The effects of alcohol on sensory evoked and spontaneous cerebral potentials in man

Effects of sleep deprivation on sleep homeostasis and restoration during methadone-maintenance: a [31]P MRS brain imaging study

Insomnia afflicts many individuals, but particularly those in chronic methadone treatment. Studies examining sleep deprivation (SD) have begun to identify sleep restoration processes involving brain bioenergetics. The technique ([31])P magnetic resonance spectroscopy (MRS) can measure brain changes in the high-energy phosphates: alpha-, beta-, and gamma-nucleoside triphosphate (NTP). In the present study, 21 methadone-maintained (MM) and 16 control participants underwent baseline (BL), SD (40 wakeful hours), recovery1 (RE1), and recovery2 (RE2) study nights. Polysomnographic sleep was recorded each night and ([31])P MRS brain scanning conducted each morning using a 4T MR scanner (dual-tuned proton/phosphorus head-coil). Interestingly, increases in total sleep time (TST) and sleep efficiency index (SEI) commonly associated with RE sleep were not apparent in MM participants. Analysis of methadone treatment duration revealed that the lack of RE sleep increases in TST and SEI was primarily exhibited by short-term MM participants (methadone <12 months), while RE sleep in long-term MM (methadone >12 months) participants was more comparable to control participants. Slow wave sleep increased during RE1, but there was no difference between MM and control participants. Spectral power analysis revealed that compared to control participants; MM participants had greater delta, theta, and alpha spectral power during BL and RE sleep. ([31])P MRS revealed that elevations in brain beta-NTP (a direct measure of ATP) following RE sleep were greater in MM compared to control participants. Results suggest that differences in sleep and brain chemistry during RE in MM participants may be reflective of a disruption in homeostatic sleep function.

Differential effects of acute alcohol on prepulse inhibition and event-related potentials in adolescent and adult Wistar rats

BACKGROUND

Previous studies have demonstrated that adolescent and adult rats show differential sensitivity to many of the acute effects of alcohol. We recently reported evidence of developmental differences in the effects of acute alcohol on the cortical electroencephalogram. However, it is unclear whether developmental differences are also observed in other neurophysiological and neurobehavioral measurements known to be sensitive to alcohol exposure. The present study determined the age-related effects of acute alcohol on behavioral and event-related potential (ERP) responses to acoustic startle (AS) and prepulse inhibition (PPI).

METHODS

Male adolescent and adult Wistar rats were implanted with cortical recording electrodes. The effects of acute alcohol (0.0, 0.75, and 1.5 g/kg) on behavioral and ERP responses to AS and PPI were assessed.

RESULTS

Acute alcohol (0.75 and 1.5 g/kg) significantly reduced the behavioral and electrophysiological response to AS in adolescent and adult rats. Both 0.75 and 1.5 g/kg alcohol significantly enhanced the behavioral response to PPI in adolescent, but not in adult rats. During prepulse + pulse trials, 1.5 g/kg alcohol significantly increased the N10 pulse response in the adolescent frontal cortex. Acute alcohol (0.75 and 1.5 g/kg) also increased the N1 ERP pulse response to prepulse stimuli in frontal and parietal cortices in adult rats, but not in adolescent rats.

CONCLUSIONS

These data suggest that alcohol's effect on behavioral and electrophysiological indices of AS do not differ between adults and adolescents whereas developmental stage does appear to significantly modify alcohol-influenced response to PPI.

Arousal-related P3a to novel auditory stimuli is abolished by a moderately low alcohol dose

Concurrent measures of event-related potentials (ERPs) and skin conductance responses were obtained in an auditory oddball task consisting of rare target, rare non-signal unique novel and frequent standard tones. Twelve right-handed male social drinkers participated in all four cells of the balanced placebo design in which effects of beverage and instructions as to the beverage content (expectancy) were independently manipulated. The beverage contained either juice only, or vodka mixed with juice in the ratio that successfully disguised the taste of alcohol and raised average peak blood-alcohol level to 0.045% (45 mg/dl). ERPs were sensitive to adverse effects of mild inebriation, whereas behavioural measures were not affected. Alcohol ingestion reliably increased N2 amplitude and reduced the late positive complex (LPC). A large, fronto-central P3a (280 ms latency) was recorded to novel sounds in the placebo condition, but only on the trials that also evoked electrodermal-orienting responses. Both novel and target stimuli evoked a posterior P3b (340 ms), which was independent of orienting. Alcohol selectively attenuated the P3a to novel sounds on trials with autonomic arousal. This evidence confirms the previously suggested distinction between the subcomponents of the LPC: P3a may be a central index of orienting to novel, task-irrelevant but potentially significant stimuli and is an important component of the arousal system. P3b does not have a clear relationship with arousal and may embody voluntary cognitive processing of rare task-related stimuli. Overall, these results indicate that alcohol affects multiple brain systems concerned with arousal, attentional processes and cognitive-autonomic integration.

