety opportunity to explore the maze on a third day were divided into 1 of several treatment protocols: (1) NAIVE conditions: vehicle IP on all 3 days; (2) ACUTE conditions: vehicle on the first 2 days, ethanol on the third day; or (3) REPEAT conditions: ethanol on all 3 days.

RESULTS

ACUTE ethanol elicited reduced exploration of the open arms of the elevated plus-maze in a dose- and time-dependent fashion: 1.0 g/kg failed to elicit any significant effects, whereas 2.0 and 3.0 g/kg ethanol elicited a significant anxiety-like response at 6 hours and 9 to 12 hours postinjection, respectively. REPEAT treatment was still without effect at any time point tested following 1.0 g/kg ethanol, but extended the time course of anxiety-like behavior after treatment with either 2.0 or 3.0 g/kg doses. REPEAT treatment with 2.0 and 3.0 g/kg ethanol also produced significant hypoactivity in the maze at some time points postinjection.

CONCLUSIONS

Withdrawal from a single exposure to ethanol produces transient but significant anxiety-like behavior, and repeated intermittent bouts of intoxication result in a significant extension of the duration of effect. The rapid emergence and progression of negative emotional signs of withdrawal may be a significant factor in determining susceptibility to transition from casual drinking to loss of control and escalating patterns of consumption that result in alcoholism.

Role of the amygdala in ethanol withdrawal seizures

Ethanol withdrawal (ETX) after induction of ethanol dependence results in a syndrome that includes enhanced seizure susceptibility. During ETX in rodents, generalized audiogenic seizures (AGS) can be triggered by intense acoustic stimulation. Previous studies have implicated specific brainstem nuclei in the neuronal network that initiates and propagates AGS during ETX. Although ethanol and ETX are known to affect amygdala neurons, involvement of the amygdala in the network subserving AGS is unclear. Since ethanol and ETX affect N-methyl-d-aspartate (NMDA) receptors in the amygdala, the present study evaluated the effect of focally microinjecting a NMDA antagonist into the amygdala of rats treated with a binge protocol (intragastric administration of ethanol 3 times daily for 4 days). Separate experiments examined extracellular neuronal firing in the amygdala. Cannulae or microwire electrodes were chronically implanted into the amygdala, and changes in seizure behaviors and/or extracellular action potentials were evaluated. Bilateral focal microinjection of a NMDA antagonist, 2-amino-7-phosphonoheptanoate (AP7), into either central nucleus or lateral nucleus of the amygdala (LAMG) significantly reduced AGS. The doses of AP7 and time course of effect were similar in each site, suggesting that both amygdala nuclei participate in the AGS network. Acoustic responses of LAMG neurons were significantly decreased 1 h after the first ethanol dose and also during ETX, as compared to pre-binge controls. However, LAMG neurons consistently exhibited rapid tonic firing during the generalized tonic convulsions of AGS. These findings suggest a critical role of the amygdala in the ETX seizure network in generating tonic convulsions during AGS.

Nicotine stimulation on extracellular glutamate levels in the nucleus accumbens of ethanol-withdrawn rats in vivo

BACKGROUND

Nicotine can release glutamate in the limbic system. Presynaptic activation of glutamate receptors might be relevant for the subsequent firing of excitatory postsynaptic potentials. This might be relevant in early ethanol withdrawal. The effects and differences of nicotine stimulation on glutamate response measured by microdialysis in the nucleus accumbens (NAC) between ethanol-withdrawn rats (EW group) and ethanol-naïve rats (control group) were investigated.

METHODS

Rats were ethanol-intoxicated according to a binge-drinking model: recurrent cycle of 4 days of intoxication (EW group) or 5% sucrose (control group), followed by a 3-day recovery. This was followed by a 2-day intoxication period and subsequent abstinence. After the last oral intake, microdialysis was performed in the left NAC for a 16-hour withdrawal period. At the end of the withdrawal period, a rated withdrawal score (RWS) was documented. Then, nicotine was given subcutaneously at a dose of 0.5 mg/kg and amino acid levels determined by microdialysis were followed for an additional 3 hours.

RESULTS

The RWS was not correlated to the last amount of ethanol received, but was correlated to the total amount of ethanol administered during the pretreatment period: the basal values of extracellular glutamate were found to be decreased in the EW group before withdrawal. Cessation of ethanol significantly increased glutamate levels with a peak between 4 and 10 hours after the last oral intake. Sixteen hours after ethanol withdrawal, the same level as in the control group was achieved. Nicotine significantly increased glutamate levels in the NAC of the EW group but not in ethanol-naïve rats.

CONCLUSIONS

This study showed that withdrawal of ethanol was associated with an increase in extracellular glutamate levels. Systemic administration of nicotine in vivo produced an increase in extracellular levels of glutamate in the core region of the NAC during ethanol withdrawal. This might be a relevant pathomechanism for increased craving either for alcohol or for nicotine after ethanol withdrawal.

