Hand movement speed and accuracy in detoxified alcoholics

Fluoxetine improves behavioural deficits induced by chronic alcohol treatment by alleviating RNA editing of 5-HT2C receptors

The alcoholism and major depressive disorder are common comorbidity, with alcohol-induced depressive symptoms being eased by selective serotonin re-uptake inhibitors (SSRIs), although the mechanisms underlying pathology and therapy are poorly understood. Chronic alcohol consumption affects the activity of serotonin 2C receptors (5-HT_2CR) by regulating adenosine deaminases acting on RNA (ADARs) in neurons. Astrogliopathic changes contribute to alcohol addiction, while decreased release of ATP from astrocytes can trigger depressive-like behaviours in mice. In this study, we discovered that chronic alcohol treatment increased editing of RNA of 5-HT_2CR via up-regulating the expression of ADAR2, consequently reducing the release of ATP from astrocytes induced by 5-HT_2CR agonist, MK212. Moreover, SSRI antidepressant fluoxetine decreased the expression of ADAR2 through the transactivation of EGFR/PI3K/AKT/cFos signalling pathway. The increased release of astroglial ATP by MK212 which was suppressed by chronic alcohol consumption, and reduction in ADAR2 activity eliminated the RNA editing of 5-HT_2CR increased by alcohol in vitro and recovered the release of ATP from astrocytes induced by MK212. Meanwhile, fluoxetine improved the behavioural and motor symptoms induced by alcohol addiction and decreased the alcohol intake. Our study suggests that the astrocytic 5-HT_2CR contribute to alcohol addiction; fluoxetine thus can be used to alleviate depression, treat alcohol addiction and improve motor coordination.

Complex interactions between the subject factors of biological sex and prior histories of binge-drinking and unpredictable stress influence behavioral sensitivity to alcohol and alcohol intake

Alcohol use disorders, affective disorders and their comorbidity are sexually dimorphic in humans. However, it is difficult to disentangle the interactions between subject factors influencing alcohol sensitivity in studies of humans. Herein, we combined murine models of unpredictable, chronic, mild stress (UCMS) and voluntary binge-drinking to examine for sex differences in the interactions between prior histories of excessive ethanol-drinking and stress upon ethanol-induced changes in motor behavior and subsequent drinking. In Experiment 1, female mice were insensitive to the UCMS-induced increase in ethanol-induced locomotion and ethanol intake under continuous alcohol-access. Experiment 2 revealed interactions between ethanol dose and sex (females>males), binge-drinking history (water>ethanol), and UCMS history (UCMS>controls), with no additive effect of a sequential prior history of both binge drinking and UCMS observed. We also observed an interaction between UCMS history and sex for righting recovery. UCMS history potentiated subsequent binge-drinking in water controls of both sexes and in male binge-drinking mice. Conversely, a prior binge-drinking history increased subsequent ethanol intake in females only, irrespective of prior UCMS history. In Experiment 3, a concurrent history of binge-drinking and UCMS did not alter ethanol intake, nor did it influence the ethanol dose-locomotor response function, but it did augment alcohol-induced sedation and reduced subsequent alcohol intake over that produced by binge-drinking alone. Thus, the subject factors of biological sex, prior stressor history and prior binge-drinking history interact in complex ways in mice to impact sensitivity to alcohol's motor-stimulating, -incoordinating and intoxicating effects, as well as to influence subsequent heavy drinking.

Alcohol Withdrawal and Cerebellar Mitochondria

Cerebellar disorders trigger the symptoms of movement problems, imbalance, incoordination, and frequent fall. Cerebellar disorders are shown in various CNS illnesses including a drinking disorder called alcoholism. Alcoholism is manifested as an inability to control drinking in spite of adverse consequences. Human and animal studies have shown that cerebellar symptoms persist even after complete abstinence from drinking. In particular, the abrupt termination (ethanol withdrawal) of long-term excessive ethanol consumption has shown to provoke a variety of neuronal and mitochondrial damage to the cerebellum. Upon ethanol withdrawal, excitatory neurotransmitter molecules such as glutamate are overly released in brain areas including cerebellum. This is particularly relevant to the cerebellar neuronal network as glutamate signals are projected to Purkinje neurons through granular cells that are the most populated neuronal type in CNS. This excitatory neuronal signal may be elevated by ethanol withdrawal stress, which promotes an increase in intracellular Ca(2+) level and a decrease in a Ca(2+)-binding protein, both of which result in the excessive entry of Ca(2+) to the mitochondria. Subsequently, mitochondria undergo a prolonged opening of mitochondrial permeability transition pore and the overproduction of harmful free radicals, impeding adenosine triphosphate (ATP)-generating function. This in turn provokes the leakage of mitochondrial molecule cytochrome c to the cytosol, which triggers a cascade of adverse cytosol reactions. Upstream to this pathway, cerebellum under the condition of ethanol withdrawal has shown aberrant gene modifications through altered DNA methylation, histone acetylation, or microRNA expression. Interplay between these events and molecules may result in functional damage to cerebellar mitochondria and consequent neuronal degeneration, thereby contributing to motoric deficit. Mitochondria-targeting research may help develop a powerful new therapy to manage cerebellar disorders associated with hyperexcitatory CNS disorders like ethanol withdrawal.

