Evoked potential changes during ethanol withdrawal in rats

The structural effects of Vitamin A deficiency on biological macromolecules due to ethanol consumption and withdrawal: An FTIR study with chemometrics

The structural effects of vitamin A-deficiency were examined on the molecular profiles of biomolecules of male rat hippocampus during prolonged ethanol intake/withdrawal using FT-IR spectroscopy coupled with chemometrics. Liquid ethanol diet with/without vitamin A was maintained to adult rats for 3-months. The rats were decapitated at different ethanol withdrawal times and FT-IR spectra were obtained. Ethanol consumption/withdrawal produced significant changes in proteins' conformations, while having insignificant structural effects on lipids. In vitamin A deficiency, ethanol produced structural changes in lipids by lipid ordering especially in the early-ethanol withdrawal. Furthermore, an increase in lipid and protein content, saturated/unsaturated lipid ratio, a decrease in nucleic acids content and decrease in membrane fluidity were observed. These changes were less severe in the presence of Vitamin A. This study is clinically important for individuals with vitamin A deficiency because they have to be more cautious when consuming alcohol to protect themselves from cognitive dysfunctions.

Modulation of responses to visual stimulus onset and offset by chronic alcohol consumption and withdrawal in the rat visual cortex and lateral geniculate nucleus

In the visual system, chronic alcohol consumption and subsequent abstinence strongly modulate processing of sensory information, which could interfere with the actions in our daily lives. Although previous studies showed histological and electrophysiological changes in the retina and visual cortex during chronic alcohol consumption and abstinence, there is still a lack of information related to the effect of alcohol on: 1) different stages of visual information processing; and 2) responses of stimulus onset (ON) and offset (OFF). In order to answer these questions, we recorded visual evoked potentials (VEPs), elicited by onset and offset of a 500-ms stimulus, following long-term alcohol consumption (8 weeks) and abstinence (3 weeks) in freely moving Wistar rats. Latency and amplitude of five components in the visual cortex (N1_VC, P2_VC, N2_VC, P3_VC, N3_VC) and three components in the lateral geniculate nucleus (P1_LGN, N1_LGN, P2_LGN) were analyzed. The results showed that long-term chronic alcohol consumption and abstinence have a strong long-term and, in some cases, irreversible impact on visual information processing. Both of these conditions modulate only the last stage of stimulus onset processing at the level of the visual cortex, but not at the level of the lateral geniculate body. Response to the stimulus offset is more susceptible to the effect of alcohol consumption and/or abstinence and is modulated at both the visual cortex and lateral geniculate nucleus levels. This modulation at different stages of the information processing chain can result in inaccurate processing of visual stimuli parameters and can lead to changes in perception of stimulus duration and intensity.

The P300 event-related brain potential as a neurobiological endophenotype for substance use disorders: a meta-analytic investigation

Endophenotypes are intermediate phenotypes on the putative causal pathway from genotype to phenotype and can aid in discovering the genetic etiology of a disorder. There are currently very few suitable endophenotypes available for substance use disorders (SUD). The amplitude of the P300 event-related brain potential is a possible candidate. The present study determined whether the P300 amplitude fulfils two fundamental criteria for an endophenotype: (1) an association with the disorder (disease marker), and (2) presence in unaffected biological relatives of those who have the disorder (vulnerability marker). For this purpose, two separate meta-analyses were performed. Meta-analysis 1 investigated the P300 amplitude in relation to SUD in 39 studies and Meta-analysis 2 investigated P300 amplitude in relation to a family history (FH+) of SUD in 35 studies. The findings indicate that a reduced P300 amplitude is significantly associated with SUD (d=0.51) and, though to a lesser extent, with a FH+ of SUD (d=0.28). As a disease maker, the association between reduced P300 amplitude and SUD is significantly larger for participants that were exclusively recruited from treatment facilities (d=0.67) than by other methods (i.e., community samples and family studies; d=0.45 and 0.32, respectively), and larger for abstinent SUD patients (d=0.71) than for current substance users (d=0.37). Furthermore, in contrast to FH+ males, a P300 amplitude reduction seems not to be present in FH+ females (d=-0.07). Taken together, these results suggest that P300 amplitude reduction can be both a useful disease and vulnerability marker and is a promising neurobiological endophenotype for SUD, though only in males. Implications and future directions are discussed.

What is inherited in the predisposition toward alcoholism? A proposed model

BACKGROUND

The etiological factors associated with the predisposition to develop alcohol dependence remain largely unknown. In recent years, neurophysiological anomalies have been identified in young and adult offspring of alcoholic probands. These neuroelectric features have been replicated in several laboratories across many different countries and are observed in male and female alcoholics and some of their relatives and offspring. Moreover, these electrophysiological abnormalities are heritable and predictive of future alcohol abuse or dependence.