Brain reward deficits accompany withdrawal (hangover) from acute ethanol in rats

Withdrawal from an acute bolus injection of ethanol produces affective or emotional signs that include anxiogenic-like behavior and conditioned place aversion. This study assessed whether brain reward deficits that accompany withdrawal from chronic ethanol dependence are also observed upon withdrawal from acute intoxication. Rats were implanted with stimulating electrodes aimed at the medial forebrain bundle in the lateral hypothalamus and trained on a discrete-trial current-intensity brain stimulation reward threshold paradigm. Ethanol intoxication was produced by bolus intraperitoneal injections of ethanol (1.0, 1.5, or 2.0 g/kg). Brain reward thresholds were monitored periodically following the bolus injection (3, 6, 9, 12, 24, 48, 72, 96 h postethanol). Blood samples taken at various intervals postethanol revealed that peak blood alcohol levels (BAL) at all doses tested were reached within 10 min of injection. Following doses of 1.0, 1.5, and 2.0 g/kg ethanol, BAL had declined to undetectable levels within 3-6h postinjection. Withdrawal from a single injection of ethanol resulted in a significant but transient increase in brain reward thresholds only with the highest ethanol dose tested (2.0 g/kg). When acute intoxication and withdrawal episodes were repeated two additional times at weekly intervals, the peak magnitude and duration of threshold elevation increased significantly at the 2.0 g/kg dose of ethanol. A significant but transient increase in thresholds was also seen in the group treated with 1.5 g/kg ethanol during the third and final week of testing. Results indicate that withdrawal from a single exposure to an intoxicating dose of ethanol produces significant brain reward deficits in addition to other affective disturbances previously reported, and that repeated weekly intoxication and withdrawal results in a progressive increase in magnitude and duration of the reward deficit.

Chronic intermittent ethanol-induced switch of ethanol actions from extrasynaptic to synaptic hippocampal GABAA receptors

Alcohol withdrawal syndrome (AWS) symptoms include hyperexcitability, anxiety, and sleep disorders. Chronic intermittent ethanol (CIE) treatment of rats with subsequent withdrawal of ethanol (EtOH) reproduced AWS symptoms in behavioral assays, which included tolerance to the sleep-inducing effect of acute EtOH and its maintained anxiolytic effect. Electrophysiological assays demonstrated a CIE-induced long-term loss of extrasynaptic GABAA receptor (GABAAR) responsiveness and a gain of synaptic GABAAR responsiveness of CA1 pyramidal and dentate granule neurons to EtOH that we were able to relate to behavioral effects. After CIE treatment, the alpha4 subunit-preferring GABAAR ligands 4,5,6,7 tetrahydroisoxazolo[5,4-c]pyridin-3-ol, La3+, and Ro15-4513 (ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo[1,5alpha][1,4]benzodiazepine-3-carboxylate) exerted decreased effects on extrasynaptic currents but had increased effects on synaptic currents. Electron microscopy revealed an increase in central synaptic localization of alpha4 but not delta subunits within GABAergic synapses on the dentate granule cells of CIE rats. Recordings in dentate granule cells from delta subunit-deficient mice revealed that this subunit is not required for synaptic GABAAR sensitivity to low [EtOH]. The profound alterations in EtOH sensitivity and alpha4 subunit localization at hippocampal GABAARs of CIE rats suggest that such changes in these and other relevant brain circuits may contribute to the development of tolerance to the sleep-inducing effects and long-term dependence on alcohol.

Plasticity of GABAA receptors in brains of rats treated with chronic intermittent ethanol

The study of alcohol dependence mechanisms has been aided by work in rodents, where regimens of intermittent chronic administration with repeated episodes of intoxication and withdrawal can be coupled with controlled timing of in vitro studies and the possibility of relating them to behavior. The chronic intermittent ethanol (CIE) model in the rat has been found to be a good model of human alcohol dependence, showing persistent signs of withdrawal and self-administration. Studies in CIE rats suggest that plastic changes in GABA-mediated inhibition involving the GABAA receptor system may be responsible for the behavioral alterations. Here we summarize a combination of evidence that the alcoholic rat CIE model demonstrates changes in GABAA receptor subunit levels, in receptor localization, and in physiology and pharmacology, leading to alterations in behavior that contribute to the hyperexcitable alcohol withdrawal state (anxiety, insomnia, seizure susceptibility) and alcohol dependence.

Comparison of chronic ethanol and chronic intermittent ethanol treatments on the expression of GABA(A) and NMDA receptor subunits

We examined the mRNA and protein levels of GABA(A) and NMDA receptor (NMDAR) subunits in cultured mouse cortical neurons following exposure to chronic ethanol (CE) or chronic intermittent ethanol (CIE), and after 5 days of withdrawal. With respect to GABA(A) receptor mRNA, both treatments decreased the levels of alpha1 and alpha2 subunits, and increased the level of alpha4. However, only CE treatment caused parallel changes in the protein levels; alpha2 and alpha4 protein levels did not change after CIE. Both treatments did not alter beta2 and beta3 mRNA levels, but they increased beta2/3 protein levels. The gamma2 subunit mRNA levels decreased with both treatments, but protein levels did not change. Most of the changes returned to control levels after withdrawal, except for the gamma2 subunit protein, which was lower than controls. In the case of NMDAR subunit, both treatments greatly increased the levels of NR2B mRNA, but barely altered NR1 mRNA and polypeptide levels. CIE treatment caused a relatively higher increase in NR2B protein, and this was the only sustained increase after long-term withdrawal. Taken together, our results show that CIE regimen has less pronounced effects on GABA(A) receptor expression, but increases NR2B expression more dramatically than CE treatment in cultured cortical neurons. These differential effects on subunit expression may result in altered receptor structure and function as a result of ethanol exposure.

