Acute and chronic alcohol tolerance in humans: effects of dose and consecutive days of exposure

Synaptic Mechanisms of Ethanol Tolerance and Neuroplasticity: Insights from Invertebrate Models

Alcohol tolerance is a neuroadaptive response that leads to a reduction in the effects of alcohol caused by previous exposure. Tolerance plays a critical role in the development of alcohol use disorder (AUD) because it leads to the escalation of drinking and dependence. Understanding the molecular mechanisms underlying alcohol tolerance is therefore important for the development of effective therapeutics and for understanding addiction in general. This review explores the molecular basis of alcohol tolerance in invertebrate models, Drosophila and C. elegans, focusing on synaptic transmission. Both organisms exhibit biphasic responses to ethanol and develop tolerance similar to that of mammals. Furthermore, the availability of several genetic tools makes them a great candidate to study the molecular basis of ethanol response. Studies in invertebrate models show that tolerance involves conserved changes in the neurotransmitter systems, ion channels, and synaptic proteins. These neuroadaptive changes lead to a change in neuronal excitability, most likely to compensate for the enhanced inhibition by ethanol.

Differential development of acute tolerance may explain heightened rates of impaired driving after consumption of alcohol mixed with energy drinks versus alcohol alone

Consumers of alcohol mixed with energy drinks (AmED) are more likely to drive while impaired when compared to alcohol alone consumers. In addition, acute tolerance to the internal cues of feelings of intoxication is known to contribute to maladaptive decisions to drive while impaired. Therefore, the purpose of this study was to determine whether there is differential development of acute tolerance for AmED versus alcohol alone for ratings of willingness to drive after alcohol consumption. Social drinkers (n = 12) attended 4 separate sessions where they received alcohol and energy drinks, alone and in combination. The development of acute tolerance to alcohol was assessed for several objective (a computerized cued go/no-go reaction time task) and subjective measures at matched breath alcohol concentrations (BrACs) for the ascending and descending limbs of the BrAC curve. The results indicated that alcohol administration decreased willingness to drive ratings. Acute tolerance was observed in the AmED dose condition for only the willingness to drive ratings that were significantly higher on the descending versus ascending test. Alcohol-induced impairments of the computer task performance did not exhibit any acute tolerance. Therefore, the differential development of acute tolerance may explain why many studies observe higher rates of impaired driving for AmED consumers compared to alcohol alone consumers. Because drunk driving is a major public health concern, alcohol consumers should be warned that the use of energy drink mixers with alcohol could lead to a false sense of security in one's ability to drive after drinking. (PsycINFO Database Record

Apremilast Alters Behavioral Responses to Ethanol in Mice: II. Increased Sedation, Intoxication, and Reduced Acute Functional Tolerance

BACKGROUND

In our companion paper, we reported that the phosphodiesterase type 4 inhibitor apremilast reduced ethanol (EtOH) intake and preference in different drinking models in male and female C57BL/6J mice. In this study, we measured the effects of apremilast on other behaviors that are correlated with EtOH consumption.

METHODS

The effects of apremilast (20 mg/kg) on the following behaviors were studied in male and female C57BL/6J mice: locomotor response to a novel situation; EtOH- and lithium chloride (LiCl)-induced conditioned taste aversion (CTA) to saccharin; conditioned place preference (CPP) and conditioned place avoidance (CPA) to EtOH; severity of handling-induced convulsions after EtOH administration; EtOH-induced anxiolytic-like behavior in the elevated plus maze; duration of EtOH-induced loss of righting reflex (LORR); recovery from EtOH-induced motor impairment on the rotarod; and acute functional tolerance (AFT) to EtOH's ataxic effects.

RESULTS

Apremilast did not change the acquisition of EtOH-induced CPP, severity of acute withdrawal from EtOH, or EtOH's anxiolytic-like effect. Apremilast did not alter the extinction of EtOH- or LiCl-induced CTA, but may interfere with acquisition of CTA to EtOH. Apremilast increased the acquisition of CPA to EtOH, reduced locomotor responses to a novel situation, and prolonged the duration of LORR and the recovery from acute motor incoordination induced by EtOH. The longer recovery from the ataxic effect may be attributed to reduced development of AFT to EtOH.

CONCLUSIONS

Our results suggest that apremilast increases the duration of EtOH intoxication by reducing AFT. Apremilast also reduces some aspects of general reward and increases EtOH's aversive properties, which might also contribute to its ability to reduce EtOH drinking.