METHODS

A model is presented which hypothesizes that the genetic predisposition to develop alcoholism involves an initial state of central nervous system (CNS) disinhibition/hyperexcitability. We propose that the event-related brain potential (ERP) anomalies reflect CNS disinhibition. This homeostatic imbalance results in excess levels of CNS excitability which are temporarily alleviated by the ingestion of alcohol. It is hypothesized that this hyperexcitability is heritable, and is critically involved in the predisposition toward alcoholism and the development of dependence. A brief review of the relevant literature is presented.

RESULTS

Neurophysiological, neurochemical, and genetic evidence support the proposed model. In addition, strikingly similar observations between animal research and the human condition are identified. Finally, it is asserted that the proposed model is primarily biological in nature, and therefore does not account for the entire clinical variance.

CONCLUSION

A putative CNS homeostatic imbalance is noted as a critical state of hyperexcitability. This hyperexcitability represents a parsimonious model of what is inherited in the predisposition to develop alcoholism. It is our hope that this model will have heuristic value, resulting in the elucidation of etiological factors involved in alcohol dependence.

Alterations in cortical visual evoked response following ethanol feeding in adult rats

A study was performed on the visual-evoked response (VER) in adult rats that were given an ethanol containing liquid diet for 2 months and examined directly after the exposure period or subjected to a gradual decrease in ethanol over 3 days and total abstinence for 1 week. Control rats showed a first negative peak (N1) directly following the first positive peak (P1). In ethanol-exposed rats examined without withdrawal, the VER showed an increase in onset latency and a marked distorsion of the N1 region. The existing N1 potential was very sensitive to high-frequency stimulation. The alterations were partly normalized 1 week after withdrawal. There was no increase in latency to onset of the response or to P1. There remained an increase of latency and a reduced relative amplitude upon high-frequency stimulation of the N1 peak in ethanol-exposed rats compared with controls. The mechanisms underlying the changes in the cortical potentials are not clear, but they may be related to the cholinergic, glutamatergic/NMDA and/or noradrenergic cortical systems. The lack of persistent changes in onset and P1 latency may be related to the circumstance that the retinogeniculate impulses are transmitted over glutamatergic kainate receptors, which are relatively resistant to ethanol.

Late auditory evoked potentials in alcoholics. Identifying those with a history of epileptic seizures during withdrawal

The N1-P2 wave of the auditory evoked potential was studied in 19 alcoholics, six of whom had withdrawal seizures on previous admissions. The recordings were made at 1 and 5 days after cessation of drinking. Eight nonalcoholic volunteers were used as controls. The latencies of N1 and P2 were slightly prolonged in alcoholics, but during the detoxification period they frequently shortened (p less than 0.05), occasionally attaining the values of the controls. One day after withdrawal, the amplitude of N1-P2 was consistently reduced in the alcoholics compared to the controls (p less than 0.05 and p less than 0.01), but higher in alcoholics with a seizure history compared to alcoholics without seizures (p less than 0.05 and p less than 0.001). Five days after cessation of drinking, the amplitude in the alcoholic groups always increased from the admission values (p less than 0.05 and p less than 0.01). By that time, the alcoholics with a history of withdrawal seizures had significantly (p less than 0.05 and p less than 0.01) higher amplitudes than those of the controls or the alcoholics without seizures. Large N1-P2 amplitude during alcohol withdrawal may reflect increased cerebral excitability and contribute to the identification of alcoholics with high risk for withdrawal seizures.

EEG and ERP response to chronic ethanol exposure in rats

Chronic ethanol exposure has been described in humans to produce a series of long and short term electrophysiological consequences. Interpretation of the electrophysiological findings in human subjects, however, is made difficult due to concomitant factors, such as nutritional status, premorbid functioning and differences in genetic susceptibility to the effects of ethanol. In the present study, electroencephalograms (EEGs) and auditory event related potentials (ERPs) were utilized to explore the short and longer term effects of chronic ethanol exposure in rats. Rats were continuously exposed to ethanol vapors for a period for 1 month. This treatment produced a mean blood ethanol level of 178 +/- 13.86 mg%. EEGs and ERPs were subsequently collected at 10 min, 24 h, and 2 weeks following termination of ethanol exposure. Significant changes in the EEGs and ERPs of these rats could be demonstrated. EEG amplitude increases, as quantified by spectral analysis, were most prominent at the 24 h time period, perhaps reflecting a state of "rebound excitability". EEG responses were normalized in ethanol-treated rats by 2 weeks post-withdrawal. In contrast, reductions in the N1 and P2 amplitudes of the rat ERPs were prominent after chronic ethanol exposure and following 2 weeks withdrawal, suggesting that ethanol may produce some longer term effects on response to ERP stimuli. Taken together, these studies suggest that ethanol may produce differential effects on EEG and ERPs and that this model may provide a useful substrate for the evaluation of the mechanisms underlying the effects of chronic ethanol exposure.