Reduction in BOLD fMRI response to primary visual stimulation following alcohol ingestion

The physiology of alcohol's effects on brain function is poorly understood. Emission tomographic imaging has revealed both acute and chronic alterations in resting cerebral hemodynamics and metabolism following alcohol ingestion. However, cerebral functional integrity under these conditions has received less attention. Functional magnetic resonance imaging (fMRI) offers a non-invasive method for assessing brain functional activation. In order to assess its utility for studying the effect of alcohol on brain function, we performed fMRI with photic stimulation before and after administration of either 0.7 mg/kg alcohol (N = 12) or placebo (N = 5), resulting in peak breath alcohol levels averaging 0.069 g/dl. We found that the amplitude of visual cortical activation in response to photic stimulation was significantly reduced by approximately 33% following alcohol administration (4.0 +/- 1.7% vs. 2.7 +/- 1.3%, P = 0.02), but not following placebo (4.2 +/- 1.5% vs. 4.1 +/- 1.4%, P = 0.7). The results also suggest that the baseline right hemispheric predominance of activation in response to photic stimulation may be reduced following alcohol, suggesting a greater effect on the right hemisphere, consistent with previous studies and alcohol's known effects on visuospatial processing. In addition, through the course of each activation session, there was a progressive reduction in response following alcohol. These data demonstrate that the cerebral effects of alcohol intoxication can be studied with fMRI, and that the effects on brain function of even moderate alcohol intoxication may be widespread, may be lateralized, and may include the visual system.

Auditory P300 in young alcoholics: regional response characteristics

An auditory oddball paradigm was used to record the P300 component of the event-related potential (ERP) in a group of medication-free, chronic male alcoholics (n = 51, mean = 32.2) and a control group (n = 25, mean = 27.2). Each subject received a binaurally presented series of high (1600-Hz)- and low (600-Hz)-frequency tones. The designation of the rare tone (0.125 probability) was alternated across subjects. When the subject detected the rare tone, he made a button press as quickly as possible to record his reaction time. Scalp recordings using the entire 10/20 System, as well as interpolated placements, were made from 31 electrodes. For purposes of statistical analyses, five regional electrode groups were created: F (frontal), C (central), P (parietal), O (occipital), and T (temporal). The results of MANOVA indicated that control P300 amplitudes were significantly greater than those of the alcoholics in all five regions, whereas there were no P300 latency differences between groups in any region. Regional response differences between the groups were also compared with measures of surface energy (SE) (Wang et al., 1994). SE is a recently developed, reference-free global field measure that uses the entire scalp potential field and treats potentials at different positions differently. SE was significantly reduced in the alcoholics compared with the controls in both the C (p < 0.0003) and P (p < 0.0006) regions, although there were no differences in its distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of ethanol on EEG activity in males at risk for alcoholism

The present investigation examined the effects of placebo (P), low dose (LD) and high dose (HD) ethanol on EEG activity in two groups of males. One group consisted of individuals at high risk for the development of alcoholism (HR, N = 21) while the other consisted of matched, low risk (LR, N = 21) controls. Only one condition (P, LD or HD) was presented each day and condition order was randomized. For each subject, both blood alcohol level(s) (BAL) measured via breathalyzer and EEG activity, using the entire 10/20 international system, were recorded prior to and at intervals of 35, 70, 105 and 140 min after P, LD or HD administration. The Fast Fourier Transform (FFT) was used to calculate power spectral densities (PSD). Measures of relative area under the power spectral curve were obtained for each of the following frequency bands: slow alpha (SA, 7.5-10 Hz), fast alpha (FA, 10.5-13.0 Hz), slow beta (SB, 13.5-19.5 Hz) and fast beta (FB, 20-26 Hz) at electrodes: F3, F4, C3, C4, P3, P4, O1 and O2. The results of repeated measures MANOVA conducted on the normalized values of relative areas revealed that at each electrode examined, ethanol elicited significant changes only in SA activity. Risk group differences in SA activity were observed only at electrodes F3, F4 and P4. These differences were the consequence of differential ethanol effects rather than differences in baseline SA levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Retention of orienting reaction habituation in chronic alcoholics

