Experimental alcoholic neuropathy in the rat: histological and electrophysiological study on the myoneural junctions and the peripheral nerves

Neuromuscular mechanisms of weakness in a mouse model of chronic alcoholic myopathy

BACKGROUND

Weakness is a common clinical symptom reported in individuals with chronic alcohol use disorder. However, it remains unclear whether low strength in these individuals is directly related to excessive ethanol intake, other deleterious factors (lifestyle, environment, genetics, etc.), or a combination of both. Therefore, we examined whether (and how) ethanol reduces the muscle's force-producing capacity using a controlled in vivo preclinical mouse model of excessive ethanol intake.

METHODS

To establish whether chronic ethanol consumption causes weakness, C57BL/6 female mice consumed 20% ethanol for 40 weeks (following a 2-week ethanol ramping period), and various measures of muscular force were quantified. Functional measures included all-limb grip strength and in vivo contractility of the left ankle dorsiflexors and plantarflexors. Once confirmed that mice consuming ethanol were weaker than age-matched controls, we sought to determine the potential neuromuscular mechanisms of muscle dysfunction by assessing neuromuscular excitation, muscle quantity, and muscle quality.

RESULTS

Mice consuming chronic ethanol were 13 to 16% weaker (p ≤ 0.016) than controls (i.e., mice consuming 100% water) with the negative impact of ethanol on voluntary grip strength (ƞ²  = 0.603) being slightly larger than that of electrically stimulated muscle contractility (ƞ²  = 0.482). Relative to controls, lean mass and muscle wet masses were 9 to 16% lower in ethanol-consuming mice (p ≤ 0.048, ƞ²  ≥ 0.268). No significant changes were observed between groups for indices of neuromuscular excitation at the level of the motor unit, neuromuscular junction, or plasmalemma (p ≥ 0.259, ƞ²  ≤ 0.097), nor was muscle quality altered after 40 weeks of 20% ethanol consumption (p ≥ 0.695, ƞ²  ≤ 0.012).

CONCLUSIONS

Together, these findings establish that chronic ethanol consumption in mice induces a substantial weakness in vivo that we interpret to be primarily due to muscle atrophy (i.e., reduced muscle quantity) and possibly, to a lesser degree, loss of central neural drive.

An overview of animal models of pain: disease models and outcome measures

Pain is ultimately a perceptual phenomenon. It is built from information gathered by specialized pain receptors in tissue, modified by spinal and supraspinal mechanisms, and integrated into a discrete sensory experience with an emotional valence in the brain. Because of this, studying intact animals allows the multidimensional nature of pain to be examined. A number of animal models have been developed, reflecting observations that pain phenotypes are mediated by distinct mechanisms. Animal models of pain are designed to mimic distinct clinical diseases to better evaluate underlying mechanisms and potential treatments. Outcome measures are designed to measure multiple parts of the pain experience, including reflexive hyperalgesia measures, sensory and affective dimensions of pain, and impact of pain on function and quality of life. In this review, we discuss the common methods used for inducing each of the pain phenotypes related to clinical pain syndromes as well as the main behavioral tests for assessing pain in each model.

PERSPECTIVE

Understanding animal models and outcome measures in animals will assist in translating data from basic science to the clinic.

Experimental model of alcohol-related peripheral neuropathy

INTRODUCTION

The aim of this work was to determine the effect of chronic alcohol exposure on peripheral nerves in a nutritionally balanced rat model of alcoholism.

METHODS

Three different strains of adult male rats were pair-fed for 8 weeks with isocaloric liquid diets containing 0% or 37% ethanol. Nerve conduction studies (NCS) were performed. Peripheral nerve and muscle were examined histologically with morphometrics.

RESULTS

Ethanol exposure significantly slowed velocity in tibial and fibular nerves, but not in the plantar nerve in all 3 strains. Studies of the sciatic nerve revealed decreased fiber diameters and increased regenerative sprouts in peripheral nerves. There was muscle denervation of ethanol-exposed rats in all 3 strains.

CONCLUSIONS

Chronic ethanol exposure caused a polyneuropathy characterized by axonal degeneration despite adequate nutrition. These results suggest that ethanol exposure has direct neurotoxic effects on peripheral nerves. This model may be useful in understanding the underlying mechanism(s) of alcohol-related peripheral neuropathy.