Chronic intermittent ethanol exposure enhances NMDA-receptor-mediated synaptic responses and NMDA receptor expression in hippocampal CA1 region

In previous studies, we found that chronic intermittent ethanol (CIE) treatment-a model of ethanol consumption in which animals are exposed to and withdrawn from intoxicating levels of ethanol on a daily basis-produces neuroadaptive changes in hippocampal area CA1 excitatory synaptic transmission and plasticity. Synaptic responses mediated by N-methyl-D-aspartate (NMDA) receptors are known to be sensitive to ethanol and could play an important role in the neuroadaptive changes induced by CIE treatment. To address this issue, we compared electrophysiological recordings of pharmacologically isolated NMDA-receptor-mediated field excitatory postsynaptic potentials (fEPSPs) in the CA1 region of hippocampal slices prepared from control rats and rats exposed to 2 weeks of CIE treatment administered by vapor inhalation. We found that fEPSPs induced by NMDA receptor activation were unaltered in slices prepared shortly after cessation of CIE treatment (i.e., < or = 1 day of withdrawal from CIE). However, following 7 days of withdrawal from CIE treatment, NMDA-receptor-mediated fEPSPs were augmented relative to age-matched controls. Western blot analysis of NMDA receptor subunit expression showed that, at 7 days of withdrawal, the level of protein for NR2A and NR2B subunits was elevated in the CA1 region of hippocampal slices from CIE-treated animals compared with slices from age-matched controls. These results are consistent with an involvement of NMDA-receptor-mediated synaptic responses in the neuroadaptive effects of CIE on hippocampal physiology and suggest that such changes may contribute to ethanol-induced changes in processes dependent on NMDA-receptor-mediated synaptic responses such as learning and memory, neural development, hyperexcitability and seizures, and neurotoxicity.

Estrogen neuroprotection against the neurotoxic effects of ethanol withdrawal: potential mechanisms

Ethanol withdrawal (EW) produces substantial neurotoxic effects, whereas estrogen is neuroprotective. Given observations that both human and nonhuman female subjects often show less impairment following EW, it is reasonable to hypothesize that estrogens may protect females from the neurotoxic effects of ethanol. This article is based on the assumption that the behavioral deficits seen following EW are produced in part by neuronal death triggered by oxidative insults produced by EW. The EW leads to activation of protein kinase C, especially PKCepsilon, which subsequently triggers apoptotic downstream events such as phosphorylation of nuclear factor-kappaB (NFkappaB) complex. On phosphorylation, active NFkappaB translocates to the nucleus, binds to DNA, and activates caspases, which trigger DNA fragmentation and apoptosis. In contrast, estrogens are antioxidant, inhibit overexpression of PKCepsilon, and suppress expression of NFkappaB and caspases. Estrogen treatment reduces the behavioral deficits seen during EW and attenuates molecular signals of apoptosis. The effects of ethanol and estrogen on each step in the signaling cascade from ethanol exposure to apoptosis are reviewed, and potential mechanisms by which estrogen could produce neuronal protection against the neurotoxicity produced by EW are identified. These studies serve as a guide for continuing research into the mechanisms of the neuroprotective effects of estrogen during EW and for the development of potential estrogen-based treatments for male and female alcoholics.

Similar anxiety-like responses in male and female rats exposed to repeated withdrawals from ethanol

Previous research indicated that male rats exhibited anxiety-like behavior following withdrawal from chronic ethanol exposure. This behavior, as well as other symptoms of withdrawal such as seizure susceptibility, may be sensitized in male rats repeatedly withdrawn from chronic ethanol exposure. Because there are sex differences in some alcohol effects, the present study explored whether male and female rats would respond differently to a course of repeated ethanol withdrawals. Similarly aged male and female rats were exposed to a control liquid diet or a diet containing ethanol (7% w/v). Ethanol-exposed rats had only one 5-day cycle of exposure or three cycles, with 2 days of control diet (CD) between cycles. At 5 h after the final ethanol was removed, the rats were placed as same-sexed pairs in the social interaction test; approximately half of the rats were tested later in the elevated plus maze. Rats withdrawn from ethanol after three cycles exhibited reduced the time spent in social interaction and general activity in the social interaction test and reduced the open and closed arm entries in the elevated plus maze. There were no sex differences in these effects. However, male rats exhibited a small anxiety-like response after one cycle of 5 days' exposure to ethanol and female rats did not. Thus, there are no sex differences in the three-cycle multiple-withdrawal paradigm, but there may be differences after briefer exposures.

