Effects of neuropeptide Y on appetitive and consummatory behaviors associated with alcohol drinking in wistar rats with a history of ethanol exposure

BACKGROUND

Neuropeptide Y (NPY) reduces ethanol intake under free access conditions in Wistar rats with a history of prolonged ethanol vapor exposure. The current study was designed to determine whether NPY differentially alters ethanol-associated appetitive behavior (i.e., lever pressing) or ethanol consumption in Wistar rats with a history of ethanol vapor exposure.

METHODS

Wistar rats were first trained to self-administer 10% ethanol in a paradigm that provided 25 min of free access to 10% ethanol after completing a 20-lever press response requirement (i.e., an RR20 schedule). After stable level lever pressing was established, operant sessions were suspended during a 9-week period of ethanol vapor exposure. Self-administration sessions were then reinstituted, and a fixed time (FT) schedule of 10% ethanol access was used to assess the effects of ethanol exposure and NPY on lever pressing and drinking behavior. Under the FT schedule, the maximum number of lever presses emitted within 10 min was assessed before providing access to 10% ethanol.

RESULTS

Ethanol vapor exposure did not alter patterns of lever pressing under the RR20 schedule, but lever presses emitted under the FT schedule were reduced after ethanol vapor exposure. Ethanol intake was significantly increased after ethanol vapor exposure. NPY significantly reduced ethanol intake but did not significantly reduce lever pressing under the FT schedule.

CONCLUSIONS

Taken together, these data suggest that chronic ethanol exposure increases ethanol intake without clearly enhancing its reinforcing value. Furthermore, NPY has a greater impact on the consummatory factors mediating ethanol intake than appetitive factors mediating ethanol seeking.

Effect of ethanol on brain neuropeptides in adolescent and adult rats

OBJECTIVE

Alcohol misuse early in life is associated with an increased risk of alcoholism. It is possible that this increased risk in adolescent drinkers is in part related to the susceptibility of the adolescent brain to ethanol. This study assessed the effects of ethanol exposure on several neuropeptides to begin to elucidate potential substrates that could mediate the differential effects of ethanol on adolescent and adult rats.

METHOD

Male Sprague Dawley rats were exposed to ethanol vapor or air during adolescence (30 days old, n = 9, controls = 8) or adulthood (80-90 days old, n = 9, controls = 8) for 10 days. Blood alcohol concentrations averaging 250 mg/dl were maintained during this period. After 7 weeks of cessation from ethanol vapor, brain tissue was collected from the frontal cortex, caudate, hippocampus, amygdala and hypothalamus to assess the immunoreactivity levels of neuropeptide Y (NPY-LI), corticotropin-releasing hormone, substance P (SP-LI) and neurokinins (NK-LI).

RESULTS

Ethanol exposure decreased overall hippocampal NPY-LI and increased SP-LI and NK-LI in the caudate, but these effects were more prominent in adult rats. Rats in the adult treatment groups (both ethanol exposed and controls) also had significantly lower levels of frontal cortical NK-LI, frontal cortical SP-LI and hypothalamic SP-LI relative to rats in the adolescent treatment groups.

CONCLUSIONS

These data indicate that brief exposure to alcohol has long-term effects on levels of NPY-LI, SP-LI and NK-LI. As these effects were primarily the result of changes in rats exposed to ethanol during adulthood, however, they are unlikely to contribute to the increased susceptibility of adolescents to the effects of chronic ethanol exposure.

Effect of social isolation on ethanol consumption and substance P/neurokinin expression in Wistar rats

Environmental factors, such as adverse life experiences and family/peer influences have a substantial influence on the development of disorders related to alcohol use. In animals, maternal or peer separation/isolation has been used as an environmental intervention that has been shown to alter neurodevelopment and influence drinking behaviors in rodents and primates. In this study, the effects of adult peer isolation on subsequent ethanol intake were investigated in Wistar rats. Because central tachykinin levels have been reported to differ between rats selected for enhanced ethanol preference, neuropeptide [neurokinin A (NKA), substance P (SP)] concentrations were also estimated. Lower levels of ethanol intake, in a two-bottle free-choice model, were observed on the first day of forced ethanol drinking in the single-housed animals. However, overall ethanol consumption was unaffected by peer isolation. Peer isolation significantly lowered SP and NKA levels in the hypothalamus, but this effect was not related to ethanol consumption or body weight. These data indicate that endogenous SP and neurokinin levels are reduced by isolation housing, but this was not associated with alterations in drinking levels using a two-bottle choice procedure.