A systematic review of the evidence for acute tolerance to alcohol - the "Mellanby effect"

OBJECTIVE

To review the evidence for "the Mellanby effect", that is, whether the response to a given blood alcohol concentration (BAC) is more marked when BAC is rising than at the same concentration when BAC is falling.

METHODS

We systematically searched the databases EMBASE, Medline, and Scopus up to and including December 2016 using text words "tolerance", "ascending", "descending" or "Mellanby" with Medline term "exp *alcohol/" or "exp *drinking behavior/" or equivalent. Articles were identified for further examination by title or abstract; full text articles were retained for analysis if they dealt with acute (within dose) alcohol tolerance in human subjects and provided quantitative data on both the ascending and descending parts of the BAC-time curve. Reference lists of identified works were scanned for other potentially relevant material. We extracted and analyzed data on the subjective and objective assessment of alcohol effects.

RESULTS

We identified and screened 386 unique articles, of which 127 full-text articles were assessed; one provided no qualitative results, 62 involved no human study, 25 did not consider acute tolerance within dose, and 13 failed to provide data on both ascending and descending BAC. We extracted data from the 26 remaining articles. The studies were highly heterogeneous. Most were small, examining a total of 770 subjects, of whom 564 received alcohol and were analyzed in groups of median size 10 (range 5-38), sometimes subdivided on the basis of drinking or family history. Subjects were often young white men. Doses of alcohol and rates of administration differed. Performance was assessed by at least 26 different methods, some of which measured many variables. We examined only results of studies which compared results for a given alcohol concentration (C) measured on the ascending limb (C_up) and the descending limb (C_down) of the BAC-time curve, whether in paired or parallel-group studies. When subjects were given alcohol in more than one session, we considered results from the first session only. Rating at C_down was better than at C_up for some measures, as expected if the Mellanby effect were operating. For example, subjects rated themselves less intoxicated on the descending limb than at the same concentration on the ascending limb in 12/13 trials including 229 subjects that gave statistically significant results. In 9 trials with a total of 139 subjects, mean difference could be calculated; weighted for study size, it was 29% [range 24-74%]. Willingness to drive was significantly greater in 4 of 6 studies including a total of 105 subjects; weighted mean difference increased by 207% [range 79-300%]. By contrast, measure of driving ability in three groups of a total of 200 trials in 57 subjects showed worse performance by a weighted mean of 96% [range 3-566%]. In three trials that tested inhibitory control (cued go or no-go response times), weighted mean performance was 30% [range 14-65%] worse on the descending limb.

CONCLUSIONS

The "Mellanby effect" has been demonstrated for subjective intoxication and willingness to drive, both of which are more affected at a stated ethanol concentration when BAC is rising than at the same concentration when BAC is falling. By contrast, objective measures of skills necessary for safe driving, such as response to inhibitory cues and skills measured on driving simulators, were generally worse on the descending part of the BAC-time curve for the same BAC.

Impact of day-of-injury alcohol consumption on outcomes after traumatic brain injury: A meta-analysis

Although a known risk factor for traumatic brain injury (TBI), alcohol has been found to both promote and protect against secondary brain damage. However, it is presently unclear whether the cognitive, psychological and medical/functional outcomes of adults who have consumed alcohol prior to sustaining a TBI differ from those who have not. This meta-analysis examined the outcomes of groups that differed in terms of their day-of-injury (DOI) blood alcohol levels (BALs) by comparing positive with zero BAL (BAL⁺/BAL^-) and high with low BAL (BAL^high/BAL^low) samples. The PubMed, PsycINFO, EMBASE, and Scopus databases were searched from inception until the end of March 2015. Hedge's g effects (continuous data) and odds ratios (categorical data) were calculated for 27 studies that compared either the outcomes of BAL⁺ and BAL^- groups or BAL^high and BAL^low groups. BAL⁺ was associated with significantly poorer cognitive outcomes (overall and on general tests) and higher levels of disability, and BAL^high was associated with shorter stays in intensive care. More generally, however, most effect sizes were small to low-moderate in size, non-significant and inconsistent in their direction. Although DOI alcohol consumption increases the risk of sustaining a TBI, it is not consistently associated with better or worse outcomes, other than subtle cognitive deficits; the source of which remains to be determined.

