EEG spectral phenotypes: heritability and association with marijuana and alcohol dependence in an American Indian community study

Native Americans have some of the highest rates of marijuana and alcohol use and abuse, yet neurobiological measures associated with dependence on these substances in this population remain unknown. The present investigation evaluated the heritability of spectral characteristics of the electroencephalogram (EEG) and their correlation with marijuana and alcohol dependence in an American Indian community. Participants (n=626) were evaluated for marijuana (MJ) and alcohol (ALC) dependence, as well as other psychiatric disorders. EEGs were collected from six cortical sites and spectral power determined in five frequency bands (delta 1.0-4.0 Hz, theta 4.0-7.5 Hz, alpha 7.5-12.0 Hz, low beta 12.0-20.0 Hz and high beta/gamma 20-50 Hz). The estimated heritability (h(2)) of the EEG phenotypes was calculated using SOLAR, and ranged from 0.16 to 0.67. Stepwise linear regression was used to detect correlations between MJ and ALC dependence and the spectral characteristics of the EEG using a model that took into account: age, gender, Native American Heritage (NAH) and a lifetime diagnosis of antisocial personality and/or conduct disorder (ASPD/CD). Increases in spectral power in the delta frequency range, were significantly correlated with gender (p<0.001) and marijuana dependence (p<0.003). Gender, age, NAH and ASPD/CD were all significantly (p<0.001) correlated with theta, alpha and beta band power, whereas alcohol dependence (p<0.01), gender (p<0.001), and ASPD/CD (p<0.001) were all correlated with high beta/gamma band power. These data suggest that the traits of EEG delta and high beta/gamma activity are correlated with MJ dependence and alcohol dependence, respectively, in this community sample of Native Americans.

Identification of a novel cytosolic aldehyde dehydrogenase allele, ALDH1A1*4

This paper reports the identification of a novel cytosolic aldehyde dehydrogenase 1 (ALDHIAI) allele. One hundred and sixty-two Indo-Trinidadian and 85 Afro-Trinidadian individuals were genotyped. A novel ALDHIAI allele, ALDHIAI*4, was identified in an Indo-Trinidadian alcoholic with an A inserted at position -554 relative to the translational start site, +1. It was concluded that a wider cross-section of individuals needs to be evaluated in order to determine the representative frequency of the allele, and to see if it is associated with risk of alcoholism.

Milk consumption during adolescence decreases alcohol drinking in adulthood

Early onset of alcohol consumption increases the risk for the development of dependence. Whether adolescent consumption of other highly palatable solutions may also affect alcohol drinking in adulthood is not known. The purpose of this study was to determine the effects of adolescent consumption of four solutions: water, sucrose, sucrose-milk and milk on ethanol drinking in adult rats. Rats had limited access to one of the four solutions from day PND 29 to PND 51 and were subsequently trained to consume ethanol (E) using a sucrose (S) fade-out procedure. Adolescent consumption of sucrose and sucrose-milk solutions increased intake of 2.5% E when it was combined with 10% S but it had no effect on the drinking of 10% E alone. Adolescent consumption of milk and sucrose-milk significantly decreased the intake of 10% E when it was combined with 10% S, and milk significantly reduced 10% E consumption alone and when it was combined with 5% S. Adolescent exposure to the sucrose-milk and sucrose solutions was also found to increase sucrose and sucrose-milk consumption. Our findings suggest adolescent exposure to sucrose increases, whereas, exposure to milk reduces ethanol consumption in adult rats. Our results may provide a new theoretical approach to the early prevention of alcoholism.