EEG alpha variants and alpha power in Hispanic American and white non-Hispanic American young adults with a family history of alcohol dependence

Results from several studies support associations among variants in electroencephalogram (EEG) alpha voltage, alcohol dependence, ethnic heritage, and a family history of alcohol dependence, although no studies have as yet been conducted in individuals of Hispanic ethnicity. Categorization of EEG, by using spectral analyses, into high-, medium-, and low-voltage alpha, as well as absolute EEG power in alpha and beta frequency ranges, was carried out for Hispanic American (n=108) and white non-Hispanic American (n=269) young adult men and women (age range, 18 to 25 years) who had a family history, but no personal history, of alcohol dependence. Eighteen percent (n=70) of the participants were categorized as having a low-voltage alpha EEG, 16% had high-voltage alpha, and 64% had medium-voltage alpha. In comparison with findings for men, women were found to have higher overall power in the low frequency alpha (7.5-9 Hz) and beta (12-20 Hz, 20-50 Hz) frequency ranges. Hispanic Americans had a lower percentage of individuals in the low-voltage alpha group (9%) and more individuals in the medium-voltage alpha group (73%) compared with findings for white non-Hispanic Americans (low-voltage alpha, 19%; medium-voltage alpha, 62%). Results of the current study confirm the presence of ethnic stratification in EEG alpha variants.

Comorbidity of select anxiety and affective disorders with alcohol dependence in southwest California Indians

BACKGROUND

Native Americans, overall, have the highest prevalence of alcohol dependence of any US ethnic group. In several large national surveys, alcohol dependence has been significantly associated with higher rates of anxiety and affective disorders (comorbidity). However, the frequencies of these disorders and their comorbidity with alcohol dependence in Native American populations are relatively unknown.

METHODS

Demographic information and DSM-III-R diagnoses were obtained by using the Semi-Structured Assessment for the Genetics of Alcoholism developed for the Collaborative Study on the Genetics of Alcoholism from 483 Southwest California Indian adults residing on contiguous reservations. The Semi-Structured Assessment for the Genetics of Alcoholism allowed differentiation of each anxiety and affective disorder into one of three types: independent of substance use, concurrent with alcohol use, and concurrent with drug use.

RESULTS

Sixty-six percent of the men and 53% of the women sampled had a lifetime diagnosis of alcohol dependence. Fourteen percent of the sample had a lifetime independent anxiety disorder, and 14% of the sample had a lifetime independent affective disorder. Alcohol- and/or drug-concurrent major depression occurred in 8%, and other alcohol- and/or drug-concurrent anxiety and affective disorders each occurred in less than 1.1% of the sample. No significant comorbidity was found between alcohol dependence and independent agoraphobia, social phobia, or major depressive disorder.

CONCLUSIONS

In this Southwest California Indian sample, rates of anxiety and affective disorders were substantially similar to those reported in the National Comorbidity Survey; however, comorbidity of independent disorders with alcohol dependence was not as pervasive as in the National Comorbidity Survey. Rates of concurrent anxiety and affective disorders were low. These data support the hypothesis that despite high rates of alcohol dependence, Southwest California Indians do not have higher rates of anxiety and affective disorders or comorbidity of these disorders with alcohol dependence than those reported in large surveys of non-American Indian populations.

Associations of ALDH2 and ADH1B genotypes with response to alcohol in Asian Americans

OBJECTIVE

Individuals with alcohol dependence are less likely to possess variant alleles of the alcohol-metabolizing genes, aldehyde dehydrogenase (ALDH2*2) and alcohol dehydrogenase (ADH1B*2), than non-alcohol-dependent controls. It is hypothesized that the mechanism through which these alleles protect against alcohol dependence is by causing elevations in acetaldehyde, which in turn cause an increased response to alcohol. Previous research has shown that individuals with ALDH2*2 demonstrate enhanced reactions to alcohol compared with those without this genetic variant, but evidence that ADH1B*2 is associated with a greater alcohol response is mixed. This study was designed to determine whether the ADH1B genotype is associated with more intense reactions to alcohol after controlling for the ALDH2 genotype.

METHOD

Participants (N = 101) were Asian American college students. Each was evaluated using objective and subjective measures before and after ingestion of alcohol and placebo beverages.

RESULTS

Participants with the ALDH2*1/*2 and ALDH2*2/*2 genotypes were more likely to experience vomiting following ingestion of the alcohol beverage than those with the ALDH2*1/*1 genotype. Participants with the ALDH2*1/*2 genotype also had greater pulse-rate increases, observed flushing ratings, and subjective feelings of intoxication 30 minutes after ingestion of alcohol than participants with the ALDH2*1/*1 genotype, despite equivalent blood alcohol concentration (BAC) measurements. Among participants with the ALDH2*1/*1 genotype, there were no additional effects of the ADH1B genotype on any measures of response to alcohol. Among participants with the ALDH2*1/*2 genotype, those with the ADH1B*2/*2 genotype were more likely to experience alcohol-induced vomiting and to report feeling less "great overall" 30 minutes after ingestion of alcohol than those with the ADH1B*1/*2 genotype.

CONCLUSIONS

These findings are consistent with the hypothesis that there is an additional effect of ADH1B*2 on level of response to alcohol, but only among individuals with the ALDH2*1/*2 genotype.

