Molecular pathogenesis of alcohol withdrawal seizures: the modified lipid-protein interaction mechanism

Gamma-hydroxybutyrate (GHB) for treatment of alcohol withdrawal and prevention of relapses

BACKGROUND

Chronic excessive alcohol consumption may lead to dependence, and to alcohol withdrawal syndrome (AWS) in case of abrupt drinking cessation. Gamma-hydroxybutyric acid (GHB) can prevent and suppress withdrawal symptoms, and improve the medium-term abstinence rate. A clear balance between effectiveness and harmfulness has not been yet established.

OBJECTIVES

To evaluate the efficacy and safety of GHB for treatment of AWS and prevention of relapse

SEARCH STRATEGY

We searched Cochrane Drugs and Alcohol Group' Register of Trials (October 2008), PubMed, EMBASE, CINAHL (January 2005 - October 2008), EconLIT (1969 to February 2008), reference list of retrieved articles

SELECTION CRITERIA

Randomized controlled trials (RCTs) and Controlled Prospective Studies (CPS) evaluating the efficacy and the safety of GHB vs placebo or other pharmacological treatments.

DATA COLLECTION AND ANALYSIS

Three authors independently extracted data and assessed the methodological quality of studies.

MAIN RESULTS

Thirteen RCTs were included. Eleven studies were conducted in Italy.For withdrawal syndrome, comparing GHB 50mg with placebo, results from 1 study, 23 participants favour GHB for withdrawal symptoms: WMD -12.1 (95% CI, -15.9 to -8.29) and side effects were more frequent in the placebo group: RR 16.2 (95% CI, 1.04 to 254.9).In the comparison with Chlormetiazole, for GHB 50mg, results from 1 study, 21 participants favour GHB for withdrawal symptoms: MD -3.40 (95% CI -5.09 to -1.71), for GHB 100mg, results from 1 study, 98 participants favour anticonvulsants for side effects: RR 1.84 (95% CI 1.19 to 2.85).At mid-term, comparing GHB with placebo, results favour GHB for abstinence rate (RR 5.35; 1.28-22.4), controlled drinking (RR 2.13; 1.07-5.54), relapses (RR 0.36; 0.21-0.63), and number of daily drinks (WMD -4.60; -6.18 to -3.02). GHB performed better than NTX and Disulfiram on abstinence (RR 2.59; 1.35-4.98, RR 1.66; 0.99-2.80 respectively). The association of GHB and NTX was better than NTX on abstinence (RR 12.2; 1.79-83.9), as well was the association of NTX, GHB and Escitalopram versus Escitalopram alone (RR 4.58; 1.28-16.5). For Alcohol Craving Scale results favour GHB versus placebo (WMD -1.90; -2.45 to 1.35) and Disulfiram (WMD -1.40; -1.86 to-0.94).

AUTHORS' CONCLUSIONS

GHB 50mg is effective compared to placebo in the treatment of AWS, and in preventing relapses in previously detoxified alcoholics at 3 months follow-up, but the results of this review do not provide sufficient evidence in favour of GHB compared to benzodiazepines and Chlormethiazole for AWS prevention. GHB is better than NTX and Disulfiram in maintaining abstinence and it has a better effect on craving than placebo and Disulfiram. Side effects of GHB are not statistically different from those with BZD, NTX or Disulfiram. However, concern has been raised regarding the risk of developing addiction, misuse or abuse, especially in polydrug abusers.

Diffusion-weighted magnetic resonance imaging at 3.0 Tesla in alcohol intoxication

Acute alcohol intake has pronounced effects on brain function. However, the exact mechanism of action is unclear. Diffusion Magnetic Resonance Imaging (dwMRI) can detect subtle changes in microstructural neural states. Here we tested if dwMRI can detect such changes during alcohol intoxication. We used high-field dwMRI in four healthy subjects at different blood alcohol concentration (0.0 g/L, 0.3 g/L, 0.6 g/L and 1.0 g/L). Although neuropsychological performances declined markedly, no changes in diffusion parameters emerged. First, this finding argues against alcohol-induced diffuse changes of microstructural state and in favour of more specific, possibly receptor-mediated actions of alcohol on brain function. Second, processes involving neurotransmitters that are primarily linked to cognitive function might not be viewable with high-field diffusion MRI.