Electrophysiological Effects of Allopregnanolone in Rats With a History of Ethanol Exposure

BACKGROUND

Sensitivity to the anticonvulsant effects of allopregnanolone (ALLO) is enhanced during the early phase of ethanol (EtOH) withdrawal. However, it is unclear whether this enhanced sensitivity generalizes to ALLO's neurobehavioral effects during protracted abstinence. The purpose of this study was to examine the neurophysiological effects of ALLO in rats with a history of chronic EtOH exposure after a protracted period of abstinence.

METHODS

Male Wistar rats were exposed to EtOH vapor for 14 hr/day for 5 weeks. Blood EtOH levels were maintained between 200 and 250 mg/dl. The effects of ALLO (0.0-10 mg/kg, intraperitoneally) on motor activity, the electroencephalogram (EEG), and auditory event-related potentials then were assessed after 6 to 8 weeks of abstinence from EtOH.

RESULTS

ALLO's effects on the EEG were consistent with previous studies and were unaffected by EtOH exposure. ALLO increased high-frequency EEG power and shifted peak EEG frequencies in a benzodiazepine- and barbiturate-like manner in both the cortex and the hippocampus. The effects of ALLO on event-related potentials were attenuated in rats with a history of EtOH exposure. Low doses of ALLO (1 and 5 mg/kg) reduced cortical P1 amplitude in response to the standard tone but only in the control group. ALLO also increased N1 amplitude in the hippocampus of the control group while having no significant effect in EtOH-exposed rats. Low doses of ALLO (1 and 5 mg/kg) were found to increase motor activity.

CONCLUSIONS

These data indicate that a history of EtOH exposure attenuates some of the neurophysiological effects of ALLO in a manner consistent with cross-tolerance. Taken together, these data suggest that increased sensitivity to ALLO's neurobehavioral effects is limited to the early phases of EtOH withdrawal and may not extend to more protracted periods of abstinence.

Dopamine and alcoholism: neurobiological basis of ethanol abuse

The role of the dopamine (DA) system in brain reward mechanisms and the development of substance abuse has been well established. We review earlier animal and human studies on DA and alcoholism with some relevant issues relating to those studies. The present animal and human data suggest several alterations in the DA system in the context of alcoholism. Receptor studies imply that DA D(2) receptor density and function are lower at least among type 1 alcoholics, which suggests that they could benefit from drugs that enhance DAergic activity, such as partial DA agonists. These drugs could help to restore suboptimal levels of DAergic activity by reducing both the craving for alcohol in abstinence and the euphoria subsequent to alcohol's release of DA in the nucleus accumbens (NAC), thus providing negative reinforcement for relapse.

Neurophysiologic consequences of neonatal ethanol exposure in the rat

Many of the neurotoxic and neurobehavioral consequences of neonatal ethanol exposure in the rat have been characterized. However, in few studies has adult neurophysiologic function been assessed in rats exposed to ethanol during this key developmental period. In the current study, the effects of neonatal ethanol exposure on adult electroencephalographic (EEG) activity and auditory event-related potentials (ERPs) were examined in the rat. Male Sprague-Dawley rats were exposed to ethanol at 6.0 g/kg/day between postnatal days 4 through 9 by using an artificial-rearing procedure. Two control groups were used: a suckle control (SC) group and a gastrostomized control (GC) group. After reaching adulthood (i.e., at 3.5-4 months old), recording electrodes were implanted into the brain of each rat, so that EEG activity and auditory ERPs from the cortex and hippocampus could be assessed. Rats exposed to ethanol during the neonatal period were hyperactive as adults. Assessment of the EEG activity revealed that ethanol exposure increased peak frequency in the frontal cortical and parietal cortical 16-32 Hz frequency bands. Assessment of ERPs revealed that parietal cortical N1 amplitude was reduced in ethanol-exposed rats. Furthermore, parietal cortical N1 latency was increased in the GC group. These findings demonstrate that enhanced motor activity in rats exposed to ethanol during neonatal development occurs in combination with EEG indices of enhanced cortical and hippocampal arousal. Furthermore, a deficiency in cortical N1 amplitude indicates adult rats may have attention deficits. Overall, these results indicate that neonatal ethanol exposure has enduring neurobehavioral consequences, which persist into adulthood. This neurobehavioral profile in the rat is consistent with clinical observations of attention deficits and hyperactivity in children exposed to ethanol during prenatal development.