Effects of neuropeptide Y and corticotropin-releasing factor on ethanol intake in Wistar rats: interaction with chronic ethanol exposure

Neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) have opposing effects on stress-associated and consummatory behaviors in rodents. Recent studies also suggest that both peptides influence ethanol intake. In the present study, the effects of administration of CRF and NPY into the lateral ventricle on ethanol intake in naive and ethanol-vapor-exposed Wistar rats were examined. A limited access paradigm was used to measure intake of a 10% (v/v) ethanol solution in Wistar rats trained to drink using a sucrose fading procedure. Ethanol vapor exposure for 8 weeks significantly elevated ethanol intake in this limited access paradigm relative to pre-exposure levels. The effects of icv administration of CRF (1 microg), NPY (10 microg) or NPY/CRF combined (10 and 1 microg, respectively) on ethanol intake were then assessed. In non-vapor-exposed subjects, icv infusion of NPY had no effect on ethanol intake, while a significant suppression of drinking was seen following icv administration of CRF. Administration of NPY in combination with CRF had no effect on ethanol intake in non-ethanol-vapor-exposed rats. In vapor-exposed subjects, both NPY and CRF reduced ethanol intake, but when given in combination, no difference from vehicle was detected. Locomotor activity was measured during drinking sessions and was unaffected by peptide administration. These studies underscore the importance of a history of exposure to chronic ethanol vapor in the regulation of ethanol intake by NPY. Furthermore, the results presented here suggest that a balance between the stress-related peptides NPY and CRF may be involved in the regulation of ethanol intake.

Association of ALDH1 promoter polymorphisms with alcohol-related phenotypes in southwest California Indians

BACKGROUND

Cytosolic aldehyde dehydrogenase (ALDH1A1) is an important enzyme in the metabolism of acetaldehyde and the synthesis of retinoic acid. Two polymorphisms in the promoter region of ALDH1A1-ALDH1A1*2 and ALDH1A1*3-have recently been identified and described in small samples of Asian, Caucasian, and African individuals. The aim of this study was to determine the prevalence of these polymorphisms in a sample of Southwest California Indians and to test for associations with alcohol dependence and other substance-related behaviors.

METHODS

The participants in this study were 463 adult men and women recruited from 8 contiguous Indian reservations. A structured interview was used to gather information on demographics, psychiatric diagnoses, and personal drinking and drug use history. A blood sample was obtained from each participant, and leukocyte DNA was extracted and used to genotype for the presence of the ALDH1A1 promoter polymorphisms.

RESULTS

Twenty-seven participants (6%) possessed ALDH1A1*2 (frequency, 0.03), two participants possessed ALDH1A1*3, and one participant displayed both of these alleles. Individuals with an ALDH1A1*2 allele had lower rates of alcohol dependence and regular tobacco use than those without this allele. Individuals with ALDH1A1*2 also reported a significantly lower maximum number of drinks ever consumed in a 24-hr period, reported drinking fewer drinks per occasion when they first started drinking regularly, and reported lower expectations of alcohol's effects compared with individuals without this allele.

CONCLUSIONS

Results from this study suggest that ALDH1A1*2 may be associated with protection from the development of alcohol and other substance use disorders.

Electrophysiological Effects of Allopregnanolone in Rats With a History of Ethanol Exposure

BACKGROUND

Sensitivity to the anticonvulsant effects of allopregnanolone (ALLO) is enhanced during the early phase of ethanol (EtOH) withdrawal. However, it is unclear whether this enhanced sensitivity generalizes to ALLO's neurobehavioral effects during protracted abstinence. The purpose of this study was to examine the neurophysiological effects of ALLO in rats with a history of chronic EtOH exposure after a protracted period of abstinence.

METHODS

Male Wistar rats were exposed to EtOH vapor for 14 hr/day for 5 weeks. Blood EtOH levels were maintained between 200 and 250 mg/dl. The effects of ALLO (0.0-10 mg/kg, intraperitoneally) on motor activity, the electroencephalogram (EEG), and auditory event-related potentials then were assessed after 6 to 8 weeks of abstinence from EtOH.

RESULTS

ALLO's effects on the EEG were consistent with previous studies and were unaffected by EtOH exposure. ALLO increased high-frequency EEG power and shifted peak EEG frequencies in a benzodiazepine- and barbiturate-like manner in both the cortex and the hippocampus. The effects of ALLO on event-related potentials were attenuated in rats with a history of EtOH exposure. Low doses of ALLO (1 and 5 mg/kg) reduced cortical P1 amplitude in response to the standard tone but only in the control group. ALLO also increased N1 amplitude in the hippocampus of the control group while having no significant effect in EtOH-exposed rats. Low doses of ALLO (1 and 5 mg/kg) were found to increase motor activity.

CONCLUSIONS

These data indicate that a history of EtOH exposure attenuates some of the neurophysiological effects of ALLO in a manner consistent with cross-tolerance. Taken together, these data suggest that increased sensitivity to ALLO's neurobehavioral effects is limited to the early phases of EtOH withdrawal and may not extend to more protracted periods of abstinence.