Ethanol-Induced Alterations in Purkinje Neuron Dendrites in Adult and Aging Rats: a Review

Uncomplicated alcoholics suffer from discrete motor dysfunctions that become more pronounced with age. These deficits involve the structure and function of Purkinje neurons (PN), the sole output neurons from the cerebellar cortex. This review focuses on alterations to the PN dendritic arbor in the adult and aging Fischer 344 rat following lengthy alcohol consumption. It describes seminal studies using the Golgi-Cox method which proposed a model for ethanol-induced dendritic regression. Subsequent ultrastructural studies of PN dendrites showed dilation of the extensive smooth endoplasmic reticulum (SER) which preceded and accompanied dendritic regression. The component of the SER that was most affected by ethanol was the sarco/endoplasmic reticulum Ca(2+) ATPase pump (SERCA) responsible for resequestration of calcium into the SER. Ethanol-induced decreases in SERCA pump levels, similar to the finding of SER dilation, preceded and occurred concomitantly with dendritic regression. Discrete ethanol-induced deficits in balance also accompanied these decreases. Ethanol-induced ER stress within the SER of PN dendrites was proposed as an underlying cause of dendritic regression. It was recently shown that increased activation of caspase 12, inherent to the ER, occurred in PN of acute slices in ethanol-fed rats and was most pronounced following 40 weeks of ethanol treatment. These findings shed new light into alcohol-induced disruption in PN dendrites providing a new model for the discrete but critical changes in motor function in aging, adult alcoholics.

Sex and gender-related differences in alcohol use and its consequences: Contemporary knowledge and future research considerations

AIMS

To review the contemporary evidence reflecting male/female differences in alcohol use and its consequences along with the biological (sex-related) and psycho-socio-cultural (gender-related) factors associated with those differences.

METHODS

MEDLINE, PubMed, Web of Science, SCOPUS, PsycINFO, and CINAHL databases were searched for relevant publications, which were subsequently screened for the presence/absence of pre-specified criteria for high quality evidence.

RESULTS

Compared to men, more women are lifetime abstainers, drink less, and are less likely to engage in problem drinking, develop alcohol-related disorders or alcohol withdrawal symptoms. However, women drinking excessively develop more medical problems. Biological (sex-related) factors, including differences in alcohol pharmacokinetics as well as its effect on brain function and the levels of sex hormones may contribute to some of those differences. In addition, differences in alcohol effects on behavior may also be driven by psycho-socio-cultural (gender-related) factors. This is evident by variation in the magnitude of differences in alcohol use between countries, decreasing difference in the rates of alcohol consumption in recent generations and other findings. Evidence indicates that both sex and gender-related factors are interacting with alcohol use in complex manner, which differentially impacts the risk for development of the behavioral or medical problems and alcohol use disorders in men and women.

CONCLUSIONS

Discovery of the mechanisms underlying biological (sex-related) as well as psycho-socio-cultural (gender-related) differences in alcohol use and related disorders is needed for development of personalized recommendations for prevention and treatment of alcohol use disorders and related problems in men and women.