Imbalance between neuroexcitatory and neuroinhibitory amino acids causes craving for ethanol

Long-term exposure to ethanol leads to an imbalance in different excitatory and inhibitory amino acids. When ethanol consumption is reduced or completely stopped, these imbalances in different amino acids and neurotransmitters are behaviorally expressed in the form of ethanol withdrawal. Glutamate, a major excitatory amino acid, and GABA, a major inhibitory amino acid, are responsible, at least partly, for ethanol withdrawal symptoms. The hypofunction of GABAA receptors and enhanced function of NMDA receptors are suggested to be responsible for the increase in the behavioral susceptibility during ethanol withdrawal. This imbalance between receptors may be exacerbated by repeated withdrawal. Because multiple and repeated periods of chronic ethanol consumption and withdrawal often occur in alcohol abusers, animal studies on the neurochemical changes in different amino acids following chronic ethanol treatment (CET) that is interrupted by repeated ethanol withdrawal episodes may be of clinical relevance for the development of treatment strategies. Brain glutamate increases during the first cycle of ethanol withdrawal, and this increase is much higher during the third cycle of ethanol withdrawal. The elevated glutamate released in the hippocampus during the first cycle of ethanol withdrawal episode was exacerbated in subsequent withdrawal episodes. Acamprosate, a drug used during human alcohol detoxification, is able to completely block the glutamate increase observed during the first as well as the third withdrawal of ethanol. In ethanol-naïve rats, there was no change in the glutamate microdialysate content after an acute ethanol injection. However, when repeated ethanol injections were cued with a vinegar stimulus that had previously been associated with the same ethanol injection, a significant increase in glutamate microdialysate content was assayed. Furthermore, when the cue was omitted, the ethanol injection induced no changes in glutamate microdialysate content in rats that had been previously ethanol conditioned. By comparison, a saline injection had no effect on extracellular glutamate concentration in rats naïve for ethanol as well as in rats daily administered with repeated ethanol injections that were not paired with the cue. It appears probable that these conditioned responses by extracellular glutamate concentrations may participate in the environmental cue-induced conditioned cravings for ethanol that are thought to be related to the high frequency of relapse in detoxified alcoholics.

Consequences of Multiple Withdrawals From Alcohol

This article represents the proceedings of a symposium at the 2003 annual meeting of the Research Society on Alcoholism in Fort Lauderdale, FL, organized by Theodora Duka and chaired by Dai Stephens. The purpose of the symposium was to examine the effects of multiple experiences of withdrawal from alcohol in animals made dependent on alcohol and in humans who are alcohol dependent. Parallels were drawn to the effects of repeated short-lived high-content alcohol exposures in animals and in humans who are social drinkers but indulge in binge drinking. The presentations were (1) Multiple detoxifications and risk of relapse in abstinent alcoholics, by John Gentry and Robert Malcolm; (2) Emotional and cognitive impairments after long-term use of alcohol: relationship to multiple detoxifications and binge drinking, by Theodora Duka; (3) The effect of repeated withdrawal from ethanol on conditioning to appetitive stimuli, by Tamzin Ripley, Gilyanna Borlikova, and Dai Stephens; (4) Alcohol withdrawal kindling: electrographic measures in a murine model of behavioral seizure sensitization, by Lynn Veatch and Howard Becker; and (5) Binge drinking induced changes in CNS, by Fulton Crews.

Integrative Neurobiology of the Alcohol Withdrawal Syndrome???From Anxiety to Seizures

This article represents the proceedings of a symposium presented at the 2003 Research Society on Alcoholism meeting in Ft. Lauderdale, Florida, organized and chaired by Carl L. Faingold. The presentations were (1) Overview, by Carl L. Faingold; (2) Stress, Multiple Alcohol Withdrawals, and Anxiety, by Darin Knapp; (3) Relationship Between Genetic Differences in Alcohol Drinking and Alcohol Withdrawal, by Julia Chester; (4) Neuronal Mechanisms in the Network for Alcohol Withdrawal Seizures: Modulation by Excitatory Amino Acid Receptors, by Carl L. Faingold; and (5) Treatment of Acute Alcohol Withdrawal and Long-Lasting Alterations in Hippocampal Neuronal Networks, by Larry P. Gonzalez. The presentations emphasized the importance of using intact behaving animals to advance the understanding of the human alcohol withdrawal syndrome. This involves applying and amplifying the neurophysiological and neurotransmitter findings observed in vitro to the network-based neurobiological mechanisms that are involved in several important aspects of the specific behaviors observed clinically. The symposium provided evidence that the organizational aspects of neuronal networks in the intact nervous system add another nexus for the action of alcohol and drugs to treat alcohol withdrawal that may not be readily studied in isolated neural elements used in in vitro approaches.

Effects of acamprosate on excitatory amino acids during multiple ethanol withdrawal periods

BACKGROUND

Our previous studies on the effects of acamprosate on enhanced locomotion during repeated withdrawals are now extended to the effects of acamprosate on excitatory amino acids in the hippocampus during repeated ethanol withdrawals.

METHODS

In this study, Wistar rats were made ethanol dependent by 4 weeks of vapor inhalation. After this first cycle of chronic ethanol treatment, rats underwent repeated and alternate cycles of 24 hr withdrawals and 1 week of chronic ethanol treatment. The microdialysis technique was used together with high-performance liquid chromatography and electrochemical detection to quantify different amino acids such as aspartate and glutamate.