Alcohol-related peripheral neuropathy: nutritional, toxic, or both?

Alcohol-related peripheral neuropathy (ALN) is a potentially debilitating complication of alcoholism that results in sensory, motor, and autonomic dysfunction. Unfortunately, ALN is rarely discussed as a specific disease entity in textbooks because it is widely assumed to primarily reflect consequences of nutritional deficiency. This hypothesis is largely based on observations first made over eight decades ago when it was demonstrated that thiamine deficiency (beriberi) neuropathy was clinically similar to ALN. In recent studies, failure of thiamine treatment to reverse ALN, together with new information demonstrating clinical and electrophysiological distinctions between ALN and nutritional deficiency neuropathies, suggests that alcohol itself may significantly predispose and enhance development of neuropathy in the appropriate clinical setting. We reviewed the evidence on both sides and conclude that ALN should be regarded as a toxic rather than nutritional neuropathy.

Alcohol consumption enhances antiretroviral painful peripheral neuropathy by mitochondrial mechanisms

A major dose-limiting side effect of human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) chemotherapies, such as the nucleoside reverse transcriptase inhibitors (NRTIs), is a small-fiber painful peripheral neuropathy, mediated by its mitochondrial toxicity. Co-morbid conditions may also contribute to this dose-limiting effect of HIV/AIDS treatment. Alcohol abuse, which alone also produces painful neuropathy, is one of the most important co-morbid risk factors for peripheral neuropathy in patients with HIV/AIDS. Despite the prevalence of this problem and its serious impact on the quality of life and continued therapy in HIV/AIDS patients, the mechanisms by which alcohol abuse exacerbates highly active antiretroviral therapy (HAART)-induced neuropathic pain has not been demonstrated. In this study, performed in rats, we investigated the cellular mechanism by which consumed alcohol impacts antiretroviral-induced neuropathic pain. NRTI 2',3'-dideoxycytidine (ddC; 50 mg/kg) neuropathy was mitochondrial-dependent and PKCε-independent, and alcohol-induced painful neuropathy was PKCε-dependent and mitochondrial-independent. At low doses, ddC (5 mg/kg) and alcohol (6.5% ethanol diet for 1 week), which alone do not affect nociception, together produce profound mechanical hyperalgesia. This hyperalgesia is mitochondrial-dependent but PKCε-independent. These experiments, which provide the first model for studying the impact of co-morbidity in painful neuropathy, support the clinical impression that alcohol consumption enhances HIV/AIDS therapy neuropathy, and provide evidence for a role of mitochondrial mechanisms underlying this interaction.

Neurological complications of alcohol usage

The relationships between alcohol usage and a number of neurological syndromes are reviewed. These are often complex and incompletely understood. Multiple rather than single factors are the rule rather than the exception. The correct diagnosis may be missed particularly where the aetiological role of alcohol is overlooked. Multiple diagnoses are not uncommon. Issues of differential diagnosis and diagnostic procedures are discussed. Management, including a number of its pitfalls, is outlined.

Histochemical and SEM evaluation of the neuromuscular junctions from alcoholic rats

In the present study morphological changes occurring in the neuromuscular junctions (NMJ) of the extensor digitorum longus (EDL) and soleus muscles from albino rats (Rattus norvegicus) submitted to experimental chronic alcoholism were evaluated. Seventy two male animals aged 4 months and weighing on average 400g were divided into three groups: control, alcoholic and isocaloric. Six rats from each group were anesthetized and sacrificed after 5, 10, 15 and 18 months. The NMJ did not show detectable morphological changes in either muscle after treatment when examined by light microscopy. With respect to the dimensions, statistical analysis demonstrated a tendency to a statistically significant treatment x time interaction for the length of soleus muscle NMJ. The ultrastructural study, however, revealed that the NMJ of the soleus muscle of animals submitted to 18 months of experimental alcoholism presented important morphological alterations. Characteristically, the NMJ of these muscles is located on an elevation on the surface of the muscle fiber, presenting a regular round, oval or elliptical shape and continuous and not very deep synaptic grooves. Approximately 30% of the NMJ of alcoholic rats are irregular in shape, with the sarcolemmal elevations typical of the synapse region being flattened on at least one side, with discontinuous synaptic grooves, and deep and punctiform contacts of the synaptic buds. These data suggest that, although skeletal muscle has a greater natural resistance against the direct or indirect effects of alcohol, some submicroscopic morphological alterations are detectable in the NMJ, especially in muscles with oxidative metabolism (soleus) following long periods of ingestion of alcohol.