Neurophysiologic consequences of neonatal ethanol exposure in the rat

Many of the neurotoxic and neurobehavioral consequences of neonatal ethanol exposure in the rat have been characterized. However, in few studies has adult neurophysiologic function been assessed in rats exposed to ethanol during this key developmental period. In the current study, the effects of neonatal ethanol exposure on adult electroencephalographic (EEG) activity and auditory event-related potentials (ERPs) were examined in the rat. Male Sprague-Dawley rats were exposed to ethanol at 6.0 g/kg/day between postnatal days 4 through 9 by using an artificial-rearing procedure. Two control groups were used: a suckle control (SC) group and a gastrostomized control (GC) group. After reaching adulthood (i.e., at 3.5-4 months old), recording electrodes were implanted into the brain of each rat, so that EEG activity and auditory ERPs from the cortex and hippocampus could be assessed. Rats exposed to ethanol during the neonatal period were hyperactive as adults. Assessment of the EEG activity revealed that ethanol exposure increased peak frequency in the frontal cortical and parietal cortical 16-32 Hz frequency bands. Assessment of ERPs revealed that parietal cortical N1 amplitude was reduced in ethanol-exposed rats. Furthermore, parietal cortical N1 latency was increased in the GC group. These findings demonstrate that enhanced motor activity in rats exposed to ethanol during neonatal development occurs in combination with EEG indices of enhanced cortical and hippocampal arousal. Furthermore, a deficiency in cortical N1 amplitude indicates adult rats may have attention deficits. Overall, these results indicate that neonatal ethanol exposure has enduring neurobehavioral consequences, which persist into adulthood. This neurobehavioral profile in the rat is consistent with clinical observations of attention deficits and hyperactivity in children exposed to ethanol during prenatal development.

Long-term neurobehavioral effects of alcohol or nicotine exposure in adolescent animal models

Adolescent alcohol and nicotine abuse is common, but its neurodevelopmental consequences remain unclear. This laboratory utilized adolescent rodent models to assess the hypothesis that adolescents are highly susceptible to the effects of alcohol and nicotine. Rats were exposed to ethanol for 10-14 days using an intermittent vapor inhalation paradigm. Rats were continuously exposed to nicotine for 5 days using Nicoderm CQ transdermal patches. Alcohol or nicotine exposure altered neurobehavioral function when assessed after 3-7 weeks of abstinence. Alcohol-induced changes include increased electroencephalographic (EEG) frequency, decreased amplitude of the cortical N1 and hippocampal P3 event-related potential (ERP) components, enhanced anxiety-like behavior, and enhanced depressive-like behavior. Nicotine-induced changes include decreased slow-wave cortical EEG power, increased cortical N1 ERP amplitude, decreased motor activity, and increased anxiety-like behavior. These findings support the hypothesis that adolescents are uniquely susceptible to the effects of chronic alcohol and nicotine exposure.

Genomic screen for loci associated with alcohol dependence in Mission Indians

Alcohol dependence is a leading cause of morbidity and mortality in Native Americans, yet biological factors underlying the disorder in this ethnic group remain elusive. This study's aims were to map susceptibility loci for DSM-III-R alcohol dependence and two narrower alcohol-related phenotypes in Mission Indian families. Each participant gave a blood sample and completed an interview using the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) that was used to make alcohol dependence diagnoses and the narrower phenotypes of withdrawal, and drinking severity. Genotypes were determined for a panel 791 microsatellite polymorphisms. Analyses of multipoint variance component LOD scores for the dichotomous DSM-III-R phenotype revealed no peak LOD scores that exceeded 2.0 at any chromosome location. Two chromosomes, 4 and 12, had peak LOD scores that exceeded 2 for the alcohol use severity phenotype and three chromosomes 6, 15, 16 were found to have peaks with LOD scores that exceeded 2 for the withdrawal phenotype. Evidence for linkage to chromosomes 4 and 15, and 16 have been reported previously for alcohol related phenotypes whereas no evidence has as yet been reported for chromosomes 6 and 12. Combined linkage and association analysis suggest that alcohol dehydrogenase 1B gene polymorphisms are partially responsible for the linkage result on chromosome 4 in this population. These results corroborate the importance of several chromosomal regions highlighted in prior segregation studies in alcoholism and further identify new regions of the genome that may be unique to either the restricted phenotypes evaluated or this population of Mission Indians.

The clinical course of alcoholism in 243 Mission Indians

OBJECTIVE

This study was conducted to describe the order of appearance and the progression of alcohol-related life events in Mission Indian men and women with a lifetime diagnosis of alcohol dependence.

METHOD

A total of 407 participants completed a structured interview that gathered information on alcohol diagnoses, remissions, abstinences, and treatments as well as alcohol-related life events.