Appetitive motivational experience during adolescence results in enhanced alcohol consumption during adulthood

Exposure to alcohol during adolescence is predictive of adult alcohol abuse and dependence. The present experiment was designed to measure the impact of appetitive motivational engagement with ethanol during adolescence on adult ethanol consumption. To this end, a group of adolescent male Wistar rats was allowed to traverse an operant runway to obtain access to a sweetened 10% ethanol solution (wt/vol) over 18 sessions. An additional yoked-control group was allowed access to an identical solution; however, exposure to the solution was contingent on the experimental groups entry into the goal box of the runway. Once the adolescent exposure sessions were completed, the animals were allowed to mature into adults and then tested for differences in ethanol consumption during 30-min 2-bottle limited access sessions. Following 14 ethanol consumption sessions during adulthood, a naltrexone dose-response challenge (0-0.4 mg/kg) was initiated for both groups. The results of the experiment showed that the animals allowed to traverse the runway during adolescence displayed increased ethanol consumption during adulthood when compared to the yoked-control group. In addition, both groups showed dose-dependent attenuation of ethanol consumption by naltrexone. Thus, appetitive motivational experience during adolescence can impact adult ethanol consummatory behavior, a process that appears to involve common reinforcement-related neural substrates. This model should prove useful in delineating appetitive motivation-related factors that contribute to excessive ethanol consumption.

Tumor necrosis factor antagonism normalizes rapid eye movement sleep in alcohol dependence

BACKGROUND

In alcohol dependence, markers of inflammation are associated with increases in rapid eye movement (REM) sleep, which is thought to be a prognostic indicator of alcohol relapse. This study was undertaken to test whether blockade of biologically active tumor necrosis factor-alpha (TNF-alpha) normalizes REM sleep in alcohol-dependent adults.

METHODS

In a randomized, placebo-controlled, double-blind, crossover trial, 18 abstinent alcohol-dependent male adults received a single dose of etanercept (25 mg) versus placebo in a counterbalanced order. Polysomnographic sleep was measured at baseline and for 3 nights after the acute dose of etanercept or placebo.

RESULTS

Compared with placebo, administration of etanercept produced significant decreases in the amount and percentage of REM sleep. Decreases in REM sleep were robust and approached low levels typically found in age-comparable control subjects. Individual differences in biologically active drug as indexed by circulating levels of soluble tumor necrosis factor receptor II negatively correlated with the percentage of REM sleep.

CONCLUSIONS

Pharmacologic neutralization of TNF-alpha activity is associated with significant reductions in REM sleep in abstinent alcohol-dependent patients. These data suggest that circulating levels of TNF-alpha may have a physiologic role in the regulation of REM sleep in humans.

Heritability and a genome-wide linkage analysis of a Type II/B cluster construct for cannabis dependence in an American Indian community

Subtyping of substance dependence disorders holds promise for a number of important research areas including phenotyping for genetic studies, characterizing clinical course, and matching treatment and prevention strategies. This study sought to investigate whether a dichotomous construct similar to Babor's Types A/B and Cloninger's Types I/II for alcohol dependence can be identified for cannabis dependence in a Native American sample. In addition, heritability of this construct and its behavior in a genetic linkage analyses were evaluated. Information on cannabis use and dependence symptoms and other psychiatric disorders was obtained using the Semi-Structured Assessment for the Genetics of Alcoholism from a community sample of 606 American Indians. Hierarchical average linkage and K means cluster analysis was used, and a three-cluster solution was found to generate the best separation of variables. Ninety-one per cent of cannabis-dependent participants fell into one of the two subtypes: Type A/I cluster (n = 114, 56%) and Type B/II cluster (n = 70, 35%). Heritability (estimated using Sequential Oligogenic Linkage Analysis Routines) was only significant for the Type B/II cluster (h(2) = 0.44, SE = 0.18, P < 0.01). Evidence for linkage was found for the Type B/II cluster (versus no diagnosis) on chromosome 16 [at 139 centimorgans (cM), Log of the Odds (LOD) score = 4.4], and on chromosome 19 (at 74 cM, LOD score = 6.4). Regions of interest for this phenotype (LOD > 1.5) were also located on chromosomes 14, 21, 22. These findings suggest that a Type B/II cannabis dependence phenotype can be identified in this population and that it is in part heritable and linked to areas of the genome identified previously for drug dependence phenotypes in this population as well as in other studies.