Effect of ethanol on axonal transport of cholinergic enzymes in rat sciatic nerve

The aim of this study was to investigate whether the fast axonal transport of acetylcholinesterase (AChE) and the slow transport of choline acetyltransferase (ChAT) in the sciatic nerve of the rat are affected by chronic ethanol consumption or by associated nutritional deficiency. Adult rats drank ethanol (20% [vol./vol.]) instead of water for 20 weeks. Animals that consumed an isocaloric diet, representing a nutritional deficiency, received the same amount of food as ethanol-treated rats and water with sucrose replacing ethanol isocalorically. The control group received food and water ad libitum. Axonal transport was investigated by the stop-flow ligation technique as follows. After 20 weeks, the sciatic nerve was ligated for 24 h, and accumulation of AChE and ChAT was measured above and below the ligature. No significant differences in the accumulation of both enzymes were found above the ligature. However, the accumulation of AChE transported retrogradely below the nerve ligature was reduced by 60%, but only in ethanol-treated animals. Our study results seem to indicate that, under experimental conditions, (1) neither ethanol nor associated nutritional deficiency has any effect on anterograde axonal transport of AChE and ChAT and (2) the deficit in retrograde transport of AChE is due to the direct toxic effect of ethanol and probably precedes the axonal degeneration from the most distal portions of axons toward the cell body.

Reduced sensory and motor nerve conduction velocities in moderate drinkers

The mechanism responsible for peripheral nerve dysfunction in chronic alcoholism has not been fully elucidated either in terms of its relationship to the quantity of alcohol consumed or to nutritional status. As part of a series of studies to address these issues, the effects of moderate drinking (60-90 g ethanol per day) or heavy drinking (> 100 g ethanol per day) on peripheral nervous function and thiamine status was measured in 73 patients admitted to a detoxification unit. Electromyographic evaluation revealed significant reductions in median and ulnar sensory and motor nerve conduction velocities in both moderate drinkers (n = 30) and heavy drinkers (n = 43) compared to age-matched controls. Twelve moderate drinkers and 25 heavy drinkers manifested clinical neurological signs of peripheral neuropathy. Thiamine deficiency, as revealed by erythrocyte transketolase activation assay, was detected in two moderate drinkers and seven heavy drinkers but was not significantly correlated with electromyographic alterations with the exception of ulnar nerves. These findings provide evidence for significant early peripheral nerve dysfunction in moderate drinkers and a possible contributory role of thiamine deficiency to the ulnar nerve conduction deficits. Whether deficits in other water-soluble vitamins or a direct neurotoxic effect of ethanol are implicated in alcoholic peripheral neuropathy awaits further studies.

Vibrameter testing facilitates the diagnosis of uremic and alcoholic polyneuropathy

The diagnostic sensitivity of Vibrameter and tuning fork examination towards uremic and alcoholic neuropathy was tested in 75 patients. In 40 uremic and 35 alcoholic patients, we compared the sensitivity of neurological examination, nerve conduction studies (NCS) and vibration thresholds assessed at the malleoli by means of Vibrameter and scaled tuning fork. Vibrameter results were correlated with NCS. Polyneuropathy was diagnosed in 52 patients, but in 16 patients diagnosis depended upon inclusion of Vibrameter testing in the examination protocol. In uremic patients, Vibrameter (47.5%) showed abnormalities as often as NCS (45%), and more often than clinical (32.5%) or tuning fork examination (2.5%). In alcoholic patients, Vibrameter revealed abnormalities more often (60%) than NCS (34.3%) or tuning fork (14.3%). Correlations between NCS and vibratory thresholds were low (-0.52 < or = Rs < or = -0.35). Vibrameter studies are far more sensitive than tuning fork tests. The technique complements NCS and refines the diagnosis of uremic and alcoholic neuropathies.