Alcohol use across the lifespan: An analysis of adolescent and aged rodents and humans

Adolescence and old age are unique periods of the lifespan characterized by differential sensitivity to the effects of alcohol. Adolescents and the elderly appear to be more vulnerable to many of alcohol's physiological and behavioral effects compared to adults. The current review explores the differential effects of acute alcohol, predominantly in terms of motor function and cognition, in adolescent and aged humans and rodents. Adolescents are less sensitive to the sedative-hypnotic, anxiolytic, and motor-impairing effects of acute alcohol, but research results are less consistent as it relates to alcohol's effects on cognition. Specifically, previous research has shown adolescents to be more, less, and similarly sensitive to alcohol-induced cognitive deficits compared to adults. These equivocal findings suggest that learning acquisition may be differentially affected by ethanol compared to memory, or that ethanol-induced cognitive deficits are task-dependent. Older rodents appear to be particularly vulnerable to the motor- and cognitive-impairing effects of acute alcohol relative to younger adults. Given that alcohol consumption and abuse is prevalent throughout the lifespan, it is important to recognize age-related differences in response to acute and long-term alcohol. Unfortunately, diagnostic measures and treatment options for alcohol dependence are rarely dedicated to adolescent and aging populations. As discussed, although much scientific advancement has been made regarding the differential effects of alcohol between adolescents and adults, research with the aged is underrepresented. Future researchers should be aware that adolescents and the aged are uniquely affected by alcohol and should continue to investigate alcohol's effects at different stages of maturation.

Profiles of impaired, spared, and recovered neuropsychologic processes in alcoholism

Long-term chronic alcoholism is associated with disparate and widespread residual consequences for brain functioning and behavior, and alcoholics suffer a variety of cognitive deficiencies and emotional abnormalities. Alcoholism has heterogeneous origins and outcomes, depending upon factors such as family history, age, gender, and mental or physical health. Consequently, the neuropsychologic profiles associated with alcoholism are not uniform among individuals. Moreover, within and across research studies, variability among subjects is substantial and contributes to characteristics associated with differential treatment outcomes after detoxification. In order to refine our understanding of alcoholism-related impaired, spared, and recovered abilities, we focus on five specific functional domains: (1) memory; (2) executive functions; (3) emotion and psychosocial skills; (4) visuospatial cognition; and (5) psychomotor abilities. Although the entire brain might be vulnerable in uncomplicated alcoholism, the brain systems that are considered to be most at risk are the frontocerebellar and mesocorticolimbic circuitries. Over time, with abstinence from alcohol, the brain appears to become reorganized to provide compensation for structural and behavioral deficits. By relying on a combination of clinical and scientific approaches, future research will help to refine the compensatory roles of healthy brain systems, the degree to which abstinence and treatment facilitate the reversal of brain atrophy and dysfunction, and the importance of individual differences to outcome.

Time course of SERCA 2b and calreticulin expression in Purkinje neurons of ethanol-fed rats with behavioral correlates

Chronic ethanol consumption for 40 weeks in adult rats results in dilation of the extensive smooth endoplasmic reticulum (SER), a major component of the calcium homeostatic system within Purkinje neuron (PN) dendrites.

AIMS

The aim of the present study was to determine whether chronic ethanol consumption results in alterations of the sarco/endoplasmic reticulum Ca(2+) ATPase pump (SERCA) on the SER membrane of PN dendrites. The density of calreticulin, a calcium chaperone, was also investigated in the PN along with balancing ability.

METHODS

Ninety 8-month-old rats were exposed to rat chow, the AIN-93 M liquid control or ethanol diets (30/diet) for a duration of 10, 20 or 40 weeks (30/duration). Age changes relative to the rat chow controls were assessed with 3-month-old control rats (n = 10). Balance was assessed prior to euthanasia. Quantitative immunocytochemistry was used to determine the density of SERCA 2b + dendrites and calreticulin + PN soma and nuclei. Molecular layer volumes were also determined.

RESULTS

Following 40 weeks of ethanol treatment, there were ethanol-induced decreases in SERCA 2b densities within the dendritic arbor and decreased balancing ability on the more difficult round rod balance test. There were no ethanol-induced changes in calreticulin densities.

CONCLUSION

It can be concluded that ethanol-induced decreases in the SERCA pump accompany SER dilation and contribute to previously reported ethanol-induced dendritic regression in PN. Ethanol-induced changes in balance also occurred. Chronic ethanol consumption does not alter calreticulin expression in PN.

Cognitive functions in abstinent alcohol-dependent patients

The objective of this cross-sectional study was to compare cognitive functioning of abstaining alcohol-dependent (AD) male patients and healthy controls as well as to investigate whether their cognitive performance varied by abstinence length. Forty-two maintaining abstinent (AD) patients and 34 healthy controls were examined. Tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB) were used to assess cognitive functions. Differences in cognitive performance were found between AD patients and healthy controls. Nonverbal tasks in cognitive domains such as attention, visual memory and working memory were impaired in AD patients who presented deficits in visual episodic memory, had slower reaction time and reduced working memory span. Patients who were abstinent for less than one year made more errors in both attentional set shifting and working memory tests than healthy controls and patients with longer durations of abstinence. Impairments identified in multiple cognitive domains in abstinent alcohol-dependent subjects suggest functional deficits in extensive brain networks connecting interrelated brain structures. Attentional control and spatial working memory were less impaired in those AD patients who maintained abstinence for at least one year.