RESULTS

A total of 70% of the men and 50% of the women sampled met lifetime diagnostic criteria for alcohol dependence. The age at onset of alcohol dependence was younger (20 years) and the course proceeded more rapidly (6 years) than what has been described in other large studies of alcoholics. A high degree of similarity in the type and progression of alcohol-related life events was found between Mission Indian men and women and alcoholics from the Collaborative Study on the Genetics of Alcoholism (COGA). However, Mission Indians in this study were significantly more likely than alcoholics in the COGA to experience binge drinking, physical fighting, driving while intoxicated, and alcohol-related health problems and were less likely to consider themselves excessive drinkers, drinking where and when they had not intended to, and to experience guilt concerning their drinking. Rates of abstention after an alcohol dependence diagnosis (61%) and remission from alcohol dependence symptoms (77%) were also high in Mission Indians.

CONCLUSIONS

Understanding the course of Mission Indian alcoholism can help identify unique alcohol-related phenotypes as well as guide the development of treatment and prevention programs in this underserved population.

Evaluation of aldehyde dehydrogenase 1 promoter polymorphisms identified in human populations

BACKGROUND

Cytosolic aldehyde dehydrogenase, or ALDH1A1, functions in ethanol detoxification, metabolism of neurotransmitters, and synthesis of retinoic acid. Because the promoter region of a gene can influence gene expression, the ALDH1A1 promoter regions were studied to identify polymorphism, to assess their functional significance, and to determine whether they were associated with a risk for developing alcoholism.

METHODS

Sequence analysis was performed in the promoter region by using Asian, Caucasian, and African American subjects. The resulting polymorphisms were assessed for frequency in Asian, Caucasian, Jewish, and African American populations and tested for associations with alcohol dependence in Asian and African American populations of alcoholics and controls. The functional significance of each polymorphism was determined through in vitro expression analysis by using HeLa and HepG2 cells.

RESULTS

Two polymorphisms, a 17 base pair (bp) deletion (-416/-432) and a 3 bp insertion (-524), were discovered in the ALDH1A1 promoter region: ALDH1A1*2 and ALDH1A1*3, respectively. ALDH1A1*2 was observed at frequencies of 0.035, 0.023, 0.023, and 0.012 in the Asian, Caucasian, Jewish, and African American populations, respectively. ALDH1A1*3 was observed only in the African American population, at a frequency of 0.029. By using HeLa and HepG2 cells for in vitro expression, the activity of the luciferase reporter gene was significantly decreased after transient transfection of ALDH1A1*3-luciferase compared with the wild-type construct ALDH1A1*1-luciferase. In an African American population, a trend for higher frequencies of the ALDH1A1*2 and ALDH1A1*3 alleles was observed in a population of alcoholics (p = 0.03 and f = 0.12, respectively) compared with the control population.

CONCLUSIONS

ALDH1A1*2 and ALDH1A1*3 may influence ALDH1A1 gene expression. Both ALDH1A1*2 and ALDH1A1*3 produce a trend in an African American population that may be indicative of an association with alcoholism; however, more samples are required to validate this observation. The underlying mechanisms contributing to these trends are still unknown.

EEG alpha and level of response to alcohol in Hispanic- and non-Hispanic-American young adults with a family history of alcoholism

OBJECTIVE

A person's level of response to alcohol is associated with family history of alcoholism, ethnic heritage and electroencephalogram (EEG) phenotype. The present study's aims were to investigate EEG alpha and response to alcohol in Hispanic-American and non-Hispanic-American young adults.

METHOD

EEG power in the slow and fast alpha frequency ranges (7.5-9 Hz, 9-12 Hz) was obtained at baseline and at 74 minutes following the administration of alcohol to Hispanic-American (n = 79) and white non-Hispanic-American (n = 208) young adult men and women (18-25 years old), all of whom had a family history but no personal history of alcohol dependence. Measures of breath alcohol concentrations and subjective responses to alcohol (Subjective High Assessment Scale [SHAS]) also were ascertained.

RESULTS

Alcohol was found to produce significant effects on EEG power in the slow (F = 79.5, p < .0001) alpha frequency range. Although no overall effects of alcohol were found in the fast alpha frequency range, Hispanic participants had decreases in EEG fast alpha activity following alcohol administration, whereas non-Hispanics had alcohol-induced increases in power in this frequency range (F = 4.0, p < .04). EEG power, in the fast alpha frequency range (9-12 Hz) at baseline, also was found to be negatively associated with level of response to alcohol, as indexed by SHAS scores (F = 5.2, 2/283 df, p < .023).

CONCLUSIONS

Previous studies in Native Americans, Asians and Euro-Americans have suggested genetic stratification in EEG response to alcohol as well as significant associations with family history of alcoholism. The present results extend previous studies to Hispanics and further confirm that increased EEG alpha power at baseline is predictive of a less intense response to alcohol, as indexed by the SHAS.