Effects of alcohol feeding on synthesis and secretion of apolipoproteins by regenerating rat sciatic nerve

The amounts of apolipoprotein (apo) E and A1 released into the culture medium were examined in the regenerating nerves distal to a crush site following chronic alcohol feeding. Cultured minced segments of regenerating nerves taken from rats fed an alcohol-containing liquid diet for 5 weeks released only 50% of apoE but nearly 200% of apoA1 when compared with rats pair-fed with a control diet. The extent of decrease in medium apoE corresponded to the decrease of apoE mRNA in the nerve. Thus, chronic alcohol ingestion affects apoE synthesis of regenerating nerves by changing its mRNA level. On the other hand, apoA1 mRNA remained undetectable in regenerating and intact nerves whether the rats were fed alcohol or not. Furthermore, the amount of apoA1 released by the regenerating nerve into the culture medium was not significantly larger than that present in the nerve tissue prior to incubation. Therefore, it is most likely that apoA1 released by the injured nerve originated from the bloodstream and the increase in apoA1 content seen in the crushed nerve of alcohol-fed rats is due to an enhanced permeability of the nerve-blood barrier. Since the burst of apolipoproteins in the injured nerve is likely to play a role in nerve regeneration, the perturbation of apolipoprotein contents in regenerating nerves by chronic alcohol consumption may contribute to the pathogenesis of alcoholic neuropathy.

Pathological changes in peripheral nerves in experimental fetal alcohol syndrome

The peripheral nerve pathology is described in experimental fetal alcohol syndrome. The marked retraction and shrinkage of axons with vacuolar spaces in the periaxonal area are the striking features. The direct toxicity of ethanol or its metabolites on the nerve fibers is considered to be the cause for pathological changes. Additional biochemical factors, pyridoxal phosphate dependent enzyme-depletion in the genesis of nerve damage, is proposed.

Nervous system damage and nutritional factors in chronic alcoholics

Dietary habits in 45 chronic alcoholics were assessed by the dietary history method, and plasma albumin and serum transferrin. These variables as well as clinical findings did not indicate general malnutrition, but a moderate deficiency in folate intake was found. There was no correlation between the nutritional variables and central and peripheral nervous system function investigated by neuroradiological, neuropsychological, and neurophysiological methods. Transketolase and thiamine-pyrophosphate effects were measured in a subgroup of alcoholics and compared to a control group. No differences were found and there was no correlation to central nervous system impairment. These findings do not support the hypothesis that nervous system damage found in chronic alcoholics is of nutritional etiology.

Decreased axonal transport in rat nerve following acute and chronic ethanol exposure

The axonal transport system, which supplies essential proteins and other cellular components to the distal portions of peripheral nerve axons, has been postulated to be the primary site of vulnerability inducing the peripheral neuropathies associated with neurotoxin exposure. Axonal transport was examined in normal rat dorsal root ganglia-sciatic nerve preparations incubated 28 hours in vitro in the presence of 79, 198 or 395 mg% ethanol. Exposure of the nerves to 395 mg% ethanol significantly reduced the accumulation of radiolabeled protein by 70%. Also, groups of rats were pair-fed an ethanol or isocaloric control diet for 9, 16 or 28 weeks. In vitro axonal transport was found to be unchanged in nerves of rats fed the ethanol diet for 9 weeks, but was significantly reduced 44% after 16 weeks and 47% after 28 weeks of ethanol feeding. These results suggest that interference with the axonal transport machinery by ethanol or perhaps acetaldehyde, its primary metabolite, may lead to the development of alcoholic peripheral neuropathy.

Ethanol and polyneuropathy

Two groups of alcoholics (30 patients each)--identified by the MALT score--were examined. Clinical and laboratory investigations showed no connection between thiamine, riboflavin, or Vitamin B6 deficiency and development of the polyneuropathy. Neither the polyneuropathy nor the diminished sensory conduction velocity were related to malnutrition. The relation between the duration of alcoholism and symptoms of polyneuropathy was highly significant in one group. The neurotoxicity of ethanol was confirmed in an experiment with rats.

Alcoholic polyneuropathy

Alcoholic polyneuropathy is a common disorder, characterized by nonspecific clinical, electromyographic, and pathologic features. Nerve conduction studies and needle electromyography disclose findings consistent with a generalized, sensorimotor, axonal degenerative, polyneuropathy. Alcoholic polyneuropathy may be suspected when such findings occur in the setting of long-standing alcoholism and malnutrition. The lack of specific diagnostic criteria for alcoholic polyneuropathy requires that other potential etiologies be excluded before that diagnosis is made. The institution of a nutritionally-balanced diet constitutes the principal therapy for alcoholic polyneuropathy, however, significant improvement following such therapy is not frequently seen.