Event-related oscillations as risk markers in genetic mouse models of high alcohol preference

Mouse models have been developed to simulate several relevant human traits associated with alcohol use and dependence. However, the neurophysiological substrates regulating these traits remain to be completely elucidated. We have previously demonstrated that differences in the event-related potential (ERP) responses can be found that distinguish high-alcohol preferring from low alcohol preferring mice that resemble differences seen in human studies of individuals with high and low risk for alcohol dependence. Recently, evidence of genes that affect event-related oscillations (EROs) and the risk for alcohol dependence has emerged, however, to date EROs have not been evaluated in genetic mouse models of high and low alcohol preference. Therefore, the objective of the present study was to characterize EROs in mouse models of high (C57BL/6 [B6] and high alcohol preference 1 [HAP-1] mice) and low (DBA/2J [D2] and low alcohol preference-1 [LAP-1] mice) alcohol preference. A time-frequency representation method was used to determine delta, theta and alpha/beta ERO energy and the degree of phase variation in these mouse models. The present results suggest that the decrease in P3 amplitudes previously shown in B6 mice, compared to D2 mice, is related to reductions in evoked delta ERO energy and delta and theta phase locking. In contrast, the increase in P1 amplitudes reported in HAP-1 mice, compared to LAP-1 mice, is associated with increases in evoked theta ERO energy. These studies suggest that differences in delta and theta ERO measures in mice mirror changes observed between groups at high- and low-risk for alcoholism where changes in EROs were found to be more significant than group differences in P3 amplitudes, further suggesting that ERO measures are more stable endophenotypes in the study of alcohol dependence. Further studies are needed to determine the relationship between expression of these neurophysiological endophenotypes and the genetic profile of these mouse models.

Event-related oscillations in mice: effects of stimulus characteristics

Event-related oscillations (EROs) are rhythmic changes that are evoked by sensory and/or cognitive processes that influence the dynamics of the EEG. EROs are estimated by a decomposition of the EEG signal into phase and magnitude information for a range of frequencies and then changes in those frequencies are characterized over a millisecond time scale with respect to task events. EROs have been demonstrated to be sensitive measures of both normal and abnormal cognitive functioning in humans but have not been fully described in mice. The results of these studies demonstrate that EROs can be generated in cortical sites in mice in the delta, theta, alpha/beta frequency ranges in response to auditory stimuli. Oscillations in the 7.5-40 Hz frequencies were significantly affected in the 0-50 ms time range in response to differences in tone frequency. Whereas, changes in tone loudness produced changes in oscillations in the 7.5-40 Hz frequencies in the 350-800 ms range. No significant changes in EROs were found to differences in tone probability. These studies suggest that EROs are an electrophysiological assay sensitive to tone characteristics and as such may be suitable for the exploration of the effects of genetic or neuropharmacological manipulations on neurosensory processing in mice.

Clinical course of alcohol dependence in African Americans

OBJECTIVE

The sequence and progression of alcohol related life events were investigated in a sample of African Americans and compared with findings from a predominantly Caucasian sample.

METHODS

Alcohol dependent participants were recruited from treatment facilities. Participants completed the Semi-Structured Assessment for the Genetics of Alcoholism to assess the physical, psychological and social manifestations of alcoholism and related disorders.

RESULTS

The sequence and mean age of appearance of alcohol-related life events were similar for this sample of African-American men and women. While there were similarities in the progression of alcohol related life problems between the African American and the Caucasian samples, the frequency of symptom endorsement for most problems was significantly higher in the Caucasian sample.

CONCLUSIONS

Identifying ethnic differences in the clinical course of alcohol dependence may be of importance in developing treatment plans and assist in the development of culturally sensitive intervention and prevention programs.

EEG spectral analysis in primary insomnia: NREM period effects and sex differences

STUDY OBJECTIVES

To compare NREM EEG power in primary insomnia (PI) and good sleeper controls (GSC), examining both sex and NREM period effects; to examine relationships between EEG power, clinical characteristics, and self-reports of sleep.

DESIGN

Overnight polysomnographic study.

SETTING

Sleep laboratory.

PARTICIPANTS

PI (n=48; 29 women) and GSC (n=25; 15 women).

INTERVENTIONS

None.