Hippocampal and striated skeletal muscle changes in fatty acid composition induced by ethanol in alcohol-preferring rats

Chronic ethanol intake affects various organ systems of the body. The present study evaluated modifications of fatty acid concentrations both in brain and striated skeletal muscles of rats genetically selected for voluntary high ethanol intake. Three groups of rats were tracked for 10 weeks of access to ethanol only as fluid (group 1) to free choice of ethanol and water (group 2) or to water only (group 3). At the end of the period, the animals were sacrificed and their brain hippocampus and striated skeletal muscles were removed and fatty acid content of these tissues was determined. Long-chain fatty acid content increased in the hippocampus while it decreased in the striated skeletal muscles. Short chain fatty acid content decreased in the hippocampus while short chain fatty acid content increased in the striated skeletal muscles. The data show that brain and striated skeletal muscles differently modulate fatty acid content perhaps because these areas utilize different cell membrane functionality regulation systems.

Seizures in alcohol-dependent patients: epidemiology, pathophysiology and management

The relationship between alcohol and seizures is complex and multifaceted. The prevalence of epilepsy in alcohol-dependent patients of western industrialised countries may be at least triple that in the general population, whereas the prevalence of alcoholism is only slightly higher in patients with epilepsy than in the general population. The seizure threshold is raised by alcohol drinking and declines on cessation of drinking. As a result, during withdrawal from alcohol, usually 6-48 hours after the cessation of drinking, seizures may occur. Alcohol acts on the brain through several mechanisms that influence seizure threshold. These include effects on calcium and chloride flux through the ion-gated glutamate NMDA and GABA receptors. During prolonged intoxication, the CNS adapts to the effects of alcohol, resulting in tolerance; however, these adaptive effects seem to be transient, disappearing after alcohol intake is stopped. Although the relationship of seizures to alcohol use is likely to be dose dependent and causal, the available clinical data do not suggest that alcohol use results in seizure genesis. However, a genetic predisposition to alcohol withdrawal seizures is possible. Other seizures in alcohol-dependent individuals may be due to concurrent metabolic, toxic, infectious, traumatic, neoplastic and cerebrovascular diseases and are frequently partial-onset seizures. Alcohol abuse is a major precipitant of status epilepticus (9-25% of cases), which may even be the first-ever seizure type. Prompt treatment of alcohol withdrawal seizures is recommended to prevent status epilepticus. During the detoxification process, primary and secondary preventative measures can be taken. A meta-analysis of controlled trials for the primary prevention of alcohol withdrawal seizures demonstrated a highly significant risk reduction for seizures with benzodiazepines and antiepileptic drugs and an increased risk with antipsychotics. A meta-analysis of randomised, placebo-controlled trials for the secondary prevention of seizures after alcohol withdrawal showed lorazepam to be effective, whereas phenytoin was ineffective. Because withdrawal seizures do not recur if the patient remains abstinent, long-term administration of antiepileptic drugs is unnecessary in abstinent patients. The first seizure not related to alcohol withdrawal should not result in permanent drug treatment in an alcohol-dependent patient, because of poor compliance and the high likelihood of remission. The treatment of alcohol dependence is more important and should be prioritised before the prevention of further seizures.

Ethanol withdrawal results in aberrant membrane properties and synaptic responses in periaqueductal gray neurons associated with seizure susceptibility

The midbrain periaqueductal gray (PAG) is implicated as a component of the neuronal network for ethanol withdrawal (ETX) seizures and in other forms of audiogenic seizure (AGS) in rats. Previous in vivo experiments suggest that neurons in the ventrolateral PAG (VL PAG) are required for generation of the clonic and tonic seizure behaviors of AGS. During these seizures, PAG neuronal firing rates increase markedly, but the intracellular events, contributing to this phenomenon, have not been characterized. In the present in vitro study, intracellular current-clamp recordings were obtained from 115 control VL PAG neurons and 71 neurons during ETX. The amount of depolarizing current that needed to be injected into ETX neurons in order to generate an action potential (AP) (N=40) was significantly less than control (N=52). ETX also yielded a significant leftward shift in the frequency-current curve of VL PAG neurons. VL PAG neurons during ETX had significantly enhanced spike firing tendencies, but the firing pattern was similar in ETX and control. ETX significantly increased the incidence of spontaneous APs and the frequency of firing above those in control. A number of cellular properties [e.g. resting membrane potential (RMP), amplitude of AP, AP width at half-height, input resistance and time constant] did not differ significantly between ETX and control neurons. The current-voltage (I-V) relationships of the ETX and control VL PAG neurons were nearly linear between RMP and 80 mV more negative than RMP, whereas the I-V relation was non-linear beyond this range. Stimulation in the dorsolateral PAG in either ETX or control neurons evoked a fast excitatory postsynaptic potential (EPSP) and a slow inhibitory postsynaptic potential (IPSP). The stimulus intensities required to evoke EPSPs were significantly lower than control in neurons during ETX. Epileptiform firing was observed commonly (20%) during ETX but was never seen in control rats. Paired-pulse responses evoked paired-pulse inhibition in approximately 80% of VL PAG neurons from control rats (N=38), which was significantly above the incidence (12%) of this pattern during ETX (N=25). Paired-pulse facilitation was significantly more common (88%) in VL PAG neurons (N=25) during ETX compared to approximately 20% in controls (N=38). These aberrant membrane and synaptic properties provide direct evidence regarding the basis of the hyperexcitability observed in VL PAG neurons in vivo that contribute to propagation mechanisms of clonic and tonic convulsions, occurring during ETX.