Peripheral neuropathy, cerebral atrophy, and intellectual impairment in chronic alcoholics

Peripheral neuropathy, cerebral atrophy, and intellectual impairment was investigated in 46 males with alcoholic nervous system damage. An overall correlation was found between peripheral neuropathy and cerebral atrophy and between several of the individual neurophysiological and neuroradiological variables examined. There was also a correlation between cerebral atrophy and intellectual impairment. The findings support the view that alcohol in itself is toxic to central and peripheral nervous tissues, although a dose-response dependence could not be established.

Alcoholic neuropathy and hepatopathy in mice. An experimental study

Seventeen young adult C57BL male mice were given 15% (w/v) solution of ethanol as their sole drinking fluid for seven to nine months. C57BL male mice given regular drinking water were used as controls. After decapitation samples from the livers and the sciatic nerves of the mice were processed for electron microscopy and morphometry. The ultrastructural analysis revealed slight alterations in the nerves of the ethanol-exposed mice. The changes were mostly in the Schwann cells. Pathological Schwann cell-axon relationships were also more abundant in the ethanol-exposed mice. The thickness distribution of the myelinated nerve fibers was similar in the exposed and the control mice. The transverse-sectional area of hepatocytes was greater in the mice on ethanol than in the controls. The volume density of lipid vacuoles of the liver cells was significantly increased in the mice treated with ethanol (p less than 0.001). The hepatic changes indicate a significant effect of ethanol on the liver. The findings suggest that, in mice, chronic peroral treatment with ethanol can produce slight changes suggesting peripheral neuropathy together with fatty metamorphosis of the liver.

The neurotoxicity of ethanol

Alterations in nervous system functioning following acute and chronic ethanol exposure have been studied in a great number of experimental investigations. Results from many of these investigations can be difficult to interpret, particularly since a variety of techniques and exposure models are employed. This review emphasizes those studies which, in the opinion of the author, fit into a pattern where results from studying one function of the nervous system is in accordance with results from studying another. Thus, the fluidizing effect of ethanol on the neuronal membrane - an effect which ethanol shares with anaesthetics - leads to a change in protein function which in turn affects ion transport such as Na+ and Ca++ across the membrane due to changes in the ion channels. Cation influx is probably directly coupled to neurotransmitter release which is in agreement with the finding that ethanol exposure results in inhibition of Na+ and Ca++ current as well as acetylcholine release. The sensitization of the dopaminergic system after ethanol exposure may also be related to the changes in cation flux, and the changes in this system probably play a crucial rôle in the development of tolerance and withdrawal symptoms. Other aspects such as impairment of protein synthesis, altered GABA function of impairment of neuron excitability and conduction are more difficult to place in proper perspective. The rôle of acetaldehyde in acute as well as chronic ethanol intoxication also remains a controversy. These may, however, be secondary phenomena to primary changes in different part of the nervous system not necessarily important in the clinical situation. Behavioural and anatomical studies particularly from recent years have shown that experimental animals develop memory disturbances following chronic exposure even when kept on sufficient diet. These findings argue strongly for a direct toxic effect of ethanol, and are furthermore compatible with behavioural changes in chronic alcoholics, dominated by memory impairment. Since it has been argued that the cholinergic system plays a significant rôle for memory function, a possible explanation for some of the psychological and anatomical deficits caused by ethanol is thus the changes in the function of the cholinergic system particularly in the hippocampal regions.

Acute effects of alcohol on the peripheral nerves in diabetic polyneuropathy: a clinical and neurophysiological study

Acute effects of alcohol on the peripheral nerves of seven patients with diabetic polyneuropathy and 13 healthy subjects were examined neurophysiologically. Ethanol (1 g/kg) caused a slight increase in skin temperature and motor conduction velocity in both groups. Motor distal latencies decreased in the healthy subjects, but increased among polyneuropathic patients after the consumption of alcohol. Diabetic nerves appear most susceptible to the acute effects of alcohol.