MEASUREMENTS

EEG power from 1-50 Hz was computed for artifact-free sleep epochs across four NREM periods. Repeated measures mixed effect models contrasted differences between groups, EEG frequency bands, and NREM periods. EEG power-frequency curves were modeled using regressions with fixed knot splines.

RESULTS

Mixed models showed no significant group (PI vs. GSC) differences; marginal sex differences (delta and theta bands); significant differences across NREM periods; and group*sex and group*NREM period interactions, particularly in beta and gamma bands. Modeled power-frequency curves showed no group difference in whole-night NREM, but PI had higher power than GSC from 18-40 Hz in the first NREM period. Among women, PI had higher 16 to 44-Hz power than GSC in the first 3 NREM periods, and higher 3 to 5-Hz power across all NREM periods. PI and GSC men showed no consistent differences in EEG power. High-frequency EEG power was not related to clinical or subjective sleep ratings in PI.

CONCLUSIONS

Women with PI, but not men, showed increased high-frequency and low-frequency EEG activity during NREM sleep compared to GSC, particularly in early NREM periods. Sex and NREM period may moderate quantitative EEG differences between PI and GSC.

Age-related differences in the blood alcohol levels of Wistar rats

Knowledge of blood alcohol levels (BALs) that are achieved following ethanol administration is critical for contemporary efforts to develop animal models of alcoholism. Adolescent and adult male Wistar rats were administered varying doses of ethanol (0.75, 1.5 and 3.0 g/kg) via gavage or intraperitoneal injection and BALs were measured over a two hour period. The results showed that adolescent animals had lower BALs across all time points in comparison to adults following administration of 0.75 g/kg ethanol and that 1 h after administration of 1.5 g/kg ethanol, adolescent animals showed an enhanced rate of elimination. The highest dose of ethanol (3.0 g/kg) produced comparable BALs for both adolescents and adults during the two-hour sampling period; however, the BALs for both ages were lower following administration of ethanol by gavage at this dose. Furthermore, an order effects analysis highlights that depending on the route of administration, initial dose size can influence the BALs produced by lower doses of ethanol. The current data identify the importance of measuring the level of alcohol in the blood to confirm that target BALs are achieved for adolescents and equivalent BALs are being reached for both adolescent and adult animals when such comparisons are made.

The clinical course of alcoholism in Trinidad and Tobago

OBJECTIVE

The clinical course of alcoholism has been described as a series of distinct, alcohol-related life events that occur in an orderly sequence. However, whether that sequence differs, depending on ethnicity and country of origin, is less clear. The purposes of this study were to investigate the sequence and progression of alcohol-related life events in individuals of East Indian (Indo) and African (Afro) heritage on the islands of Trinidad and Tobago, and compare those results with data reported previously by the Collaborative study for the Genetics of Alcoholism (COGA).

METHOD

Participants who were alcohol dependent (based on Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, criteria) and of Afro-Trinidadian and Tobagonian ancestry or Indo-Trinidadian ancestry were recruited from inpatient treatment facilities. A total of 148 alcohol-dependent men and women completed the Semi-Structured Assessment of the Genetics of Alcoholism, which assessed the physical, psychological, and social manifestations of alcohol dependence and other psychiatric disorders.

RESULTS

A high degree of similarity in the sequence of alcohol-related life events was found between Indo-Trinidadian, Afro-Trinidadian and Tobagonian, and COGA participants. However, Trinidadian and Tobagonian alcoholics were more likely to endorse severe alcohol drinking in the form of binges (2 or more days of intoxication), blackouts, withdrawal, and medical consequences; however, they were less likely to endorse aggressive acts associated with drinking. Progression to alcohol dependence was significantly slower in Trinidadian and Tobagonian alcoholics than in the U.S. population of alcoholics, but severe alcohol symptoms were more commonly endorsed in Trinidadian and Tobagonians.

CONCLUSIONS

Identifying ethnic and country of origin differences in the clinical course of alcohol dependence may assist in the development of culturally sensitive intervention and prevention programs.