The management of alcohol-related seizures: an overview

Alcohol-withdrawal seizures are one of the common medical emergencies. The seizures are generalized and usually occur abruptly between 6-8 hours after cessation of alcohol use (peak 12-24 hours). These patients are often uncooperative and therefore need careful assessment. Lorazepam is the first-line drug for termination and prophylaxis of alcohol-withdrawal seizures.

Glutamate-mediated transmission, alcohol, and alcoholism

Glutamate-mediated neurotransmission may be involved in the range of adaptive changes in brain which occur after ethanol administration in laboratory animals, and in chronic alcoholism in human cases. Excitatory amino acid transmission is modulated by a complex system of receptors and other effectors, the efficacy of which can be profoundly affected by altered gene or protein expression. Local variations in receptor composition may underlie intrinsic regional variations in susceptibility to pathological change. Equally, ethanol use and abuse may bring about alterations in receptor subunit expression as the essence of the adaptive response. Such considerations may underlie the regional localization characteristic of the pathogenesis of alcoholic brain damage, or they may form part of the homeostatic change that constitutes the neural substrate for alcohol dependence.

Inhibition of cardiac sodium currents in adult rat myocytes by n-3 polyunsaturated fatty acids

1. The acute effects of n-3 polyunsaturated fatty acids were determined on whole-cell sodium currents recorded in isolated adult rat ventricular myocytes using patch clamp techniques. 2. The n-3 polyunsaturated fatty acids docosahexaenoic acid (22:6, n-3), eicosapentaenoic acid (20:5, n-3) and alpha-linolenic acid (18:3, n-3) dose-dependently blocked the whole-cell sodium currents evoked by a voltage step to -30 mV from a holding potential of -90 mV with EC50 values of 6.0 +/- 1.2, 16.2 +/- 1.3 and 26.6 +/- 1.3 microM, respectively. 3. Docosahexaenoic acid, eicosapentaenoic acid and alpha-linolenic acid at 25 microM shifted the voltage dependence of activation of the sodium current to more positive potentials by 9.2 +/- 2.0, 10.1 +/- 1.1 and 8.3 +/- 0.9 mV, respectively, and shifted the voltage dependence of inactivation to more negative potentials by 22.3 +/- 0.9, 17.1 +/- 3.7 and 20.5 +/- 1.0 mV, respectively. In addition, the membrane fluidising agent benzyl alcohol (10 mM) shifted the voltage dependence of activation to more positive potentials by 7.8 +/- 2.5 mV and shifted the voltage dependence of inactivation to more negative potentials (by -24.6 +/- 3.6 mV). 4. Linoleic acid (18:2, n-6), oleic acid (18:1, n-9) and stearic acid (18:0) were either ineffective or much less potent at blocking the sodium current or changing the voltage dependence of the sodium current compared with the n-3 fatty acids tested. 5. Docosahexaenoic acid, eicosapentaenoic acid, alpha-linolenic acid and benzyl alcohol significantly increased sarcolemmal membrane fluidity as measured by fluorescence anisotropy (steady-state, rss, values of 0.199 +/- 0. 004, 0.204 +/- 0.006, 0.213 +/- 0.005 and 0.214 +/- 0.009, respectively, compared with 0.239 +/- 0.002 for control), whereas stearic, oleic and linoleic acids did not alter fluidity (the rss was not significantly different from control). 6. The potency of the n-3 fatty acids docosahexaenoic acid, eicosapentaenoic acid and alpha-linolenic acid to block cardiac sodium currents is correlated with their ability to produce an increase in membrane fluidity.