RESULTS

An intraperitoneal administration of acamprosate (400 mg/kg) to naïve rats did not alter aspartate or glutamate levels compared with the saline groups. During the first cycle of ethanol withdrawal, the administration of acamprosate (400 mg/kg, intraperitoneally) 2 hr after the commencement of ethanol withdrawal decreased both aspartate and glutamate microdialysate levels when compared with their respective saline group. Acamprosate administration also significantly decreased glutamate levels during the third withdrawal compared with the saline group, whereas no changes were seen in aspartate levels.

CONCLUSION

The results of this work demonstrate that acamprosate reduced the excitatory amino acid glutamate increase observed during repeated ethanol withdrawal. These effects of acamprosate may provide a protective mechanism against neurotoxicity by reducing excitatory amino acids, particularly glutamate.

Withdrawal from chronic intermittent ethanol treatment changes subunit composition, reduces synaptic function, and decreases behavioral responses to positive allosteric modulators of GABAA receptors

One of the pharmacological targets of ethanol is the GABAA receptor (GABAR), whose function and expression are altered after chronic administration of ethanol. The details of the changes differ between experimental models. In the chronic intermittent ethanol (CIE) model for alcohol dependence, rats are exposed to intermittent episodes of intoxicating ethanol and withdrawal, leading to a kindling-like state of behavioral excitability. This is accompanied by presumably causal changes in GABAR expression and physiology. The present study investigates further the effect of CIE on GABAR function and expression. CIE is validated as a model for human alcohol withdrawal syndrome (AWS) by demonstrating increased level of anxiety; diazepam improved performance in the test. In addition, CIE rats showed remarkably reduced hypnotic response to a benzodiazepine and a steroid anesthetic, reduced sensitivity to a barbiturate, but not propofol. Immunoblotting revealed decrease in alpha1 and delta expression and increase in gamma2 and alpha4 subunits in hippocampus of CIE rats, confirmed by an increase in diazepam-insensitive binding for ethyl-8-azido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo(1,5-alpha)(1,4)benzodiazepine-3-carboxylate (Ro15-4513). Elevated mRNA levels were shown for the gamma2S and gamma1 subunits. Recordings in hippocampal slices from CIE rats revealed that the decay time of GABAR-mediated miniature inhibitory postsynaptic currents (mIPSCs) in CA1 pyramidal cells was decreased, and potentiation of mIPCSs by positive modulators of GABAR was also reduced compared with control rats. However, mIPSC potentiation by the alpha4-preferring benzodiazepine ligands bretazenil and Ro15-4513 was maintained, and increased, respectively. These data suggest that specific alterations in GABAR occur after CIE and may underlie the development of hyperexcitability and ethanol dependence.

Consequences of amygdala kindling and repeated withdrawal from ethanol on amphetamine-induced behaviours

It has been shown previously that chronic ethanol treatment in mice leads to accelerated behavioural sensitization to psychomotor stimulants [Manley & Little (1997) J. Pharmacol. Exp. Ther., 281, 1330-1339], whilst repeated experience of ethanol withdrawal sensitizes pathways underlying seizure activity (Becker & Hale (1993) Alcohol Clin. Exp. Res., 17, 94-98]. The aim of the current experiment was to investigate the consequences of repeated withdrawal from ethanol on amphetamine-induced behaviours in the rat and compare this with animals with electrical kindling of the amygdala, a procedure that has been shown to enhance alcohol withdrawal seizures [Pinel et al. (1975) Can. J. Neurol. Sci., 2, 467-475]. For the kindling experiments, electrodes were surgically implanted in the left basolateral amygdala and were stimulated daily at the afterdischarge threshold until a criterion of three consecutive stage 5 seizures was reached. Fully kindled rats showed a marginally significant reduction in sensitivity to the locomotor stimulant effects of acute amphetamine compared with sham and partially kindled rats which had experienced subthreshold stimulation of the amygdala. Sham and partially kindled rats sensitized readily to the locomotor activating effects of amphetamine (0.125 mg/kg) following repeated treatments, but the fully kindled rats did not. Fully kindled rats also failed to show place preference conditioning to amphetamine (0.5 mg/kg). Rats, withdrawn three times from chronic ethanol (liquid-diet), kindled more quickly to PTZ (30 mg/kg, i.p.) than rats with the same overall exposure to ethanol (24 days) followed by a single withdrawal or control animals. However, there was no difference in the locomotor stimulating effects of acute amphetamine (0.25-1 mg/kg, i.p.), the rate of sensitization to amphetamine (0.125 mg/kg, i.p.) or amphetamine induced conditioned place preference (1 mg/kg, i.p.). These observations suggest that, in rats, repeated withdrawal from a relatively mild chronic ethanol treatment modulates neuronal systems that may also be involved in PTZ-induced kindling but not those involved in either the acute stimulant effects of amphetamine or behavioural sensitization or appetitive conditioning following repeated amphetamine administration. Behavioural changes following amygdala kindling differed from those following repeated ethanol withdrawal, suggesting that withdrawal kindling from a mild ethanol treatment differs in its effects from amygdala kindling.