Effects of adolescent ethanol exposure on sleep in adult rats

Although adolescent ethanol (EtOH) exposure has been associated with long-lasting changes in brain function, little is known as to whether EtOH exposure during adolescence alters sleep and cortical arousal. This study examined protracted alterations in sleep in adult rats exposed to EtOH during adolescence. Adolescent male Wistar rats were exposed to EtOH vapor for 12 h/day for 5 weeks. Cortical electroencephalograms were obtained during 4-h recording sessions after 5 weeks of withdrawal from EtOH. Adolescent EtOH exposure significantly reduced the mean duration of slow-wave sleep (SWS) episodes and the total amount of time spent in SWS in EtOH-exposed rats, compared to controls. Spectral analysis revealed that adolescent EtOH exposure significantly increased cortical peak frequencies during SWS in the 2-4, 4-6, and 6-8 Hz bands. Taken together, our findings suggest that chronic EtOH exposure in adolescent rats reduces measures of SWS, an effect also seen as part of normal aging. Although the cellular and molecular mechanisms mediating the consequences of EtOH exposure on the aging process are not known, the similarities between adolescent EtOH exposure and aging merits further investigation.

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.

Externalizing disorders in American Indians: comorbidity and a genome wide linkage analysis

Alcohol dependence is one of the leading causes of morbidity and mortality in Native Americans. Externalizing disorders such as conduct disorder (CD) and antisocial personality disorder (ASPD) have been demonstrated to have significant comorbidity with alcohol dependence in the general population. This study's aims were to: assess the comorbidity of DSM-III-R ASPD and CD with alcohol dependence, to map susceptibility loci for ASPD and CD, and to see if there is overlap with loci previously mapped for alcohol dependence phenotypes in 587 American Indians. Alcohol dependence was found to be comorbid with DSM-III-R ASPD but not CD. However, the amount of alcohol dependence in the population attributable to ASPD and/or CD is low. ASPD and the combined phenotype of participants with ASPD or CD were both found to have significant heritability, whereas no significant evidence was found for CD alone. Genotypes were determined for a panel of 791 micro-satellite polymorphisms in 251 of the participants. Analyses of multipoint variance component LOD scores, for ASPD and ASPD/CD, revealed six locations that had a LOD score of 2.0 or above: on chromosome 13 for ASPD and on chromosomes 1, 3, 4, 14, 17, and 20 for ASPD/CD. These results corroborate the importance of several chromosomal regions highlighted in prior segregation studies for externalizing diagnoses. These results also further identify new regions of the genome, that do not overlap with alcohol dependence phenotypes previously identified in this population, that may be unique to either the phenotypes evaluated or this population of American Indians.

Factors associated with remission from alcohol dependence in an American Indian community group

OBJECTIVE

This study identified factors associated with remission from DSM-III-R alcohol dependence in an American Indian community group.

METHOD

Participants were assessed by using the Semi-Structured Assessment for the Genetics of Alcoholism.

RESULTS

Five hundred eighty participants were assessed for alcohol use and alcohol use symptoms; 254 participants were found to have alcohol dependence. The rate of remission in this group was 59%. Thirty-four percent of remitters and 39% of nonremitters had received treatment for alcohol problems. Remission from alcohol dependence was associated with being female, older, and married; an earlier age of onset of alcohol dependence; and self-reported depression symptoms from drinking. Absence of remission was associated with continuing to drink despite knowing one had medical problems from drinking and self-reported anxiety symptoms from drinking.

CONCLUSIONS

Attention to factors associated with remission from alcohol dependence may be important in designing more effective treatment and prevention programs in this high-risk population.

Electrophysiological effects of dizocilpine (MK-801) in adult rats exposed to ethanol during adolescence

BACKGROUND

Despite evidence showing persistent changes in N-methyl-D-aspartate (NMDA)-receptor function following ethanol (EtOH) exposure, the contribution of NMDA systems to the long-term neurophysiological consequences of adolescent EtOH exposure is unclear. The aims of this study were the following: (1) to determine whether adolescent EtOH exposure produces neurophysiological changes after a prolonged withdrawal period in adult rats and (2) to assess protracted alterations in neurophysiological responses to the NMDA antagonist MK-801 in adult rats exposed to EtOH during adolescence.