Spectral analyses of sleep EEG in depressed offspring of fathers with or without a positive history of alcohol abuse or dependence: a pilot study

The current study was designed to examine the effects of family history of alcohol use disorders on spectral electroencephalographic (EEG) sleep measures obtained in a sample of youth with depression. We evaluated sleep in 32 depressed youth (8-16 years of age) with and without a family history of alcohol use disorders. Eighteen of the participants (10 males and 8 females) reported a positive paternal history of alcohol use disorders and made up the family history positive (FHP) group. Power-spectral analyses revealed that increased power in the 7.50-11.00 Hz band (slow alpha) was associated with boys in the FHP group for the first and second non-rapid eye movement (REM) periods, second REM period, awake during the night, and entire night period. Results also showed increased power in the higher alpha frequencies (11.00-12.25 Hz) for non-REM, REM, and awake periods. A significant increase in spectral power was also observed in boys in the FHP group in the delta frequencies (0.75-4.50 Hz) during the second REM period. These findings are consistent with results from previous studies, demonstrating that EEG alpha power is positively associated with a family history of alcohol use disorders.

Event-related potential responses to alcohol-related stimuli in African-American young adults: relation to family history of alcoholism and drug usage

AIMS

To use event-related potentials (ERPs) to investigate the response to alcohol-related stimuli in African-American young adults.

METHODS

ERPs to an object recognition task, that included pictures of objects, food and alcohol-related and non-alcohol-related drinks as stimuli, were obtained in 81 African-American young adult men and women (18-25 years old) without a personal history of alcohol dependence. Information on: psychiatric diagnoses, personal drinking and drug use history, and familial history of alcoholism was also obtained.

RESULTS

Family history was found to be associated with lowered P3 components and higher N1 components in response to the non-alcohol-related drinks. Additionally, an exploratory analyses revealed that lower amplitude N1 components were generated in response to alcohol-related stimuli in regular marijuana users compared with non-regular users. No associations of N1 or P3 amplitudes with conduct disorder symptoms or current drinking status were found in this population.

CONCLUSIONS

These studies demonstrated that family history is significantly and selectively associated with lower P3 amplitudes in this group of young adult men and women of African-American heritage. Additionally, current usage of marijuana and alcohol do not modify P3 amplitudes. However, regular marijuana use may diminish N1 response to alcohol-related stimuli, whereas, family history of alcoholism may augment N1 responses. Taken together these studies further suggest that ERPs can provide specific information on alcoholism risk as well as use of other misused drugs.

EEG low-voltage alpha and alpha power in African American young adults: relation to family history of alcoholism

BACKGROUND

Several studies support an association between having a low-voltage EEG and alcohol dependence; however, it is not clear whether this measure represents a risk marker or is a result of years of heavy drinking. The present study's aims were to investigate the prevalence of low-voltage alpha EEG variants in African American young adults who have not yet developed alcohol dependence and to test for associations between low-voltage alpha (LVA) EEG, alpha power, and a family history of alcohol dependence.

METHODS

Clinical ratings and spectral characteristics of the EEG, collected using bipolar recordings, were investigated in 81 African American young adult men and women (18-25 years old) who had no personal history of alcohol dependence. Information on psychiatric diagnoses, personality features, personal drinking and drug use history, and family history (FH) of alcoholism was obtained.

RESULTS

Thirty-two percent (n = 26) of the participants had an LVA EEG variant, and an additional 22% (n = 18) had borderline LVA. The presence of an LVA variant was not associated with drinking status, a family history of alcoholism, or a personal history of anxiety disorders but was associated with significantly higher extroversion scores. Participants who had an FH of alcoholism had significantly higher spectral power in the slow alpha frequencies (7.5-9 Hz). FH was not associated with any significant differences in any other EEG frequency band.

CONCLUSIONS

These findings suggest that considerable ethic variation may exist in the prevalence of LVA EEG variants. In addition, like findings in other populations of non-African descent, having an FH of alcohol dependence may be associated with significantly higher voltage in the alpha frequency ranges.

Increased anxiety-like behavior in adult rats exposed to nicotine as adolescents

OBJECTIVE

Twenty percent of adolescents between 12 and 18 years old are regular smokers. Recently developed animal models demonstrate that adolescent nicotine exposure produces behavioral and electrophysiological changes, which persist into adulthood. The purpose of this study was to further define the behavioral effects of nicotine exposure during adolescence.

METHODS

Male 31-36-day-old adolescent rats were administered 5.0 mg/kg/day nicotine using transdermal Nicoderm CQ patches (SmithKline Beecham). During nicotine exposure, motor activity was assessed. Behavior in both standard open field and modified open field was examined 2-3 weeks after exposure ended.

RESULTS

Nicotine exposure significantly enhanced motor activity in nicotine-exposed rats compared with controls, demonstrating the acute stimulatory effects of transdermal nicotine. Two to three weeks after nicotine exposure ended, significantly lower levels of exploratory activity were observed relative to controls in the standard open field. Rats exposed to nicotine during adolescence also retreated to the perimeter of the open field more quickly than control rats. In a modified open field, nicotine exposure reduced approaches to food, contact with food and food intake.