The combined toxicity of technical grade xylene and ethanol in the rat

1. Inhalation exposure to xylene of technical grade (300 p.p.m. in air, 6 h a day, 5 days a week, up to 18 weeks) enhanced the overall mono-oxygenation reactions (7-ethoxycoumarin O-deethylase and 2,5-diphenyloxazole hydroxylase( as well as the UDP-glucuronyltransferase activity in rat liver microsomes. 2. The simultaneous ingestion of aqueous 15-20% ethanol as drinking fluid increased the cytochrome P-450 concn. and the mono-oxygenation activity even more than the xylene exposure alone. 3. Xylene-ethanol treatment resulted in additive or less than additive effects on the measured hepatic enzyme activities. 4. Renal ethoxycoumarin deethylase activity was enhanced both by ethanol ingestion and by xylene inhalation, and the response was additive after the combined exposure. 5. Liver histology revealed that even though the xylene exposure alone did not produce detectable liver damage, the xylene-ethanol treatment produced more severe liver damage than did ethanol ingestion alone.

Behavioural and glial cell effects of inhalation exposure to styrene vapour with special reference to interactions of simultaneous peroral ethanol intake

Male Wistar rats were exposed to 300 p.p.m. of styrene vapour with simultaneous ethanol ingestion for 4 to 17 weeks. The effects on behaviour were analyzed after 4, 9 and 13 weeks of the experiment. The most manifest behavioural effects were found in rats exposed to the combination, and the changes included increased preening time at the 4th week and increased ambulation and rearing at the end of the exposure. The ethanol ingestion affected also the accumulation of the solvent burden by delaying the peak solvent concentration in the perirenal fat to the 8th week of exposure. The fat solvent concentration did not differ from each other in the two groups at the end of the experiment, and they were similar as compared the concentration found in phenobarbital-pretreated rats exposed for reference. The styrene exposure had almost no effects on cerebral glial cells whereas ethanol induced unexpectedly increased protein destruction in them throughout the experiment. Co-exposure to ethanol and styrene decreased the magnitude of protein destruction in the glial cells. Withdrawal of the rats after an 8-week exposure showed that the styrene effects were largely abolished in two weeks of exposure-free period as analyzed by the determination of brain RNA and acid proteinase activity. Brain RNA was lower than control after two weeks of ethanol deprivation. The present data indicate that marked metabolic interactions between ethanol and styrene take place in agreement with experience on other similar solvent combinations.

Neurochemical and behavioural effects of extended exposure to isopropanol vapour with simultaneous ethanol intake

Exposure of male Wistar rats to 12.3 mumol/l (300 ppm) isopropanol vapour for 5-21 weeks, 5 days a week for 6 h daily with a simultaneous ethanol administration in drinking water (5% v/v) caused a significant increase in isopropanol removal as assessed by blood isopropanol and acetone determinations. Ethanol treatment caused a marked synergistic effect during early exposure. Neurochemical studies revealed decreased superoxide dismutase and azoreductase activities at the end of the exposure whereas increased protein degradation was found in glial cells isolated from ethanol-fed rats throughout the experiment. Analyses of spinal cord axon lipid composition showed increases in cholesterol content in relation to lipid phosphorus in animals exposed to isopropanol or to the isopropanol and ethanol combination. Behavioural tests indicated minor effects on emotional reactivity from the 10th week onwards with isopropanol exposure whereas caffeine-stimulated activity was augmented only in rats ingesting ethanol. Co-exposure to isopropanol vapour abolished the increased excitability. The data indicate that marked metabolic and functional adaptation towards the small-molecular-weight alcohols takes place at moderate dose levels.

Peripheral neuropathy and myopathy. An experimental study of rats on alcohol and variable dietary thiamine

The effects of variable dietary thiamine concentrations (deficient, normal, surplus) on the development of alcoholic neuromyopathy in rats exposed for 36 weeks to 10-25% (v/v) ethanol or water (control group) as the sole drinking fluid were studied by histological and electrophysiological methods. Abnormalities in the structure of the sciatic nerve (phagocytosis, myelin abnormalities, increase in nonspecific cholinesterase activity) and tibial muscles (angular atrophic fibers, group atrophy, fibre necrosis) developed more frequently in animals on diets deficient in thiamine than in animals on diets with normal or surplus thiamine, and more frequently in animals drinking alcohol and water than in those drinking water alone. No differences were observed between the different groups in the number of perivascular sympathetic nerves, in the motor nerve conduction velocities and in the muscle fibrillation potentials. Thus, thiamine deficiency, established as a significant reduction of red blood cell transketolase activity, seems to have a deleterious effect on the peripheral nerves and muscles. The effect is enhanced by the simultaneous consumption of ethyl alcohol.