Recent advances with a novel model organism: alcohol tolerance and sensitization in zebrafish (Danio rerio)

Alcohol abuse and dependence are a rapidly growing problem with few treatment options available. The zebrafish has become a popular animal model for behavioral neuroscience. This species may be appropriate for investigating the effects of alcohol on the vertebrate brain. In the current review, we examine the literature by discussing how alcohol alters behavior in zebrafish and how it may affect biological correlates. We focus on two phenomena that are often examined in the context of alcohol-induced neuroplasticity. Alcohol tolerance (a progressive decrease in the effect of alcohol over time) is often observed following continuous (chronic) exposure to low concentrations of alcohol. Alcohol sensitization also called reverse tolerance (a progressive increase in the effect of alcohol over time) is often observed following repeated discrete exposures to higher concentrations of alcohol. These two phenomena may underlie the development and maintenance of alcohol addiction. The phenotypical characterization of these responses in zebrafish may be the first important steps in establishing this species as a tool for the analysis of the molecular and neurobiological mechanisms underlying human alcohol addiction.

Genetic studies of acute tolerance, rapid tolerance, and drinking in the dark in the LXS recombinant inbred strains

BACKGROUND

We hypothesized that rapid tolerance (1-day tolerance) for the duration of the loss of righting reflex ("sleep time" [ST]) was mediated by an increase in acute functional tolerance (AFT). We also hypothesized that increased AFT would correspond to increased drinking. These questions were addressed using the LXS recombinant inbred mouse strain panel.

METHODS

Mice were given a pretreatment dose of either saline or 5 g/kg alcohol on day 1. On day 2, mice were tested for ST (4.1 g/kg) using a method with which it is possible to accurately assess AFT. Genetic correlation analysis was conducted among the ST-related variables and also with "drinking in the dark" (DID) which was previously measured by Saba and colleagues (2011).

RESULTS

Saline-pretreated mice showed a continuous distribution of ST ranging from ~40 minutes to over 3 hours. Of the 43 strains tested, 9 showed significantly decreased ST after alcohol pretreatment, while in 3 strains, ST was significantly increased. AFT scores ranged from 0 to over 200 mg% in the saline group, and in the alcohol group, 8 strains showed a significant increase in AFT and 2 strains showed significant decrease in AFT. In the saline group, AFT was significantly correlated with ST (r = -0.47), but not in the alcohol group (r = -0.22). DID was significantly correlated with only AFT in the alcohol pretreated group (r = 0.64).

CONCLUSIONS

The results suggest that AFT is an important component of the overall ST response, but that the alcohol pretreatment-induced change in AFT does not contribute to rapid ST tolerance. The significant correlation between DID and AFT in the alcohol group suggests that AFT may be a more relevant predictor of drinking behavior than the static measurement of ST. Moreover, preexposure to alcohol seems to change AFT in a way that makes it an even stronger predictor of drinking behavior.

A comparison of the central nervous system effects of alcohol at pseudo-steady state in Caucasian and expatriate Japanese healthy male volunteers

In general, Japanese and Caucasians differ in their response to alcohol. To investigate these differences the alcohol clamping method can be used. This strictly controlled infusion regimen provides a reliable tool to study contrasts in central nervous system (CNS) effects and/or alcohol disposition. In this study, twelve Japanese and twelve Caucasian healthy volunteers received two concentrations of intravenous alcohol or placebo using the alcohol clamp. Infusion rates during the steady state phase were used to compare alcohol clearance between the subgroups. Central nervous system (CNS) effects were frequently measured throughout the clamp. On average, significantly lower amounts of alcohol were needed to maintain similar stable concentrations in the Japanese group. However, these differences disappeared when values were corrected for lean body mass. The most pronounced pharmacodynamic differences between the groups were observed on body sway and on the visual analogue scale for subjective alcohol effects, mainly at the highest dose level. The alcohol clamp seems a useful method to compare differences in alcohol metabolism between groups. Some CNS effects of alcohol differed clearly between Japanese and Caucasians, but others did not, even though alcohol levels were stable and similar between the two groups.

Differential effects of moderate alcohol consumption on performance among older and younger adults

BACKGROUND

Studies exploring differential effects of acute alcohol consumption on younger and older adults are lacking within the field of alcohol research, especially those using moderate doses. Previous studies addressing this question have tended to use complex behavioral tasks too broad to isolate specific neurocognitive processes affected by both alcohol and aging. Compromises in cognitive efficiency (i.e., the ability to respond both quickly and accurately) have previously been identified in both elderly and acutely intoxicated individuals.