A polygraphic study on resistance to habituation of the somatic (EMG), autonomic (finger plethysmogram, galvanic skin reaction, respiration) and EEG (acoustic-evoked potential and EEG-blocking reaction) components of the orienting reaction, elicited by a repetitive auditory stimulus during successive (weekly) sessions was performed in 67 chronic alcoholics and in 70 matched normal subjects (control group). The study showed significant retention disturbances of orienting reaction habituation (i.e., of learning), or the "saving" of stimulations, achieved from one session to the other to obtain the habituation criterion, the savings being less in alcoholics than in control subjects. The severity of habituation retention disturbances depended on patients' ages, types of alcoholism, alcohol consumption intensity and chronicity, as well as the type of resting EEG.

ERP responses to ethanol and diazepam administration in squirrel monkeys

The effects of oral administration of two doses of ethanol (0.75 and 1.5 g/kg) and a single dose of diazepam (2.5 mg/kg) on electrophysiological responses to an event related potential (ERP) paradigm were investigated in the squirrel monkey Saimiri Sciureus. A passive auditory "oddball plus novel" tone sequence was utilized to elicit N1, P2, N2, and P3-like components which resembled waveforms obtained from human subjects under the same conditions. Ethanol at both doses was found to produce a significant decrease in the amplitude of the N1 component. The higher ethanol dose also produced a significant decrease in the amplitude of the P3-like component. Ethanol at both doses was observed to produce significant increases in the variability of the amplitude of these components as measured from trial to trial. Diazepam, like ethanol, also induced a significant decrease in the N1 component of the ERP but did not affect the later waves. These results suggest that ERPs can reliably assess the electrophysiological actions of ethanol in monkeys.

Neurophysiological approaches to the detection of early neurotoxicity in humans

Various neurophysiological methods, including electroencephalography, electromyography, nerve conduction velocities, and evoked potential techniques, have been used to detect early signs of neurotoxicity in humans. These methods have been applied to groups of occupationally exposed workers and their referents in epidemiologic studies, to patients with suspected or proven diseases after long-term work in toxic environment, and to human subjects during or after experimental exposure. The main body of knowledge arises from epidemiologic studies of occupationally exposed subjects, and several chemicals widely used in industry have been shown to be neurotoxic. Of these, e.g., lead causing peripheral neuropathy, some solvents like carbon disulfide, n-hexane, and methyl n-butyl ketone also causing neuropathy and at times central nervous system effects as well as acryl amide have been studied using neurophysiological approaches. Several other solvents including toluene, xylene, and various mixtures of organic solvents have been suspected to be neurotoxic, and nervous system effects have been ascribed to those in several neurophysiological studies. Some studies have elucidated acute nervous system effects of ethyl alcohol or industrial solvents in experimental situations applying, for example, evoked potential techniques or electroencephalography.

Ethanol and event-related potentials: the influence of distractor stimuli

A modified auditory "oddball" task was employed to determine the effects of ethanol on event-related potentials (ERPs). Ten subjects ingested either a 0.0 or 1.0 ml/kg dosage of 94% ethanol on counterbalanced days. During each set of pre- and post-drug days, the subjects heard a frequently occurring 1000 Hz standard presented to the left ear, an infrequently occurring 2000 Hz target presented to the left ear, and an infrequently occurring 2000 Hz distractor presented to the right ear. The intensity of the distractor was varied in different conditions. Ethanol ingestion had a significant effect on a number of ERP components. The amplitudes of a vertex N1b and P2 were significantly attenuated suggesting that ethanol's influence on N1b is probably due more to a depressive effect operating at the level of sensation than on a decrease in the subject's state of attentiveness. P3 was found to be reduced in amplitude but only following the distractor and not the target, possibly reflecting an interaction of task difficulty or informational value of the stimulus. There was little evidence of a greater susceptibility of the right hemisphere compared to the left or of association areas compared to the auditory cortex.