Ethanol withdrawal increases sensory responsiveness of single somatosensory cortical neurons in the awake, behaving rat

This study investigated the effects of ethanol withdrawal on sensory responses of single neurons recorded in the somatosensory (SI) cortex of awake, behaving, ethanol-dependent rats. Eleven rats were fed an ethanol-containing liquid diet for 90-120 days, while 11 weight-matched controls were pair-fed an equivalent sucrose containing diet to equalize caloric intake. Single SI cortical neurons in the chronically treated rats were recorded continuously over several hours after withdrawal from ethanol, and after reintoxication induced by intraperitoneal injection of 10% (v/v) ethanol solution. Intoxication and withdrawal related changes in sensory responsiveness of these neurons were quantitatively measured by stimulating through electrodes chronically implanted under the skin of the forepaw. Sensory response histograms constructed from these stimuli showed a characteristic pattern, typically consisting of two early excitatory peaks (E1a and E1b), followed by an inhibition (I1), and in some neurons, a late excitatory response (E2). As withdrawal advanced, the sensory response histograms exhibited marked increases in the magnitudes of the E1a, I1, and E2 responses, coupled with a reduced spontaneous discharge rate. These changes are similar to, but quantitatively greater than, those which have previously been observed in normal and control rats during "immobile arousal" behaviors, which can be evoked when an experimenter holds the animals still, producing an immobile "aversive arousal." In withdrawing animals this same "holding" manipulation tended to markedly exacerbate and accelerate behavioral and neurophysiological signs of withdrawal. By contrast, the same manipulations had little effect when carried out during light intoxication or early stages of withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of acute and chronic administration of ethanol on photic-evoked response in rats

The effect of acute and chronic administration of ethanol on photic-evoked response was studied in rats. Acute administration of ethanol (1-3 g/kg, i.p.) produced behavioural depression, EEG synchronization and a biphasic effect on the amplitude of the photic evoked responses (PER) recorded from the frontal cortex (FC) and optic cortex (OC), while a reduction in amplitude was observed in the midbrain reticular formation (MBRF). The amplitude of the averaged PER in the FC and OC was increased in chronic ethanol-treated rats, while in the MBRF, a reduction in amplitude was observed. Abrupt discontinuation of ethanol produced behavioural excitation and increase in amplitude of the averaged evoked responses recorded from the three brain areas studied. These observations suggest that the neural hyperexcitability that characterizes ethanol withdrawal may affect both cortical and subcortical structures.

Cellular immune functions, endorphins, and alcohol consumption in males

The effects of alcohol abuse on cellular immune functions were measured by various levels of alcohol use in adult men. Total lifelong abstainers were used as controls. Previous abusers, current abusers, and patients with alcoholic cirrhosis or pancreatitis were age-matched to controls. T-lymphocyte mitogenesis stimulated by phytohemagglutinin and concanavalin A was generally reduced in peripheral blood lymphocytes of current and previous alcohol consumers, although the decrease was not statistically significant. B-cell mitogenesis stimulated by pokeweed mitogen was not changed by previous alcohol consumption. The number of T-cells was not changed by either previous or current alcohol abuse. T-helper cells were significantly increased and T-suppressor cells increased only in the patients with alcoholic cirrhosis or pancreatitis. The percentage of T-lymphocytes with T-suppressor characteristics in controls was 27% while in alcoholic cirrhosis or pancreatitis subjects it was 16%. Plasma corticosteroid levels were significantly increased in people currently consuming alcohol (12.1 +/- 1.1 mg/dl) compared to controls (7.7 +/- 1.1). The corticosteroid levels were also higher in previous alcohol abusers although not statistically significant. Plasma endorphin levels were increased by severe alcohol abuse in the patients with cirrhosis or pancreatitis to 25.03 +/- 6.74 from 11.85 +/- 2.48 pg/ml in controls.

Acute effects of alcohol on photic evoked potentials of rats: lateral geniculate nucleus and reticular formation

This study examined the effects of ethanol on photic evoked potentials recorded from the dorsal lateral geniculate nucleus (LGN) and midbrain reticular formation (MRF) of chronically implanted albino rats. Animals were given intraperitoneal injections of saline, or of 0.5, 1.0, 1.5 or 2.5 g ethanol/kg body weight on separate days. Evoked potentials were recorded at 5, 20, 40 and 60 min following injection. An early positive component recorded from each structure was depressed in amplitude by only the 2.5 g/kg alcohol dose, while the succeeding negative component was depressed by both the 1.5 and 2.5 g/kg doses. Latencies of both early components in each structure were increased by the 1.5 and 2.5 g/kg alcohol doses. Alcohol doses of 1.0-2.5 g/kg depressed the amplitude of a later positive component in the LGN (latency of 78 msec), but latency was not altered. In contrast, a late positive component in the MRF (latency of 150 msec) was both decreased in amplitude and increased in latency by only the 2.5 g/kg dose. These results on subcortical structures are discussed in relation to alcohol's effects on cortical evoked potentials.