Ethanol-related increases in degenerating bodies in the Purkinje neuron dendrites of aging rats

Chronic ethanol consumption in aging rats results in regression of Purkinje neuron (PN) dendritic arbors ([Pentney, 1995 Measurements of dendritic pathlengths provide evidence that ethanol-induced lengthening of terminal dendritic segments may result from dendritic regression. Alcohol Alcohol. 30, 87-96]), loss of synapses (Dlugos and Pentney, 1997), dilation of the smooth endoplasmic reticulum (SER), and the formation of degenerating bodies within PN dendrites ([Dlugos, C.A., 2006a. Ethanol-Related Smooth Endoplasmic Reticulum Dilation in Purkinje Dendrites of Aging Rats. Alcohol., Clin. Exp. Res. 30, 883-891,Dlugos, C.A., 2006b. Smooth endoplasmic reticulum dilation and degeneration in Purkinje neuron dendrites of aging ethanol-fed female rats. Cerebellum. 5, 155-162]). Dilation of the SER and the formation of degenerating bodies may be a predictor of dendritic regression. Ethanol-induced effects on mitochondria may be involved as mitochondria cooperate with the SER to maintain calcium homeostasis. The purpose of this study was to determine whether degenerating body number and mitochondrial density and structure are altered by chronic ethanol treatment in PN dendrites. Male, Fischer 344 rats, 12 months of age, were fed an ethanol or pair-fed liquid diet, or rat chow for a period of 10, 20, or 40 weeks (15 rats/treatment; 45 rats/treatment duration). Ethanol-fed rats received 35% of their calories as ethanol. At the end of treatment, all animals were euthanized, perfused, and tissue prepared for electron microscopy. The densities of degenerating bodies and mitochondria, mitochondrial areas, and the distance between the SER and the mitochondria were measured. Results showed that there was an ethanol-related increase in degenerating bodies compared to controls at 40 weeks. Ethanol-induced alterations to mitochondria were absent. Correlation of the present results with those of previous studies suggest that degenerating bodies may be formed from membrane reabsorption during dendritic regression or from degenerating SER whose function has been compromised by dilation.

Motor functioning and alcohol dependence

BACKGROUND

Autopsy and neuroimaging research in stably abstinent alcoholics illuminated structural and functional abnormalities in brain areas that organize and coordinate motor functioning. Researchers that used behavioural tasks to measure motor functioning found that abstinent alcoholics perform worse than healthy controls. These researchers however did not analyze timed responses into their cognitive and motor components. They thus were unable to decide which aspects of information processing are impaired. We here used a Fitts' task to examine differences in cognitive and motor components between abstinent alcoholics and healthy controls.

METHODS

Fifty-two abstinent alcoholics and 52 healthy controls participated in this research design. Fine motor functioning was assessed by means of the Fitts' task.

RESULTS

Abstinent alcoholics needed more time to perform timed responses than healthy controls. As both reaction and movement times were higher in abstinent alcoholics, both cognitive and motor processes seem to be impaired. When the task became more difficult (small targets instead of large targets) abstinent alcoholics needed proportionally more time to give the correct response than healthy controls. This phenomenon solely applied to movement times.

CONCLUSIONS

These research data indicate that abstinent alcoholics are somewhat impaired on a behavioral level. The execution of timed responses indeed was lengthier in abstinent alcoholics than in healthy controls. As both cognitive and motor processes were impaired, we here assume that both central and peripheral processes are affected by progressive alcohol intake. Abstinent alcoholics also have more difficulties to adapt their motor responses to changing task conditions.

Compromised pontocerebellar and cerebellothalamocortical systems: speculations on their contributions to cognitive and motor impairment in nonamnesic alcoholism

BACKGROUND

Corticopontocerebellar and cerebellothalamocortical circuits underlie a wide range of neuropsychological processes compromised by alcoholism. The analyses herein tested whether abnormalities of volumes of brain structures forming nodes of these separate feed-forward and feedback systems are selectively related to each other and whether any of these noncortical regions can account for cognitive and motor deficits occurring as sequelae of chronic alcoholism.