METHODS

Adolescent male Wistar rats were exposed to EtOH vapor for 12 h/d for 5 weeks. The effects of MK-801 (0.0 to 0.1 mg/kg, intraperitoneally) on the electroencephalogram (EEG) and auditory event-related potentials (ERPs) were assessed after 8 weeks of abstinence from EtOH.

RESULTS

Experiments in aim 1 revealed that adolescent EtOH exposure reduced EEG variability in the frontal cortex in the 4 to 6 Hz band but had no effect on cortical and hippocampal EEG power and ERPs. Experiments in aim 2 showed that MK-801 significantly reduced EEG power in the parietal cortex (4 to 6 Hz, 6 to 8 Hz, 8 to 16 Hz, 16 to 32 Hz) and hippocampus (16 to 32 Hz) and EEG variability in the parietal cortex (6 to 8 Hz, 16 to 32 Hz) following adolescent EtOH exposure. MK-801 produced a significant decrease in hippocampal EEG variability (4 to 6 Hz, 8 to 16 Hz, 16 to 32 Hz) in control, but not in EtOH-exposed rats. MK-801 reduced frontal P1 ERP amplitude and latency in response to the rare tone in EtOH-exposed rats compared to controls. In contrast, MK-801 significantly reduced P3 ERP amplitude and latency in control, but not in EtOH-exposed rats.

CONCLUSIONS

The effects of MK-801 on hippocampal EEG variability and P3 ERP amplitude and latency are significantly attenuated after a prolonged withdrawal period following adolescent EtOH exposure. However, the inhibitory effects of MK-801 on cortical and hippocampal EEG power were enhanced in rats exposed to EtOH during adolescence. Taken together, these data suggest protracted changes in NMDA systems following adolescent EtOH exposure.

Addictions biology: haplotype-based analysis for 130 candidate genes on a single array

AIMS

To develop a panel of markers able to extract full haplotype information for candidate genes in alcoholism, other addictions and disorders of mood and anxiety.

METHODS

A total of 130 genes were haplotype tagged and genotyped in 7 case/control populations and 51 reference populations using Illumina GoldenGate SNP genotyping technology, determining haplotype coverage. We also constructed and determined the efficacy of a panel of 186 ancestry informative markers.

RESULTS

An average of 1465 loci were genotyped at an average completion rate of 91.3%, with an average call rate of 98.3% and replication rate of 99.7%. Completion and call rates were lowered by the performance of two datasets, highlighting the importance of the DNA quality in high throughput assays. A comparison of haplotypes captured by the Addictions Array tagging SNPs and commercially available whole-genome arrays from Illumina and Affymetrix shows comparable performance of the tag SNPs to the best whole-genome array in all populations for which data are available.

CONCLUSIONS

Arrays of haplotype-tagged candidate genes, such as this addictions-focused array, represent a cost-effective approach to generate high-quality SNP genotyping data useful for the haplotype-based analysis of panels of genes such as these 130 genes of interest to alcohol and addictions researchers. The inclusion of the 186 ancestry informative markers allows for the detection and correction for admixture and further enhances the utility of the array.

Association between single nucleotide polymorphisms in the mu opioid receptor gene (OPRM1) and self-reported responses to alcohol in American Indians

BACKGROUND

Variation in response to the hedonic and adverse effects of a substance is in part an inherited factor that may influence its use, abuse and dependence. The mu opioid receptor is the primary site of action for opiates and individuals with polymorphisms in this receptor appear to have variation in the CNS effects of opiates. Several studies have suggested that this receptor may also mediate some of the effects of non-opioid drugs, such as alcohol. The purpose of this study was to investigate associations between 13 single nucleotide polymorphisms in the mu opioid receptor gene (OPRM1) with self-reported responses to alcohol, an endophenotype associated with the development of alcohol dependence, in American Indians living on eight contiguous reservations.