Changes of neurochemical and electrophysiological indices of rat brain under ethanol intoxication

It was found that acute ethanol intoxication caused an imbalance of the neurotransmitters in the CNS: accumulation of GABA and serotonin and depletion of catecholamines. Alcohol depression was characterized by suppression of the evoked potentials of the various rat brain structures. Under chronic ethanol intoxication of animals, relative stabilization of the electrophysiological indices of the rat brain activity was observed. This reflects the CNS adaptation to the constant ethanol presence in the blood. This state was also characterized by the relative stabilization of the serotonin system and by the increase of the catecholamine level. Withdrawal of ethanol after prolonged consumption caused accumulation of catecholamines in rat brain, depletion of serotonin and GABA, and increased excitability of the nervous structures. The changes of activity of the GABA- and monoaminergic systems are coupled to manifestation of symptoms of alcohol depression and convulsive reactions during ethanol withdrawal.

Changes in the rhesus monkey's EEG responses to ethanol during chronic exposure

This study was designated to document the changes in the CNS response to ethanol during chronic exposure in 5 male, 3.5--5.0 kg rhesus monkeys. Electrodes were implanted bilaterally into the amygdala, hippocampus and the calvarium over the frontal and temporal cortex. Ethanol or control solutions were administered intragastrically through indwelling cannulae. The 1.25 g/kg ethanol challenge dose was administered during EEG recordings. After one challenge dose, the animals received 60 days of chronic alcohol exposure (3.0 g/kg/day increasing to 8.0 g/kg/day). EEG was recorded every 10 days and analyzed by period analysis. Changes in the effect of the challenge dose were assessed by determining the percentage change of the EEG from pre-dose levels to selected times post-dose throughout the chronic alcohol exposure. The EEG response changed significantly during chronic alcohol treatment. Although each structure exhibited a slightly different pattern of change, the overall change was a shift from an excitatory response in the non-tolerant animal to an EEG slowing during chronic exposure. We suggest that such a change may be useful as a diagnostic marker for alcohol tolerance. In addition, the differential nature of the in vivo expression of alcohol tolerance in each brain area suggests that such analysis may provide a valuable tool for understanding the mechanism and expression of alcohol tolerance in the CNS.

Persistence of brain hyperexcitability following chronic alcohol exposure in rats

Eighteen hooded Long-Evans rats were implanted with monopolar electrodes for the purpose of recording visual evoked potentials (VEP's) at the following brain sites: visual cortex, reticular formation and thalamus. Baseline VEP's were obtained to flashes for all animals, and subsequently twelve rats were intubated daily with a progression of increasing quantities of 20% (V/V) alcohol (3-8 g/kg), while the remaining six rats received an equivalent amount of water in the same fashion. Beginning 4 1/2 hours after the last dose of intubated alcohol, withdrawal VEP's were sampled every half-hour up to 8 hours, and 24-27 hours postwithdrawal. All experimental animals manifested their greatest brain hyperexcitability at visual cortex, which peaked sharply between 7-8 hours after alcohol withdrawal. Following two weeks of abstinence, half of the experimental rats (N = 6) and half of the controls (N = 3) received an alcohol challenge dose (2 g/kg i.p.), while the remaining animals received the same challenge dose after five weeks. Marked hyperexcitability was observed in the two-week challenge dose animals that had been previously subjected to alcohol; no such increase in VEP amplitude was apparent for control rats. There is also some evidence of hyperexcitability after five weeks of abstinence from alcohol at visual cortex. The data indicates that the neurophysiological responses of post-addict rats to challenge doses of alcohol are readily distinguishable from those of naive animals, even five weeks after alcohol removal. Furthermore, alcohol seems to act differently at different sites of the brain.

Response suppression on a mixed schedule of reinforcement during alcohol withdrawal

Two groups of rats were maintained on a mixed fixed-ratio, fixed-interval schedule of food reinforcement until performance was stable. The animals were intubated daily with ascending doses of alcohol or water 30 min before each session, starting with 4.0 g/kg and increasing to the final dose of 8.0 g/kg. The results show that withdrawal from alcohol suppresses responding in all components of a mixed schedule and this suppression lasts approximately 14 hours. These results support previous reports which suggest that the duration of the behavioral aberrations produced by alcohol withdrawal are most severe 6 to 14 hours post-withdrawal.