METHODS

Regional brain measures originated from our prior neuroimaging studies, showing in alcoholics significant volume deficits in the principal structures of interest: cerebellar hemispheres, vermis, pons, and thalamus as well as prefrontal, frontal, and parietal cortex. Neuropsychological functions targeted for analysis-problem solving, visuospatial ability, and static postural stability-showed 0.6 to 1.6 SD deficits in these alcoholic men.

RESULTS

In alcoholics, the patterns of correlations were consistent with dissociation of thalamic and pontine circuitry. Pontine and thalamic volumes were not correlated with each other. Pontine volumes correlated with white matter volumes of anterior superior vermis and gray and white matter volumes of the cerebellar hemispheres but not with cortical regional volumes. Thalamic volumes correlated with gray matter volumes of the cerebellar hemispheres, parietal cortex, and inferior posterior vermian lobule, which itself correlated with parietal, prefrontal, and frontal cortical volumes. Controls did not show these correlational patterns. Brain structure-function relationships in alcoholics examined with multiple regression identified anterior vermian but not prefrontal or parietal volume as a unique predictor of balance scores; vermian and thalamic but not prefrontal cortical volumes as predictors of card sorting scores; and cerebellar hemispheric white matter but not parietal cortical volume as a predictor of visuospatial ability.

CONCLUSIONS

Each major node of frontocerebellar circuitry shows volume deficits in alcoholics but can be independently compromised. Disruption of these circuits may underlie alcoholism-related neuropsychological deficits, either by abnormalities present in individual nodes or by disconnection via interruption of selective circuitry.

Role of parasympathetic (vagal) cardiac control in elevated heart rates of smokers

Smokers may develop chronic increases in cardiac rate and alterations in cardiovascular control. If the increased mean heart rate (HR) in cigarette smokers is due in part to a deficit in vagal cardiac rate control, this should be reflected in a decreased amplitude of respiratory sinus arrhythmia (RSA). To test this hypothesis we studied 36 smokers and 36 non-smokers, matched for age, race, gender and blood pressure. All subjects were studied in the supine and seated positions. Mean heart rate was determined from the ECG during 30 s of quiet breathing; RSA was determined for 10 consecutive deep (>50% vital capacity) slow (5-7/min) breaths. Mean HRs in smokers were significantly higher than in non-smokers, but the increases in mean HRs evoked by a shift from the supine to seated position were lower in smokers than in non-smokers, suggesting that chronic tobacco use may alter the relative contributions of sympathetic and parasympathetic control of cardiac rate. Because neither the RSAs nor the position-dependent increase in RSA were different between smokers and non-smokers, we conclude that the elevated mean HRs in smokers were not the result of decreased respiratory or vasomotor modulation of vagal cardiac control, but instead were the result primarily of sympathetic stimulation.

Chronic alcoholism and the frontal lobe: which executive functions are imparied?

OBJECTIVE

Over the last decade, various hypotheses have been advanced concerning the cognitive functions affected by chronic alcoholism. The aim of this study was to identify the pattern of executive function impairment in chronic alcoholism, shedding light on possible differences between specific functions related to the frontal lobe.

METHODS

Twenty-two male alcoholics and 22 controls, matched for age, educational level and IQ, were enrolled in the study. MMPI and a battery of neuropsychological tests [i.e. digit symbol, trail making test, Stroop test, digit cancellation test, Wisconsin card sorting test (WCST), simple and choice reaction times] for assessing frontal lobe functioning were administered.

RESULTS

The alcoholics were found to be impaired in a wide range of executive domains, with the exception of the Stroop test, which nevertheless showed a trend towards statistically significant differences between patients and controls.

CONCLUSION

With the exception of aggression - our subjects did not have high aggression scale scores - the 'frontal lobe hypothesis', according to which alcoholic patients are impaired on function tests related to the frontal lobe, was therefore confirmed in our sample.

Gender, health beliefs, health behaviors, and alcohol consumption

We conducted a study of the relationship between health beliefs, health practices, and alcohol consumption among women and men using the Health Belief Model (HBM). The study sample (N = 41,104) was drawn from the 1990 National Health Interview Survey. A 15% random sample was selected from the total data set for the purpose of selecting variables. Alcohol consumption was defined as a health-related behavior and was regressed on demographic characteristics, health beliefs, and health practices. Quantity and frequency of alcohol consumption were assessed for each gender, using the HBM. The HBM explained similar amounts of the variance in alcohol use for women and men. Quantity of alcohol consumed accounted for more variance than did frequency of consumption. We conclude that health beliefs and behaviors are related to alcohol consumption after adjustment for demographic characteristics, and that differences exist between perceived risks and behaviors for both women and men.