Effects of acute ethanol administration on neocortical inhibition

The hypothesis that acutely administered ethanol could interfere with neocortical recurrent inhibition (RI) was supported. The large surface negative wave in response to antidromic stimulation of the cerebral peduncle represents a summation of inhibitory postsynaptic potentials, a measure of RI. In acute experiments on adult rats, blood alcohol levels of less than about 120 mg/100 ml slightly facilitated the surface negative wave. Higher blood alcohol levels always blocked the surface negative response. Stimulation of the somatosensory thalamic relay nuclei produced a cortical response on which ethanol had a moderate blocking effect. Conditioning-test procedures revealed that cerebral peduncle stimulation strongly blocked the thalamocortical (test) response, especially after ethanol, but thalamic stimulation (conditioning) had no effect upon the surface negative wave. This demonstrates a differential effect on the two cortical processes. Cortical RI seems to be especially sensitive to blood alcohol level, but the function of cortical RI is complex. By way of acting on RI, ethanol likely affects control of sensory input and cortical sensory organization as well as selectivity and magnitude of motor discharge.

The study of brain function impairment in fetal alcohol syndrome: some fruitful directions for research

Fetal alcohol syndrome (FAS) is the most prevalent known preventable health hazard to the human fetus by a noxious agent. It is associated with impairments of the central nervous system that are expressed in the forms of mental retardation of varying severity, learning disabilities, attentional deficits and an increased vulnerability to stress. Results of psychophysiological studies of the effects of ethanol on the central nervous system are reviewed, with the aim of exploring how conclusions derived from them can serve as testable hypotheses in FAS research. The experimental methods used in such studies are examined for their applicability to FAS research. It is concluded that FAS research effort will benefit from the inclusion of psychophysiological studies.

Effect of alcohol and task on hemispheric asymmetry of visually evoked potentials in man

The study examined the effect of a dose of alcohol producing a mean blood alcohol content of 90 mg% on components of the scalp-recorded visually evoked potential (VEP) both with and without a visual discrimination task to control the level of attention, and the interaction of amplitudinal hemispheric asymmetry of the VEP with alcohol treatment and the discrimination task. Ingestion of ethyl alcohol producing a mean blood alcohol content of 90 mg% affected VEPs recorded from the central scalp by attenuating the overall amplitude of the later VEP components (60-200 msec) and by significantly reducing hemispheric asymmetry in the amplitude of these VEP components. Alcohol attenuates VEP components P90-N120 and N120-P180, and the task of counting flashes and attending to discriminate double flashes increased amplitude of VEP components N60-P90 and P90-N120 in control and placebo conditions. Several studies have reported that the VEP recorded from the right hemisphere of human beings is larger than the VEP recorded from the homologous location in the left hemisphere. Evoked potentials recorded under control and placebo conditions in this study also demonstrated a hemispheric asymmetry with right larger than left for component P90-N120. We also found a reliable alcohol by hemispheric asymmetry interaction. Alcohol selectively depressed the amplitude of the right hemisphere VEP (P90-N120) component to a significantly greater extent than the left hemisphere VEP was affected.

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.

Effect of alcohol ingestion on regional cerebral blood flow

Regional distribution of cerebral blood flow was assessed in 10 normal social drinkers following consumption of .75 g/kg alcohol and in a control session without alcohol. Alcohol increased blood flow in the gray matter in all brain areas except the left anterior area. The results are discussed in terms of the effect of alcohol on regional cerebral activation.

Effects of ethanol on visual evoked responses in monkeys performing a memory task

The effects of ethanol on behavior and visual evoked potentials were investigated in monkeys performing a visual short-term memory task. Ethanol induced a dose-dependent deficit in performance and a prolongation of visuo-motor reaction time. The normal patterns of ocular motility were concomitantly altered. The potentials elicited in the lateral geniculate nucleus, the striate cortex, the inferotemporal cortex, the amygdala, and the mesencephalic reticular formation by a colored stimulus used by the animal in the task were attenuated by the alcohol in dose-related manner. In contrast, potentials elicited in the striate cortex and reticular formation by a brief and diffuse flash were augmented under the influence of the substance. It is inferred that ethanol can increase the reactivity of reticular and cortical structures to undifferentiated stimuli, while at the same time interfering with the basic mechanisms of visual attention and perception.