METHODS

The present study employed a visual-spatial, 2-choice reaction time (RT) task to evaluate the interactive effects of aging and alcohol on cognitive efficiency. Our primary outcome measure was an efficiency ratio derived from each participant's response accuracy (ACC) and mean RT (%correct/RT). Younger (25 to 35; n = 22) and older (55 to 74; n = 37) participants were randomly assigned to receive either a placebo or moderate alcohol dose intended to produce a peak breath alcohol concentration of 0.04%. Participants performed the task at peak alcohol levels.

RESULTS

A significant interaction between age group and dose assignment was observed, F(3, 55) = 4.86, p = 0.03, for the efficiency ratio. Younger participants who received alcohol performed significantly better than did their older counterparts regardless of alcohol condition and despite no differences in performance between the 2 age groups in the placebo condition. Additional correlation analyses between ACC and RT suggested that moderately intoxicated older adults become more accurate as response times increase. This relationship was not observed in older adults in the placebo condition.

CONCLUSIONS

These data suggest that healthy individuals exhibit a differential susceptibility to the effects of alcohol depending on their age. Unfortunately, because of the presumed safety of moderate alcohol doses and a lack of studies investigating the interactive effects of acute alcohol consumption and aging, most individuals are unlikely to be aware of this relationship between alcohol consumption and age.

Alcohol and cognition in the elderly: a review

Consumption of large amounts of alcohol is known to have negative effects, but consumption in smaller amounts may be protective. The effect of alcohol may be greater in the elderly than in younger adults, particularly with regard to cognition. However, the drinking pattern that will provide optimal protection against dementia and cognitive decline in the elderly has not been systematically investigated. The present paper is a critical review of research on the effect of alcohol on cognitive function and dementia in the elderly. Studies published from 1971 to 2011 related to alcohol and cognition in the elderly were reviewed using a PubMed search. Alcohol may have both a neurotoxic and neuroprotective effect. Longitudinal and brain imaging studies in the elderly show that excessive alcohol consumption may increase the risk of cognitive dysfunction and dementia, but low to moderate alcohol intake may protect against cognitive decline and dementia and provide cardiovascular benefits. Evidence suggesting that low to moderate alcohol consumption in the elderly protects against cognitive decline and dementia exists; however, because of varying methodology and a lack of standardized definitions, these findings should be interpreted with caution. It is important to conduct more, well-designed studies to identify the alcohol drinking pattern that will optimally protect the elderly against cognitive decline and dementia.

Attenuation of microglial and IL-1 signaling protects mice from acute alcohol-induced sedation and/or motor impairment

Alcohol-induced proinflammatory central immune signaling has been implicated in the chronic neurotoxic actions of alcohol, although little work has examined if these non-neuronal actions contribute to the acute behavioral responses elicited by alcohol administration. The present study examined if acute alcohol-induced sedation (loss of righting reflex, sleep time test) and motor impairment (rotarod test) were influenced by acute alcohol-induced microglial-dependent central immune signaling. Inhibition of acute alcohol-induced central immune signaling, through the reduction of proinflammatory microglial activation with minocycline, or by blocking interleukin-1 (IL-1) receptor signaling using IL-1 receptor antagonist (IL-1ra), reduced acute alcohol-induced sedation in mice. Mice treated with IL-1ra recovered faster from acute alcohol-induced motor impairment than control animals. However, minocycline led to greater motor impairment induced by alcohol, implicating different mechanisms in alcohol-induced sedation and motor impairment. At a cellular level, IκBα protein levels in mixed hippocampal cells responded rapidly to alcohol in a time-dependent manner, and both minocycline and IL-1ra attenuated the elevated levels of IκBα protein by alcohol. Collectively these data suggest that alcohol is capable of rapid modification of proinflammatory immune signaling in the brain and this contributes significantly to the pharmacology of alcohol.

Age differences in the expression of acute and chronic tolerance to ethanol in male and female rats

BACKGROUND

Ontogenetic differences in response to ethanol (EtOH) challenge have been observed under a variety of circumstances, including varying reports of developmental differences in the expression of tolerance to EtOH. The purpose of the present experiment was to further explore potential differences in acute (AT) and chronic (CT) tolerance expression between adolescent and adult, male and female Sprague-Dawley rats, using the social interaction test.

METHODS

AT and CT to the social suppressing effects of a moderate dose of EtOH was assessed in adolescent and adult rats following intraperitoneal injections of 2.0 g/kg EtOH or saline daily for 10 days. At test, adults and adolescents were challenged with 1.0 or 1.25 g/kg EtOH, respectively, with AT and CT assessed at 5 and 25 minutes postinjection using ratios of impairment to brain ethanol concentrations (BrECs) at each time period (CT) and within-session declines in impairment relative to BrECs (AT).