CONCLUSIONS

Taken together, these data suggest that adolescent nicotine exposure may induce an anxiogenic profile, which persists beyond acute nicotine withdrawal. Given the hypothesized role of stress and anxiety in the maintenance of smoking, it could be speculated that anxiety associated with smoking abstinence may play an important role in continued adolescent tobacco use.

Association of the ADH2*3 allele with greater alcohol expectancies in African-American young adults

OBJECTIVE

A polymorphism at the alcohol dehydrogenase (ADH) gene locus, ADH2*3, exhibits markedly greater capacity and maximal velocity for ethanol, and has been reported to occur exclusively in African Americans and some tribes of Native Americans. While it appears that this allele may produce protection from alcohol-induced morbidity, the mechanism by which it does so remains unknown.

METHOD

This study examined the association between expectations of the effects of alcohol and the presence of the ADH2*3 allele in 66 African-American young adults (18-25 years old). A structured interview, alcohol-related expectancies and a blood sample were obtained from each participant.

RESULTS

A positive association between the presence of an ADH2*3 allele and expectations of alcohol's effects (p < .01) was uncovered.

CONCLUSIONS

These data suggest that the ADH2*3 allele may encode for a more intense response to alcohol, an effect associated with protection from the development of alcohol-use disorders in other populations.

The effects of corticotropin-releasing factor on the cortical EEG are reduced following adolescent nicotine exposure

Although smoking is highly prevalent among adolescents, relatively little is known about the lasting neurobehavioral consequences associated with adolescent nicotine exposure. Prior studies from our laboratory suggest that adolescent nicotine exposure induces an anxiogenic profile in adult rats. Corticotropin-releasing factor (CRF) systems are important modulators of anxiety and response to stress. Since acute nicotine administration has been shown to stimulate central CRF activity, the purpose of this study was to examine the effects of adolescent nicotine exposure on CRFs modulation of the cortical and hippocampal EEG in adult rats. Male Sprague-Dawley rats were exposed to nicotine (5 mg/kg/day) between postnatal days 35-40 using transdermal nicotine patches. Six weeks after nicotine exposure ended, the effects of intracerebroventricular administration of CRF (0.01-1.0 microg/5 microl) on EEG activity in the cortex and hippocampus were assessed in nicotine-exposed rats and age-matched control rats. The overall effects CRF were consistent with previous reports. CRF decreased low to moderate frequency EEG activity (1-32 Hz) and increased high frequency EEG activity (32-50 Hz). However, in nicotine-exposed rats the effects of CRF on the frontal and parietal cortical EEG were blunted by 30-50% compared to control rats. A similar pattern of decreased response to CRF was not observed in the hippocampus. These blunted effects of CRF on the cortical EEG suggest that long-term changes in systems responsive to CRF result from adolescent nicotine exposure. Given the role of CRF systems in behavioral responses to stress and anxiety, these data suggest that adolescent nicotine exposure may produce long-term decreases in neurophysiological responses to stress.

EEG and ERP profiles in the high alcohol preferring (HAP) and low alcohol preferring (LAP) mice: relationship to ethanol preference

Neurophysiological measures, such as decreased P300 amplitude and altered EEG alpha activity, have been associated with increased alcoholism risk. The purpose of the present study was to extend the assessment of the neurophysiological indices associated with alcohol consumption to a recently developed mouse model of high ethanol consumption, the first replicate line of high alcohol preferring (HAP-1) and low alcohol preferring (LAP-1) mice. Male HAP-1, LAP-1, and HS mice from the Institute for Behavioral Genetics at the University of Colorado Health Science Center (i.e., HS/Ibg mice) were implanted with cortical electrodes. EEG activity, and event related potentials (ERPs) were then examined. Following electrophysiological assessment, ethanol preference was assessed to examine the relationship between neurophysiological indices and ethanol consumption. EEG analyses revealed that HAPs and HS/Ibgs had greater peak frequency in the 2-4-Hz band and lower peak frequency in the 6-8- and 1-50-Hz bands of the cortical EEG compared to LAPs. Compared to HAPs, LAPs and HS/Ibgs had decreased peak EEG frequency in the 8-16-Hz band. Decreased parietal cortical power from 8 to 50 Hz was associated with high initial ethanol preference in HAP mice. In regards to ERPs, P1 amplitude was greater in HAPs compared to both LAPs and HS/Ibgs and the P3 latency in LAPs was decreased compared to both HAPs and HS/Ibgs. As expected, HAPs consumed more ethanol and had higher ethanol preference than LAPs and HS/Ibgs. There were no significant differences in ethanol intake or preference between HS/Ibgs and LAPs. These data indicate that selective breeding of the HAP and LAP lines has resulted in the divergence of EEG and ERP phenotypes. The differences observed suggest that increased cortical P1 amplitude and altered cortical EEG activity in the 8-50-Hz frequency range may be neurophysiological 'risk factors' associated with high ethanol consumption in mice. Decreased P3 latency in LAPs compared to HAPs and HS/Ibgs mice may be a 'protective factor'.