Ethanol and menstrual cycle interactions in the visual evoked response

Right and left hemisphere visual evoked responses from central locations were collected from 10 normal right-handed women in the follicular and luteal phases of their menstrual cycle. Subjects were tested sober and under 3 doses of ethanol. Amplitude and latency characteristics of the N120 and P180 components for each hemisphere were determined. Asymmetry between hemispheres for the various measurements was then calculated. The follicular phase was associated with a significant P180 latency asymmetry under baseline or placebo conditions. Virtually no asymmetry for P180 latency was present in the luteal phase. Ethanol eliminated the follicular P180 latency asymmetry and reduced the amplitude of both N120 and P180 in a dose-related fashion. The latency of the N120 component was prolonged by ethanol in a similar fashion. Interactions between menstrual cycle and ethanol occurred for both amplitude and latency of P180, but only for the response from the left hemisphere. These occurred at low or moderate doses of ethanol and illustrate the need to consider both the biphasic effects of low doses of ethanol and the possibility of lateralization of these effects to one cerebral hemisphere.

Electroencephalographic tolerance and abstinence phenomena during repeated alcohol ingestion by nonalcoholics

Certain measures of the auditory average evoked response are sensitive to alcohol and provide evidence for abstinence and tolerance during and after 10 days of alcohol consumption by nonalcoholics. Electroencephalographic techniques provide a single sensitive measure for the study of the etiology of tolerance and abstinence with particular reference to a new area of investigation with nonaddicted humans.

Effect of ethyl alcohol on visual evoked potentials

Effects of ethyl alcohol evoked potentials were studied in 12 healthy volunteers. Alcohol significantly reduced the amplitude and prolonged the latency of the N2-P2 components of the centrally derived flash evoked potential. Amplitude attenuation was positively correlated with alcohol doses of 0.8 and 1.2 g/kg. Analysis of subsets of data revealed the amplitude attenuation to be time related and not present in the initial five responses after alcohol. Possible neurochemical mechanisms related to the amplitude attenuation are discussed.

Effects of small ethanol doses on the auditory evoked transient and sustained potentials in the human EEG

Effects of small doses of ethanol on transient and sustained potentials evoked by short tones were examined. Transient and sustained potentials showed an opposite effect of ethanol. The results indicate that ethanol has different effects on neural systems underlying transient and sustained potentials evoked in the human EEG.

Combined effects of alcohol and sleep deprivation in normal young adults

The effect of combining sleep deprivation and moderate alcohol consumption in male college students differed from the effects of each treatment alone. Following either alcohol or sleep deprivation, there was mild performance impairment, decreased alertness and reduced amplitude and increased latency of cortical evoked potential (EP) components. Heart rate increased after alcohol and anxiety increased after sleep deprivation. When alcohol and sleep deprivation were combined, antagonistic effects were found for most measures (reaction time, heart rate, alertness, anxiety, latency of early EP components), but synergistic effects also occurred (performance accuracy, latency of late EP components). These effects were found in a double-blind experiment using 24 subjects. The experimental treatments were alcohol doses of 0, 0.45 and 0.90 ml/kg of 95% ethanol and 0 and 26 h of sleep deprivation.

Auditory evoked transient and sustained potentials in the human EEG: II. Effects of small doses of ethanol

The effect of small doses of ethanol (0.4 g/kg) on auditory evoked transient and sustained potentials was studied. Tones of 1-second duration were presented in trains of four stimuli (interstimulus interval = 1 second; intertrain interval = 1 minute). The electroencephalogram was recorded from derivation Cz-Al. Ethanol depressed the transient responses both at the first stimulus of the train and during repeated stimuli. The sustained potentials elicited by the first stimuli of the train were not affected by ethanol, whereas the sustained potentials elicited by repeated stimuli were larger in amplitude under the influence of ethanol than during control experiments. It is suggested that the decrease of the transient responses under the influence of ethanol is mainly due to depression of the reticular formation, whereas the increase of sustained potentials reflects ethanol-induced release of intracortical inhibition.

Auditory brain stem potentials with alcohol

Auditory brain stem potentials were recorded from unrestrained rats and from cats paralyzed with Flaxedil, before and after ingestion of intoxicating dosages of alcohol. The acute effect of alcohol was a cumulative increase in the central conduction times of successive brain stem potential peaks. Statistically significant latency changes were found for peaks attributed to neural structures as far peripherally as the medulla. This depressive influence of alcohol on sensory transmission was independent of variations in stimulus intensity and body temperature.