RESULTS

In adolescents, 10 days of EtOH pre-exposure resulted in evidence of CT at 25 minutes postinjection, perhaps associated with an enhanced expression of AT. Among adults, signs of CT were seen at 5 minutes postinjection in adults, and may reflect neuroadaptations unassociated with AT, as with evidence of tolerance emerging only in adult control animals repeatedly exposed to saline injection prior to EtOH challenge on test day. Sex differences in tolerance expression were not observed at either age.

CONCLUSIONS

Our results show ontogenetic differences between adolescents and adults in the short- and long-term neuroadaptations that they express in response to repeated perturbations with EtOH. Together these findings add age of exposure and time of testing within the intoxication period as critical variables to be considered when exploring the complex relationship between AT and CT.

Alcohol levels do not accurately predict physical or mental impairment in ethanol-tolerant subjects: relevance to emergency medicine and dram shop laws

The human body and the central nervous system can develop tremendous tolerance to ethanol. Mental and physical dysfunctions from ethanol, in an alcohol-tolerant individual, do not consistently correlate with ethanol levels traditionally used to define intoxication, or even lethality, in a nontolerant subject. Attempting to relate observed signs of alcohol intoxication or impairment, or to evaluate sobriety, by quantifying blood alcohol levels can be misleading, if not impossible. We report a case demonstrating the disconnect between alcohol levels and generally assigned parameters of intoxication and impairment. In this case, an alcohol-tolerant man, with a serum ethanol level of 515 mg/dl, appeared neurologically intact and cognitively normal. This individual was without objective signs of impairment or intoxication by repeated evaluations by experienced emergency physicians. In alcohol-tolerant individuals, blood alcohol levels cannot always be predicted by and do not necessarily correlate with outward appearance, overt signs of intoxication, or physical examination. This phenomenon must be acknowledged when analyzing medical decision making in the emergency department or when evaluating the ability of bartenders and party hosts to identify intoxication in dram shop cases.

Ethanol effects on GABA-gated current in a model of increased alpha4betadelta GABAA receptor expression depend on time course and preexposure to low concentrations of the drug

Several recent studies have suggested that alphabetadelta subtypes of gamma-aminobutyric acid type A (GABAA) receptors (delta-GABAR) are a target for low dose ethanol (<30 mM). However, there are also conflicting reports suggesting that only high doses of the drug (100 mM) modulate these receptors. In addition, the studies which have demonstrated a clear effect of low dose ethanol on delta-GABAR find different effective concentrations for this effect. Here, we test the hypothesis that the apparent disparity in effective concentration is due to time-course effects when low (1-3 mM) dose ethanol is preapplied. To this end, we tested ethanol effects on native GABAR in CA1 hippocampus in a model of increased alpha4betadelta GABAR expression following 48h administration of the GABA-modulatory steroid THP (3alpha-OH-5beta-pregnan-20-one) to adult, female rats. GABA(EC20)-gated current was recorded with whole-cell patch clamp procedures from acutely isolated pyramidal cells. We assessed ethanol's effect on GABA-gated current using either (1) 2-5 min application of ethanol in increasing concentrations (0.1-30 mM) or (2) coadministration of ethanol with GABA. Two minute application of 1-3 mM ethanol produced optimal potentiation of GABA-gated current following steroid treatment, with higher concentrations less effective. In contrast, 30 mM ethanol produced optimal effects when ethanol was not preapplied. However, following preapplication of 1mM ethanol, 30 mM ethanol decreased the peak GABA-gated current. These findings suggest that ethanol may act at multiple interacting sites to affect GABAR efficacy and desensitization. These data also suggest that ethanol effects on GABA-gated current are affected by the time course of exposure and previous exposure to low concentrations of the drug.

Ontogeny of acute tolerance to ethanol-induced social inhibition in Sprague-Dawley rats

BACKGROUND

Adolescent rats are less sensitive than adults to a number of acute effects of ethanol, including ethanol-induced social inhibition. Adolescent insensitivity to the suppressing effects of ethanol on social interactions could be related in part to age differences in compensatory responses, including acute tolerance, that serve to counteract these inhibitory effects of ethanol. The present study explored ontogenetic development of acute tolerance within 30 minutes after administration of a relatively low ethanol dose, using ethanol-induced social impairment as the target response measure.