Protective association of genetic variation in alcohol dehydrogenase with alcohol dependence in Native American Mission Indians

OBJECTIVE

Two alcohol dehydrogenase genes (ADH2 and ADH3 on chromosome 4) and one aldehyde dehydrogenase gene (ALDH2 on chromosome 12) exhibit functional polymorphisms. The goal of this study was to determine whether any associations exist between the ADH2, ADH3, and ALDH2 polymorphisms and alcohol dependence in a group of Native Americans. An additional goal was to determine if any associations exist between these polymorphisms and the endophenotype, maximum number of drinks ever consumed in a 24-hour period.

METHOD

Mission Indian adults (N=340) were recruited for participation from reservations in southern California. Each participant completed an interview with the Semi-Structured Assessment for the Genetics of Alcoholism. A blood sample was collected from each participant for genotyping at the ALDH2, ADH2, and ADH3 loci.

RESULTS

Sixty percent of all participants (72% of men and 53% of women) met lifetime DSM-III-R criteria for alcohol dependence. A significant difference in the ADH2 allele distributions was found between alcohol-dependent and non-alcohol-dependent participants. Those with alcohol dependence were significantly less likely to have the ADH2*3 allele (odds ratio=0.28) and significantly more likely to have the ADH2*1 allele (odds ratio=2.00) than those who were not alcohol dependent. Individuals with ADH2*3 reported a lower number of maximum drinks ever consumed in a 24-hour period, compared to those without this allele.

CONCLUSIONS

These results are consistent with genetic linkage studies showing protective associations for alcohol dependence and related behavior on chromosome 4 and suggest that ADH2 polymorphisms may account for these findings. These results also highlight the utility of evaluating protective factors in populations with high rates of alcohol dependence.

Long latency event-related potentials in mice: effects of stimulus characteristics and strain

The P3, or P300 component of the event-related potentials (ERPs) is a positive going waveform that can be averaged from the EEG approximately 250-500 ms following the presentation of task or context 'relevant' stimuli. This potential has been demonstrated to be a sensitive measure of both normal and abnormal cognitive functioning. P300 models have been developed in monkeys, cats and rats. The aim of the present study was to develop an auditory ERP paradigm suitable for use in mice that resembled those used in humans and other animal models. The results of the studies showed that late positive potentials in the 200-400 ms range could be generated in cortical sites in response to auditory stimuli. Additionally, like passive ERPs recorded in humans, mouse ERPs were sensitive to changes in stimulus characteristics. An earlier negative component designated the N1 was found to be sensitive to tone frequency and loudness but not to stimulus probability, whereas the mouse P300 component was sensitive to probability but not to tone frequency or loudness. C57BL/6 mice, a strain known to have a strong alcohol preference, were found to have significantly lower P300 amplitudes when compared to the DBA/2 strain. These findings also parallel human studies, and studies of selected lines of rats, demonstrating that decrements in P300 amplitude can be associated with a genetic vulnerability to alcoholism/alcohol preference. These studies further suggest that ERPs are an electrophysiological assay suitable for the exploration of the effects of genetic manipulations on neurosensory processing in mice.

Neurophysiological profiles of replicate line 2 high-alcohol-drinking (HAD-2) and low-alcohol-drinking (LAD-2) rats

RATIONALE

A select number of electrophysiological findings have been demonstrated to differentiate rat lines selectively bred for high and low ethanol preference.

OBJECTIVE

In the present study, EEGs and event-related potentials (ERPs) of high-alcohol-drinking (HAD) and low-alcohol-drinking (LAD) rats from replicate line 2 (HAD-2 and LAD-2) were assessed to determine if their neurophysiological profiles are similar to selected lines previously evaluated.

METHODS

Rats obtained from Indiana University were implanted with cortical and amygdalar recording electrodes. Baseline EEG and ERPs were assessed in ethanol-naïve HAD-2 and LAD-2 rats. Animals subsequently were trained to self-administer ethanol by using a sucrose-substitution procedure.

RESULTS

Compared with LAD-2 rats, HAD-2 rats displayed greater parietal cortical power in the 6 to 32 Hz frequency range of the EEG. Greater parietal cortical peak frequency in the 2 to 4 Hz range and decreased frontal, parietal, and amygdalar peak frequencies in the 16 to 32 Hz frequency range were also seen. Compared with LAD-2 rats, HAD-2 rats had decreased P2 latency of ERPs recorded in the parietal cortex. HAD-2 rats also had greater frontal, parietal, and amygdalar P2 amplitudes, greater frontal and parietal cortical P1 amplitudes, and greater parietal cortical P3 amplitudes compared with LAD-2 rats. As anticipated, HAD-2 rats consumed significantly greater levels of sucrose, sucrose-ethanol, and ethanol over the course of the sucrose-substitution procedure compared with LAD-2 rats.

CONCLUSIONS

These data suggest that increased cortical power is associated with high ethanol preference in a number of selectively bred rat lines. However, unique electrophysiological characteristics may index alcohol preference in each line.