Acute effects of alcohol on auditory brainstem potentials in humans

Auditory brainstem potentials were recorded from human subjects before and after an intoxicating dose of alcohol. Following alcohol ingestion there were significant, progressive increases in the latencies of brainstem potential peaks III through VII. No changes in peak amplitudes were found. The results indicate that alcohol has a depressive effect on neural transmission within the primary auditory brainstem pathway.

Time course effects of marijuana and ethanol on event-related potentials

Twelve male college students received orally on different days NIMH marijuana extract calibrated to contain 0.7 mg/kg delta-9-tetrahydrocannabinol, 1.0 ml/kg 95% ethanol, and placebo in a double-blind balanced-order design. The contingent negative variation (CNV), auditory evoked potential (EP), heart rate (HR), and subjective measures of intoxication were recorded prior to drug ingestion and at regular intervals for 4.5 h postdrug. Both drugs produced significant subjective effects. Marijuana increased HR but did not have a significant effect on CNV amplitude or EP peak amplitudes and latencies. Ethanol increased HR, but not significantly, and reduced CNV amplitude and N1-P2 amplitude. Time-action curves for ethanol's effect on subjective high, HR, and N1-P2 amplitude were parallel, peaking between 0.5 and 1.5 h postdrug and returning to baseline by the end of testing. Time-action curve for ethanol's effect on the CNV showed continuing amplitude reduction throughout the test session.

Changes in fixed-ratio performance and blood alcohol levels in monkeys

Three female Bonnet monkeys prepared with indwelling venous catheters were maintained on a fixed-ratio schedule of food reinforcement until response rates were stable. The animals were then intubated with alcohol (5.0 g/kg) 30 min prior to testing. Blood alcohol concentrations (BACs) were determined every 15 min throughout the 90-min session. Each alcohol intubation was separated by 3 days and on the second control day an isocaloric sucrose solution was intubated. The results show that the alcohol-induced response suppression gradually returns to baseline levels after 5 alcohol intubations, and the BACs were concomitantly decreased. The results indicate that the reversibility of alcohol induced behavioral impairments and changes in BACs develop within similar temporal intervals.

Ethanol and marihuana effects on event-related potentials in a memory retrieval paradigm

Twelve men performed the Sternberg memory retrieval task under three experimental conditions: after oral doses of marihuana extract calibrated to contain 0.7 mg/kg delta9-tetrahydrocannabinol (THC), 1.0 ml/kg 95% ethanol, or placebo. Simultaneously, the EEG was recorded from Ca to linked ears and the EOG from leads above and below the right eye. In this task, subjects saw a set of 1 to 4 digits follwed by a warning tone that was followed 1.5 sec later by a test digit. Subjects indicated by pressing one of two buttons whether the test digit was in-set or out-of-the-set. There were no drug effects on N1 in the evoked potential to the warning tone, but P3 amplitude was smaller under THC and ethanol than under placebo. CNV amplitude in the interval between the warning tone and the test digit showed no drug effects, indicating that the subject was equally prepared for the test digit regardless of drug received. However, the latency of 50% resolution of the CNV was longer under THC than under placebo. THC also increased the reaction time for each set size by about 75 msec above the values for ethanol and placebo, the latter two not differing significantly. Set size affected N1 and P3 amplitudes and latencies and CNV amplitude, as well as 50% CNV resolution latency and reaction time, but there were no drug chi set size interactions.

Sudden toxicity of methadone in monkeys: behavioral and electrophysiological evidence

A sudden and potentially lethal toxic reaction to a previously well-tolerated maintenance dose of methadone occurred in 4 of 6 monkeys. The reaction was characterized by gross behavioral and respiratory depression and a marked attenuation of both early and late components of the visual evoked response with an increase in most latencies. The nature of the evoked response alteration suggests a widespread central nervous system depressant effect of the drug during toxicity. Concomitant with the toxic reactions were dramatic increases in plasma methadone concentrations. Therefore the observed changes in sensitivity to methadone would appear to be the consequence of a sudden shift in pharmacokinetics resulting in toxic plasma concentrations.