METHODS

Overall social activity was examined following challenge with 1 g/kg ethanol (intraperitoneally) at 2 postinjection intervals (5 or 30 minutes) in early [postnatal day (P) 28], mid (P35), or late (P42) adolescent or adult (P70) group-housed male and female Sprague-Dawley rats (Experiment 1). Blood and brain ethanol concentrations (BECs and BrECs) were assessed in separate groups of animals 5 or 30 minutes after ethanol administration (Experiment 2). Expression of acute tolerance was examined by assessing the relationship between BrECs and the degree of social impairment in individual animals at P28, P35, P42, and P70 during early recovery period (up to 30 minutes) following acute ethanol challenge (Experiment 3).

RESULTS

Effects of ethanol on overall social activity were age-dependent and time-dependent. Whereas all age groups showed equivalent ethanol-induced social inhibition 5 minutes after injection, testing at 30 minutes revealed marked age differences. Social inhibition was still pronounced at this time in adults, but was diminished in an age-related manner at younger ages (Experiment 1). In contrast to the ontogenetic differences in rates of decline in social impairment across time, decreases in brain and blood ethanol levels over time were similar across age (Experiment 2). Only P28 and P35 adolescents showed acute tolerance to ethanol-induced social inhibition, as indexed by an increasing time-dependent dissociation between BrECs and ethanol-induced social impairment, with social impairment declining faster than BrECs (Experiment 3).

CONCLUSIONS

This is the first study to document enhanced acute tolerance in adolescent rats relative to adult animals at nonhypnotic doses of ethanol. The greater expression of acute tolerance in young animals may reflect an enhanced predisposition of their nervous systems to respond rapidly to even modest doses of ethanol with compensatory adaptations. A greater propensity of early adolescents to develop acute tolerance may contribute to their resistance to adverse effects of ethanol, thereby permitting heavy drinking at this age and placing early adolescents at higher risk for extensive alcohol use.

Memory encoding and retrieval on the ascending and descending limbs of the blood alcohol concentration curve

RATIONALE

Little is known about acute effects of alcohol on memory encoding and retrieval on different limbs (ascending and descending) of the blood alcohol concentration (BAC) curve.

OBJECTIVES

This extensive experiment was designed to examine alcohol's effects on memory encoding and retrieval throughout a protracted drinking episode.

METHODS

In a 9-h session, male participants consumed either alcohol (1 ml/kg) or placebo (n = 32/32) over a period of 90 min and learned various materials in different memory tasks before, during, and after consuming the drinks, while their BAC levels were monitored. A week later, in a similar session, they were tested on learned materials before, during, and after drinking. Mood was assessed throughout both sessions.

RESULTS

Alcohol impaired recall of words more than recognition, and cued recall most severely. Perceptual priming and picture recognition were not affected by alcohol. Alcohol impaired encoding in cued recall, recognition of completed word fragments, and free recall regardless of limb, but impaired retrieval in word recognition only during the ascending BAC. Alcohol increased negative mood on the descending limb during the first session, and on the ascending limb during the second session.

CONCLUSIONS

Under naturalistic drinking conditions, alcohol's effects on memory depend on task, memory process, and limb of the BAC curve. The differential effects of alcohol on retrieval during the ascending and descending limbs demonstrate the importance of examining the differential effects on the two limbs.

Deficits of respiratory-cardiac coupling in heavy drinkers

1. Physiological evidence of chronic alcohol abuse prior to the onset of clinical signs of alcohol dependence is difficult to obtain The purpose of this study was to search for possible non-invasive indicators for chronic alcohol consumption yielding information in addition to conventional biological markers. 2. The authors investigated the relationship between respiratory-cardiac coupling and blood alcohol concentration (BAC) in male subjects who lost their driver's license from drunk driving. 3. We found that subjects who had a high BAC level (0.16-0.31% at the time of offense) show altered respiratory sinus arrhythmia (RSA) and, in particular, an altered heart-rate response to auditory stimulation and compared them to a control group of social drinkers. Normal subjects showed a pronounced acoustic heart-rate response, i.e., particularly during expiration there was a difference between the interbeat-interval (IBI) traces with and without auditory stimulation. Subjects who had lost their driver's license from drunk driving had an overall severely reduced heart-rate response, that was even absent particularly in the subgroup having high BAC values (0.21-0.31%). The authors also found some evidence that in the latter subgroup IBI, RSA, and acoustic heart-rate responses partially recover after a six-month period of abstinence. 4. Specific parameters of the acoustic heart-rate response are changed in our group of alcohol abusers presumably, due to impairment of vagal function. These parameters may therefore be useful to serve as a non-invasive measure of alcohol abuse.