METHODS

Each participant gave a blood sample and completed a structured diagnostic interview. Additionally, response to alcohol was indexed using the expectation version of the subjective high assessment scale (SHAS-E). SNPs were genotyped in 251 participants and data analyses were conducted using SOLAR.

RESULTS

The estimated heritability (h2) for the SHAS-E phenotypes ranged from 0.01 to 0.28. Endorsing the expectation of a more intense response on one or more of the following items from the SHAS-E: buzzed, clumsy, dizzy, drunk, effects, high, nausea, sleepy, talkative, terrible, and/or uncomfortable after imbibing 2-3 drinks was significantly associated with having at least one minor allele for at least one of 7 SNPs (p < 0.01) in the OPRM1 receptor gene.

CONCLUSION

These studies provide data to suggest that the minor allele, for most of the polymorphisms in the OPRM1 receptor gene investigated, was found to be associated with a more intense, and/or more adverse, response to alcohol, traits that are significantly correlated with lowered quantity of alcohol consumption and less susceptibility to dependence in this Indian population. These data further suggest that making conclusions on the role of the mu opiod receptor gene in the development of alcohol dependence may be limited if only one polymorphism in the gene is evaluated in isolation.

Dissociable effects of ethanol consumption during the light and dark phase in adolescent and adult Wistar rats

In adolescence, high levels of drinking over short episodes (binge drinking) is commonly seen in a proportion of the population. Because adolescence is an important neurodevelopmental period, the effects of binge drinking on brain and behavior has become a significant health concern. However, robust animal models of binge drinking in rats are still being developed and therefore further efforts are needed to optimize paradigms for inducing maximal self-administration of alcohol. In the present experiment, 1-h limited-access self-administration sessions were instituted to model excessive drinking behavior in adolescent and adult Wistar rats. In addition to age, the involvement of sex and phase within the light/dark cycle (i.e., drinking in the light or dark) on sweetened 5% ethanol intake were also evaluated over 14 limited-access sessions using a between-groups design. The results of the experiment showed that over 14 limited-access sessions, sweetened ethanol intake (g/kg) was significantly higher for adolescents compared to adults. Females were also found to drink more sweetened ethanol as compared to males. Additionally, drinking in the light produced a robust increase in sweetened ethanol intake (g/kg) in adolescents, as compared to adults during the light phase and as compared to both adolescent and adult rats drinking in the dark. Furthermore, the increase in ethanol consumption observed in adolescents drinking during the light phase was dissociable from sweetened solution intake patterns. These results identify that age, sex, and time of day all significantly influence consumption of sweetened ethanol in Wistar rats. Knowledge of these parameters should be useful for future experiments attempting to evaluate the effects of self-administered ethanol exposure in adult and adolescent rats.

P3 components of the event-related potential and marijuana dependence in Southwest California Indians

Native Americans have some of the highest rates of marijuana use and abuse, yet neurobiological measures associated with addiction to marijuana in this population remain unknown. The present investigation evaluated associations between the P350 and P450 components of the event-related potential (ERP) elicited by affective stimuli, and marijuana dependence in a population of Southwest California (SWC) Indian adults. Three hundred and seventeen participants with a mean age of 30 years who were free of major Axis I and psychiatric diagnoses and antisocial personality disorder were categorized as: (1) no marijuana use disorders or other drug dependence diagnoses; (2) marijuana dependence and no other drug dependence diagnoses; and (3) marijuana dependence and other drug dependence diagnoses. ERPs were collected using a facial discrimination task that generated a late positive component with two peaks at approximately P350 and P450 milliseconds. Multivariate analyses of variance was used to detect associations between the two component peaks and the three participant groups taking into consideration age, gender and the presence of a lifetime diagnosis of alcohol dependence. Increases in the latency of both the P350 and P450 component peaks were found to be associated with the diagnosis of marijuana dependence and marijuana dependence co-morbid with other drug dependence. Women appeared to be more impacted than men are. A diagnosis of marijuana dependence was not associated with any changes in late component amplitudes. Taken together these studies suggest that marijuana dependence may be associated with delays in the evaluation and identification of emotional stimuli in SWC Indians.