Electrographic and behavioral indices of ethanol withdrawal sensitization

Behavioral and electrographic measures of CNS hyperexcitability were studied in separate groups of mice undergoing multiple ethanol (EtOH) withdrawals in a well-characterized model of EtOH withdrawal sensitization. Consistent with previous studies from this laboratory, mice experiencing repeated cycles of EtOH intoxication and withdrawal exhibited significantly more severe withdrawal seizures (handling-induced convulsions, HIC) in comparison to animals tested following a single withdrawal episode. Spontaneous EEG data collected from a separate group of mice undergoing the same EtOH exposure regimen exhibited a highly-typified alteration during EtOH withdrawal wherein normal EEG was abruptly replaced with high-voltage, repetitive spikes in a frequency range of seven to nine spikes per second. This paroxysmal EEG data, termed 'brief spindle episodes' (BSE) was virtually absent at baseline (prior to EtOH exposure). However, following withdrawal from chronic EtOH exposure, the percent of the EEG recordings containing BSE increased significantly in a time dependent manner. Moreover, in mice undergoing multiple cycles of EtOH exposure and withdrawal, BSE activity progressively increased over successive withdrawal cycles. In contrast, mice tested after repeated cycles of similar handling in the absence of EtOH exposure did not exhibit significant BSE activity until experiencing their one and only EtOH withdrawal episode. Thus, both behavioral and electrographic signs of EtOH withdrawal-related CNS hyperexcitability increased in magnitude during the course of each withdrawal cycle as well as progressively intensifying over successive withdrawal cycles.

Accentuated decrease in social interaction in rats subjected to repeated ethanol withdrawals

BACKGROUND

Previous work has shown that repeated withdrawals from chronic ethanol exposure can kindle seizures in rodents. In this article, the effects of a three-cycle model of ethanol exposure and withdrawal on the social interaction test of anxiety are summarized.

METHODS

Rats were exposed to ethanol (7% or 4.5%) diets over three periods of 5 days, with 2 days of withdrawal between cycles. Between 5 and 6 hr after the ethanol was removed, pairs of rats were placed in open field chambers for the assessment of social interaction behavior and locomotor activity.

RESULTS

After the third cycle of ethanol (7%) presentation, both male and female rats exhibited lower social interaction behavior (more anxiety) and activity than after a single cycle. Rats exposed to a similar amount of ethanol but tested while ethanol was still available did not exhibit a reduction in social interaction. The decrease in social interaction was still present for up to 24 hr but had disappeared by 48 hr after ethanol was withdrawn. When rats were allowed 8 or 16 days to recover from the effects of the three-cycle protocol, a further exposure to 5 days of 7% ethanol diet resulted in a reduction in social interaction on withdrawal similar to that seen from the three-cycle protocol. In contrast, rats exposed continuously to 7% ethanol diet for 15 consecutive days exhibited higher levels of social interaction when maintained on control diet for 8 or 16 days and then reexposed to ethanol. Rats that were exposed to the three-cycle protocol and allowed 32 days to recover before being reexposed to ethanol still had a partial deficit in social interaction. Finally, animals subjected to repeated withdrawals from 4.5% ethanol exhibited a reduction in social interaction without a change in activity after the final withdrawal from ethanol, whereas rats exposed continuously to a 4.5% ethanol diet did not exhibit a reduction in social interaction or activity. Neither blood ethanol concentrations nor changes in body weight could account for these behavioral differences.

CONCLUSION

Repeated withdrawal from ethanol can lead to accentuated or more persistent anxiety-like behavior in rats, as indicated by a decrease in social interaction. The withdrawal-induced decrease in locomotor activity is not accentuated by repeated withdrawals. This model of repeated withdrawals from ethanol may prove useful in defining the neurochemical basis of this accentuation.

The effects of carbamazepine and lorazepam on single versus multiple previous alcohol withdrawals in an outpatient randomized trial

OBJECTIVE

Benzodiazepines are the mainstay of treatment for mild-to-moderate alcohol withdrawal in outpatient settings, but they can interact with alcohol, cause motor incoordination, or be abused. This study compared the therapeutic responses of the benzodiazepine lorazepam and the anticonvulsant carbamazepine for the outpatient treatment of acute alcohol withdrawal in terms of patients' previous detoxification histories, and compared the effects of these 2 medications on drinking behaviors in the immediate postdetoxification period.

DESIGN

This was a randomized double-blind trial comparing patient responses to carbamazepine and lorazepam across 2 levels of detoxification histories (0-1 or >or=2 previous medicated detoxifications).

SETTING

A university medical center substance abuse clinic in Charleston, SC.

PATIENTS

One hundred thirty-six patients in moderate alcohol withdrawal were randomized. Major exclusions were significant hepatic or hematologic abnormalities and use of medications that could alter withdrawal symptoms.

INTERVENTIONS

Patients received 600-800 mg of carbamazepine or 6-8 mg of lorazepam in divided doses on day 1 tapering to 200 mg of carbamazepine or 2 mg of lorazepam.