Acute tolerance during intravenous infusion of alcohol: comparison of performance during ascending and steady state concentrations--a pilot study

Although acute tolerance (AT) to alcohol has been demonstrated in many single-dose studies, the existence of AT at steady state concentrations of alcohol has been questioned. In the present study, six subjects were examined as (1) 7.5% alcohol or (2) placebo was administered intravenously (IV). The order of the infusions was randomized. The alcohol infusions were designed to result in similar blood alcohol concentrations at 20, 60, and 140 min (approximately 0. 7 per thousand). At 20 min, the concentrations were rising; the steady state (+/-0.10 per thousand) was reached after 60 min and continued until 140 min. Three reaction time (RT) tests from the automated psychological test system were used (simple RT, two-choice RT, and two-choice RT with auditory inhibition). When the performance of the subjects was compared at rising and steady-state concentrations of alcohol, AT was shown for the most complex task requiring parallel processing, i.e., RT with failed inhibition, test. However, at steady state (i.e., 60 vs. 140 min), AT was not found for any of the tests. Further, the analysis showed that the test results of different individuals were related to their estimated normal alcohol consumption and that these differences presumably influenced the test results in accordance with our earlier findings.

Acute alcohol tolerance in social drinkers: changes in subjective effects dependent on the alcohol dose and prior alcohol experience

Using subjective ratings of the degree of alcohol intoxication, the interaction between the drinking history of the subjects, the alcohol dose, and acute alcohol tolerance were examined in light and moderate alcohol consumers (N = 10). Both groups of subjects were tested with doses of alcohol corresponding to 0.5 and 1.0 g/kg. Dose order was random and tests were carried out with an interval of 1 week. Reports of the subjects' previous experience with these doses of alcohol indicated that the moderate consumers ingested the lower (but not the higher) of the doses quite regularly, whereas light consumers were rather inexperienced with both of the doses. Comparison of blood alcohol concentrations as measured by breath and blood analysis yielded slightly different results, the concentrations being significantly higher as measured by breath analysis. This result was mainly associated with the initial phases, where this difference was greatest. Acute tolerance was assessed by comparing the ratings at equal concentrations of alcohol on the ascending and the descending limbs of the alcohol concentration curve. Due to the lag in the measurements of breath and blood alcohol concentrations, the outcome of the evaluations of acute tolerance was also influenced by whether breath or blood alcohol concentrations were used to obtain similar concentrations in both phases. Results based on the breath alcohol concentrations showed that in light alcohol consumers, acute tolerance was demonstrated for both of the doses. In moderate alcohol consumers only the higher of the doses produced evidence for acute tolerance. However, if comparisons are based on blood alcohol concentrations, moderate alcohol consumers also show an apparent acute tolerance for the lower of the doses tested. The present results clearly demonstrate the complexity of the acute tolerance phenomenon, and emphasize the fact that the results are dependent on the dose of alcohol, the subjects' prior experience with alcohol as well as the procedure used for measuring alcohol concentration.

Acute alcohol tolerance in cognitive and psychomotor performance: influence of the alcohol dose and prior alcohol experience

Using tests for cognitive performance (the Pauli test) and psychomotor coordination (the Pursuit Rotor test), the interaction between the drinking history of the subjects, the alcohol dose, and acute alcohol tolerance were examined in light and moderate alcohol consumers (N = 10). Both groups of subjects were tested with doses of alcohol corresponding to 0.5 and 1.0 g/kg. Dose order was random and tests were carried out at an interval of 1 week. Reports of the subjects' previous experience with alcohol indicated that the moderate consumers ingested alcohol in higher quantities than the light consumers. The light consumers were rather inexperienced with frequent alcohol consumption at the quantities investigated, as were the moderate consumers for the higher of the alcohol doses used. Acute tolerance was assessed by comparing performance at equal concentrations of alcohol on the ascending and the descending limbs of the alcohol concentration curve. In the test for cognitive performance, both doses of alcohol in light alcohol consumers yielded significant differences between the ascending and descending limbs of the alcohol concentration curve, suggesting the existence of acute tolerance. In the moderate alcohol consumers, only a tendency to acute tolerance was observed for the higher of the doses tested. In the test for the psychomotor performance, both of the measures of frequency (of misses) and duration (of time outside the target area) were used. The results showed that in the light consumers, acute tolerance was seen for both of the doses, and to some extent for both of the dependent measures (frequency and duration) investigated. However, in the moderate alcohol consumers, acute tolerance was only observed for the higher of the doses and only for the duration measure. Given the difference in drinking history between the two groups of subjects, the implication would be that when the dose of alcohol exceeds the subjects' prior experience, acute tolerance seems inevitable. The present results clearly demonstrate the complexity of the acute tolerance phenomenon, and emphasize the fact that the results are dependent on the subjects' prior experience with alcohol as well as the dose of alcohol ingested, and consequently suggest the interaction between acute and chronic alcohol tolerance.