Sex differences in cardiac sympathovagal balance and vagal tone during nocturnal sleep

OBJECTIVE

To analyze sex differences in nocturnal vagal tone and cardiac sympathovagal balance during sleep in healthy men and women.

METHODS

In two groups of healthy, non-obese adults (15 men and 14 women), sleep was polygraphically recorded and heart rate variability was assessed during an awake period prior to sleep and during sleep. Vagal tone was estimated by the high-frequency (HF) power component of heart rate variability, and sympathovagal balance was indexed by the ratio of low-frequency (LF) power to HF power.

RESULTS

As compared to women, men showed decreases in vagal tone and increases in sympathovagal balance. During rapid eye movement (REM) sleep, a withdrawal of vagal tone occurred with an increase in sympathetic dominance. Men showed a greater increase of sympathovagal balance during REM sleep than women. Secondary analyses covarying for differences in reproductive hormone levels, physical activity, and sleep measures did not alter the results.

CONCLUSIONS

The marked increase in cardiac sympathetic drive during REM sleep in men has implications for understanding sex differences in the risk of cardiovascular events. Additionally, these data offer a pathway to explain the peak in cardiac arrhythmias and sudden cardiac death seen more often in the morning hours.

Differential effects of acute alcohol on EEG and sedative responses in adolescent and adult Wistar rats

Age-related developmental differences in sensitivity to the acute effects of alcohol may play an important role in the development of alcoholism. The present study was designed to evaluate the acute effects of alcohol on cortical electroencephalogram (EEG) in adolescent (P36) and adult (P78) Wistar rats. Five minutes of EEG was recorded after administration of 0, 0.75 or 1.5 g/kg alcohol. The righting reflex was performed to measure the sedative effects of alcohol (3.5 g/kg) and total sleeping time for each rat. Our results showed that alcohol (1.5 g/kg) increased power in the 1-2 Hz band and decreased the power in the 32-50 Hz band in the parietal cortical region of adolescent rats. Alcohol (1.5 g/kg) also increased stability of the EEG power in the slow-wave frequency bands (2-4 Hz, 4-6 Hz, and 6-8 Hz) of adolescent rats. In the frontal cortex of adult rats, but not in adolescent rats, alcohol (1.5 or 0.75 g/kg) decreased the power in the 16-32 Hz frequency band. Alcohol (1.5 g/kg) differentially increased power in a multiple of slow-wave frequency bands (2-4 Hz and 4-6 Hz) in the parietal cortex of adult rats as compared to adolescent rats. Adolescent rats were shown significantly shorter sleeping time and higher blood alcohol levels after regaining reflex than adult rats. Our results provide additional evidence of age-related differences in the effects of acute alcohol on cortical EEG, sedation and tolerance.

Association between single nucleotide polymorphisms in the cannabinoid receptor gene (CNR1) and impulsivity in southwest California Indians

Impulsivity is a personality trait characterized by acting suddenly in an unplanned manner in order to satisfy a desire without consideration for the consequences of such behavior. There are several psychiatric disorders that include the term impulsivity as a criterion and, therefore, it has been suggested that impulsivity may be an important phenotype that may link a number of different behavioral disorders, including substance abuse. This study's aims were to determine if a significant association could be detected between the (AAT)n triplet repeat polymorphism as well as 5 single nucleotide polymorphisms (SNPs) in or near the CNR1 receptor gene and impulsivity in Southwest California 'Mission' Indians (SWC). Impulsivity was assessed using a scale derived from the Maudsley personality inventory, and blood samples were collected for DNA analyses from 251 individuals recruited from local Indian reservations. The estimated heritability (h(2)) for the impulsivity phenotype was 0.20 + 0.12 (p < .004). Impulsivity was significantly associated with the 6-repeat allele of the triplet repeat polymorphism (AATn/A6; p < .0001), as well as four SNPs in or near the CNR1 receptor gene: rs1535255 (p = .001), rs2023239 (p = .004), rs1049353 (p < .001) and rs806368 (p < .0006). These studies provide data to suggest that the CNR1 receptor gene may be significantly associated with impulsivity in SWC Indians.