MAIN OUTCOME MEASURES

The Clinical Institute Withdrawal Assessment for Alcohol-Revised was used to assess alcohol withdrawal symptoms on days 1 through 5 and postmedication at days 7 and 12. Daily drinking was measured by patient report using a daily drinking log and a breath alcohol level with each visit. Side effects were recorded daily.

RESULTS

Carbamazepine and lorazepam were equally effective at decreasing the symptoms of alcohol withdrawal. In the post-treatment period, 89 patients drank on at least 1 day; on average, carbamazepine patients drank less than 1 drink per drinking day and lorazepam patients drank almost 3 drinks per drinking day (P =.003). Among those with multiple past detoxifications, the carbamazepine group drank less than 1 drink per day on average and the lorazepam group drank about 5 drinks per day on average (P =.033). Lorazepam-treated patients had a significant rebound of alcohol withdrawal symptoms post-treatment (P =.007) and the risk of having a first drink was 3 times greater (P =.04) than for carbamazepine-treated patients. Twenty percent of lorazepam-treated patients had dizziness, motor incoordination, or ataxia and did not recognize their impairment. Twenty percent of carbamazepine-treated patients reported pruritus but no rash.

CONCLUSIONS

Carbamazepine and lorazepam were both effective in decreasing the symptoms of alcohol withdrawal in relatively healthy, middle-aged outpatients. Carbamazepine, however, was superior to lorazepam in preventing rebound withdrawal symptoms and reducing post-treatment drinking, especially for those with a history of multiple treated withdrawals.

Periadolescent alcohol exposure has lasting effects on adult neurophysiological function in rats

Most individuals have their first experience with ethanol (EtOH) consumption as adolescents. Episodes of high EtOH drinking, lasting from hours to days (i.e. binges), are not uncommon. Thus, adolescent EtOH drinking has become a significant health concern due to the possible protracted effects of high doses of EtOH on behavior and the developing brain. This study assessed the effects of brief high levels of EtOH during periadolescence on subsequent behavior and electrophysiology in adult rats. Male Sprague-Dawley rats were exposed to EtOH vapor for 5 days (i.e. postnatal days 35-40) or 10 days (i.e. postnatal days 30-40) for 12 h/day. Locomotor activity, EEG activity, and event-related potentials (ERPs) were then assessed at 1 and 6-7 weeks post EtOH exposure. Significant differences in locomotor activity were not observed at 1 week or 6-7 weeks post-ethanol exposure. However, EtOH exposure did have long-term electrophysiological effects. EtOH exposure increased the frequency of the EEG in the 1-2 Hz range in the parietal cortex and the 16-32 Hz range in the hippocampus. EtOH exposure also increased hippocampal N2 amplitude, decreased hippocampal P3 amplitude, and decreased cortical and hippocampal P2 amplitudes. While these findings are generally similar to those reported following long-term ethanol exposure during adulthood, alcohol exposure during adolescence appears to produce more robust hippocampal effects following shorter periods of exposure. In addition, these data indicate that, in the absence of overt behavioral differences, there are long-lasting changes in the functional brain activity of adult rats briefly exposed to high levels of EtOH during the periadolescent period.

Diazepam during prior ethanol withdrawals does not alter seizure susceptibility during a subsequent withdrawal

The number of cycles of alcohol detoxification is suggested to be an important variable in the predisposition to severe withdrawal seizures in alcohol-dependent individuals. Several clinical studies have suggested that exposure to repeated alcohol withdrawals may lead to increased severity of subsequent withdrawal episodes. Consistent with these observations, exposure to multiple cycles of ethanol withdrawal in our previous study significantly increased sensitivity to the convulsive effects of the GABA(A) receptor inverse agonist, Ro15-4513, in comparison to continuous ethanol exposure with no intermittent withdrawals. There was also a selective increase in the occurrence of spontaneous spike and sharp wave (SSW) activity in the EEG recorded from hippocampal area CA(3) in proportion to the number of withdrawal episodes experienced. It is hypothesized that during such repeated episodes of ethanol intoxication and withdrawal, changes in neuronal excitation during prior withdrawals could serve as initially subconvulsive kindling stimuli that might eventually result in the increased severity of the withdrawal syndrome. There is some evidence of the successful suppression of such neuronal excitation during acute ethanol withdrawal by positive modulators of the GABA(A) receptor. In the present study, the benzodiazepine agonist, diazepam, at a dose (4.0 mg/kg) that suppresses acute withdrawal symptoms, when administered during intermittent withdrawals, did not alter seizure sensitivity during a subsequent nonmedicated withdrawal. Diazepam treatment during prior withdrawals also did not have any effect on the multiple withdrawal-associated increase in SSW activity in hippocampal area CA(3) during an untreated withdrawal. This finding suggests that suppression of acute withdrawal symptoms by diazepam does not prevent long-lasting changes in CNS function resulting from repeated exposures to ethanol withdrawal.