A PC-based software test for measuring alcohol and drug effects in human subjects

A new software-based visual search and divided-attention test of cognitive performance was developed and evaluated in an alcohol dose-response study with 24 human subjects aged 21-62 years. The test used language-free, color, graphic displays to represent the visuospatial demands of driving. Cognitive demands were increased over previous hardware-based tests, and the motor skills required for the test involved minimal eye movements and eye-hand coordination. Repeated performance on the test was evaluated with a latin-square design by using a placebo and two alcohol doses, low (0.48 g/kg/LBM) and moderate (0.72 g/kg/LBM). The data on 7 females and 17 males yielded significant falling and rising impairment effects coincident with moderate rising and falling breath alcohol levels (mean peak BrALs = 0.045 g/dl and 0.079 g/dl). None of the subjects reported eye-strain or psychomotor fatigue as compared with previous tests. The high sensitivity/variance relative to use in basic and applied research, and worksite fitness-for-duty testing, was discussed. The most distinct advantage of a software-based test that operates on readily available PCs is that it can be widely distributed to researchers with a common reference to compare a variety of alcohol and drug effects.

Alcohol pharmacodynamics in young-elderly adults contrasted with young and middle-aged subjects

Effects of aging on ethyl alcohol (EtOH) pharmacodynamics were examined over progressive dosing schedules (0.4, 0.6, 0.8, 1.0 g/kg) in groups of young (25.0 +/- 2.9 years), middle-aged (41.1 +/- 6.6 years), and young-elderly adults (60.9 +/- 2.6 years) using three computerized cognitive-neuromotor tasks: digit-symbol substitution (DSS), keypad reaction time (KRT), and subcritical tracking (SCT). Hysteresis curves of performance impairment (adjusted for pre-drug baseline) as a function of blood alcohol concentration (BAC) were examined for time-course effects, and regression analyses were performed to assess the contribution of age beyond that accounted for by BAC. Results reflected differences in the patterning but not magnitude of impairment for elderly subjects, with earlier decrements and more rapid acute tolerance observed for DSS, in conjunction with less pharmacodynamic sensitivity for SCT. Regression analyses furthermore indicated that age and impairment were negatively related, arguing against synergistic intoxication effects as a function of aging. Analyses specifically comparing performance at baseline versus legally intoxicating BACs (> 1.0 mg/ml) likewise reflected a lack of interactive effects involving the elderly. Elderly subjects nevertheless exhibited significantly lower baseline performance for DSS and KRT than young subjects and achieved higher BACs with equivalent doses. These latter findings support the exercise of caution by elderly individuals consuming EtOH prior to engaging in neuromotor pursuits such as driving.

Acute tolerance to ethanol inhibition of NMDA-mediated EPSPs in the CA1 region of the rat hippocampus

The time course of ethanol-induced inhibition of NMDA-mediated synaptic activity was studied in brain slices using extracellular electrophysiological techniques in the CA1 region of the hippocampus. Bath application of 60 mM ethanol inhibited NMDA-mediated field excitatory postsynaptic potentials (EPSPs) by at least 45% in 7/11 of the slices tested, with the remaining 4 slices inhibited by 8.7-35%. Most slices inhibited by at least 45% showed a significant reduction in ethanol inhibition over a 15 min ethanol exposure period, suggesting the development of acute tolerance. In a second set of experiments, tolerance to ethanol-induced inhibition of NMDA-mediated EPSPs that developed over time during the first ethanol exposure persisted during a second ethanol exposure. In contrast to ethanol, inhibition of EPSPs by the NMDA antagonist DL-2-amino-5-phosphonopentanoic acid (APV) remained stable during a comparable application of the drug. These results suggest that acute tolerance can develop to ethanol inhibition of NMDA mediated synaptic activity in the hippocampus.