Residual pressor effects of chronic alcohol in detoxified alcoholics

Although research in population studies has indicated that recent alcohol intake is positively correlated with blood pressure, there is a need to study the relationship of blood pressure to measures of lifetime alcohol intake in alcoholics. To this end, we assessed systolic and diastolic pressures and lifetime alcohol intake through structured interviews with 253 normotensive recovering alcoholics. Blood pressures were first corrected with multiple linear regression for the influence of confounding or modifying variables and then were regressed against alcohol consumption measures. Systolic pressure was significantly correlated (positively) with only a few measures of recent alcohol intake, and the correlations were not high (r2 = .05 to .11, P < .05). Diastolic pressure was found to be highly and positively correlated with the duration of the drinking career, but more so in blacks than in whites. The total lifetime dose of alcohol was found to be positively correlated with diastolic but not systolic pressure, but only in black male alcoholics. The steeper slope of the regression of blood pressure versus lifetime total alcohol or duration of the drinking career in black alcoholics suggests greater cardiovascular susceptibility to alcohol toxicity as lifetime doses increase and as the drinking career lengthens.

Application of bioelectric impedance methodology and prediction equations to determine the volume of distribution for ethanol

In large-scale epidemiologic studies of drinking behavior there is a need for simple and reliable estimates of the body water compartment of subjects. This, in turn, provides an estimate of the volume of distribution of ingested ethanol and a better estimate of tissue exposure levels than the use of total body weight as the volume of distribution for alcohol. The volume of distribution for ethanol (total body water, TBW) was estimated in a racially mixed group of 276 alcoholics and 166 nonalcoholics (aged 20-59 years) by means of bioelectric impedance methodology (BIA) and by means of prediction equations based upon age, body weight, and height. Estimations of mean TBW from BIA were found to be only slightly higher (1-4%) than those provided by the prediction equations. TBW values generated from both prediction equations were also highly correlated with TBW values obtained by impedance methodology, with the highest correlations observed in females (particularly black) and in alcoholics (particularly female).

Drinking patterns and health status in smoking and nonsmoking alcoholics

Alcoholics who smoked also reported that they drank more frequently and consumed more alcohol on drinking occasions than alcoholics who did not smoke, a practice that resulted in a substantially greater lifetime alcohol consumption in the smokers. Smoking alcoholics also consumed more cigarettes and reported more smoking-related physical symptoms than social drinkers who smoked. The heart rates (HRs) of smoking and nonsmoking alcoholics were similar and both exceeded the HRs for the smoking social drinkers by approximately 13 beats/min (bpm) in males and by approximately 7 bpm in females. Surprisingly, correlations between HR and lifetime alcohol consumption were higher and slopes were steeper in controls than in alcoholics. HRs in a subset of the male alcoholics fell only approximately 3 bpm after 24 weeks of abstinence, but changed no further over an additional 24-week period. Taken together, the findings suggest that HRs may have been higher in this group of alcoholics before the onset of alcohol abuse and that alcohol intake contributed only slightly to the high HR.

Depression of an inhibitory reflex, the masseteric silent period, in recovering alcoholics

Because inhibitory deficits may contribute to motor incoordination of alcoholics, we proposed that the duration of the masseteric silent period (SP), an inhibitory reflex, might be shorter in alcoholics (ALs) than in nonalcoholics (NAs). To test this hypothesis, we measured the SP in a racially mixed group of 12 ALs and 12 NAs matched for age (31-49 years) and sex. All subjects were normotensive, had full dentition, and reported no major medical problems. Sensory and motor conduction velocities of the anterior tibialis, ulnar, and medial nerves were measured for each subject, and were not different in ALs and NAs. Jaw jerk and SP were evoked by tapping the chin manually with a rubber hammer containing a circuit to trigger the oscilloscope display of the masseter EMGs. Averaged mean latencies and durations of the SPs were not significantly different between the right and left masseters. SP latencies were significantly (0.7 msec) shorter in ALs than NAs (p < 0.01). The mean SP duration for ALs (13.9 +/- 1.6 msec) was also significantly shorter than that of the NAs (24.4 +/- 2.4 msec; p < 0.001). Results support the hypothesis that chronic alcoholism may interfere with inhibitory mechanisms in the CNS.