Neurochemical and behavioural effects of long-term intermittent inhalation of xylene vapour and simultaneous ethanol intake

Two-month-old male Wistar rats were exposed to 300 p.p.m. of xylene vapour with simultaneous ethanol ingestion for 5 to 18 weeks. Neurochemical effects of mere vapour inhalation included an increase in microsomal superoxide dismutase activity in brain at the end of the experiment. Concomitant ethanol ingestion added significantly to the xylene-induced effects by causing increased proteolysis at the 9th and 14th week of exposure whereas cerebral superoxide dismutase failed to increase in these animals. Preening frequency decreased transiently in ethanol and in xylene groups at 6 and 9 to 12 weeks, respectively, whereas increased ambulation occurred only in the xylene--ethanol group after 12 and 14 weeks of exposure. The behavioural effects were therefore different in the combined exposure, and our biochemical and behavioural observations may point at significant interaction of both solvents although the biochemical mechanisms remain largely unexplained.

Animal models of alcoholic neuropathy: morphologic, electrophysiologic, and biochemical findings

A chronic high alcohol intake was induced in rats through the use of two procedures: the schedule-induced polydipsia technique and the liquid diet technique. Rats consumed 11-12 g of ethanol per kilogram body weight per day for 16 to 18 weeks. Morphologic evidence of a mild distal axonal neuropathy in the ventral caudal nerve was proposed. The red blood cell transketolase levels were normal, indicating that the rats were not deficient in thiamine and suggesting that the axonal degeneration was due to the direct toxic effect of alcohol. Axonal transport studies demonstrated a significant increase in the amount of acetylcholinesterase transported in an orthograde direction in the sciatic nerves of alcohol-exposed rats, and indicated no change in the transport of choline acetyltransferase or in the specific binding of colchicine by neurotubulin.

Biochemical and toxicological effects of short-term, intermittent xylene inhalation exposure and combined ethanol intake

Intermittent inhalation of 300 ppm of xylene vapour 6 h daily for 2 weeks caused a marked accumulation of the solvent in the perirenal fat. Simultaneous ethanol ingestion reduced the solvent load significantly although the perirenal xylene concentration increased in both test groups between the first and second week of exposure. Xylene inhalation enhanced hepatic and renal ethoxycoumarin 0-deethylase activity about 1.5-fold. The combination of inhaled xylene and peroral ethanol showed a markedly potentiated effect on microsomal ethoxycoumarin 0-deethylase activity especially in the kidneys. The enhanced monooxygenase activity was compatible with the decreased body solvent burden. Therefore, simultaneous ethanol intake might significantly modify the toxicological hazard in xylene exposure. Slightly increased proteolysis was detected in brain of animals in the xylene-ethanol experiment after the second week. Brain RNA content decreased after 2 weeks of exposure in the ethanol consuming animals. Xylene inhalation enhanced cerebral DT-diaphorase activity in both groups after 2 weeks of exposure. Ethanol intake also potentiated the behavioural effects caused by the solvent inhalation.

Myopathy associated with chronic alcohol drinking. Histological and electrophysiological study

Muscles of the lower legs of rats given 25% ethanol in water ad libitum for up to 9.5 months were studied using histological, histochemical and electrophysiological techniques. Ethyl alcohol was substituted for about 20% of the total calorific input of the animals. The observations were compared with the structure of the gastrocnemius muscle of five alcoholics with clinical neuropathy. Fibrillation potentials and angulated atrophic fibers were observed in the muscles of animals on alcohol for 9.5 months. No fiber type grouping was present. There was also phagocytosis of the muscle fibers and changes in their internal structure, as reflected by the distribution of NADH-diaphorase. The observed muscle changes in the alcoholics and those in the experimental animals on alcohol differed mainly quantitatively, the only exception being the presence of fiber type grouping in the biopsies from the alcoholics.