Central nervous system serotonin and personality as variables contributing to excessive alcohol consumption in non-human primates

The Relation between Plasma Nesfatin-1 Levels and Aggressive Behavior in Pit Bull Dogs

Aggression is a prevalent and concerning behavioral issue in dogs. Pit Bull dogs, known for their high levels of aggression, are recognized as a focus of concern in society. In our study, we aimed to investigate the behavioral characteristics of Pit Bull dogs and explore the potential roles of peptides involved in the neurobiology of aggression. Initially, female, and male dogs underwent aggression tests, and their aggression levels were categorized. Plasma nesfatin-1, serotonin, oxytocin, and dopamine levels were quantified using ELISA, with blood samples collected after a 24 h fasting period and 2 h post-refeeding. Our findings indicate that aggression in Pit Bull dogs correlates with decreased plasma nesfatin-1, serotonin, and oxytocin levels, while dopamine levels increase. The study's findings indicate that fasted dogs exhibited lower plasma levels of nesfatin-1, serotonin, and dopamine, while plasma oxytocin levels were higher. Furthermore, while the research findings do not suggest a significant relationship between the severity of aggression and the gender of the dog, male Pit Bull breeds appear to have higher plasma nesfatin-1 and serotonin levels compared to their female counterparts. The study's findings demonstrate that nesfatin-1, serotonin, oxytocin, and dopamine play pivotal roles in Pit Bull dogs' aggression, indicating potential interactions among these neuropeptides at the central nervous system level.

Central nervous system monoamine metabolite response to alcohol exposure is associated with future alcohol intake in a nonhuman primate model (Macaca mulatta)

It is widely held that the central monoamine neurotransmitters modulate alcohol intake. Few studies, however, directly assess the relationship between baseline and alcohol-induced monoamine turnover, as well as the change from baseline, as predictors of alcohol intake. Using a nonhuman primate model, this study investigates baseline, alcohol-induced and alcohol-induced change in monoamine activity and their relationship with alcohol intake. Alcohol-naïve, adolescent rhesus macaques (Macaca mulatta, N = 114) were administered a standardized intravenous bolus of alcohol solution (16.8%, v/v) on two occasions, approximately 1 month apart. One month prior to and 1 h following each alcohol infusion, cisternal cerebrospinal fluid (CSF) was obtained and assayed for monoamine metabolite concentrations. Approximately 6-7 months later, subjects were allowed unfettered access to an aspartame-sweetened alcohol solution (8.4%, v/v) for 1 h/day, 5 days/week, over 5-7 weeks. Results showed strong positive correlations between baseline and post-infusion CSF monoamine metabolite concentrations, indicating a trait-like response. Low baseline and post-infusion serotonin and dopamine metabolite concentrations and a smaller change in serotonin and dopamine metabolites from one infusion to the next were associated with higher alcohol intake. Low baseline and post-infusion norepinephrine metabolite concentrations predicted high alcohol intake, but unlike the other monoamines, a greater change in norepinephrine metabolite concentrations from one infusion to the next was associated with higher alcohol intake. These findings suggest that individual differences in naturally occurring and alcohol-induced monoamine activity, as well as the change between exposures, are important modulators of initial alcohol consumption and may play a role in the risk for excessive alcohol intake.

Inter-Individual Differences in Cognitive Tasks: Focusing on the Shaping of Decision-Making Strategies

In this paper, we review recent (published and novel) data showing inter-individual variation in decision-making strategies established by mice in a gambling task (MGT for Mouse Gambling Task). It may look intriguing, at first, that congenic animals develop divergent behaviors. However, using large groups of mice, we show that individualities emerge in the MGT, with about 30% of healthy mice displaying risk-averse choices while about 20-25% of mice make risk-prone choices. These strategies are accompanied by different brain network mobilization and individual levels of regional -prefrontal and striatal- monoamines. We further illustrate three ecological ways that influence drastically cognitive strategies in healthy adult mice: sleep deprivation, sucrose or artificial sweetener exposure, and regular exposure to stimulating environments. Questioning how to unmask individual strategies, what are their neural/neurochemical bases and whether we can shape or reshape them with different environmental manipulations is of great value, first to understand how the brain may build flexible decisions, and second to study behavioral plasticity, in healthy adult, as well as in developing brains. The latter may open new avenues for the identification of vulnerability traits to adverse events, before the emergence of mental pathologies.

Genetic association of nucleus accumbens 5-hydroxyindoleacetic acid level and alcohol preference drinking in a quasi-congenic male mice: Potential modulation by Grm7 gene polymorphism

OBJECTIVE

To test the hypothesis that predisposition to high alcohol drinking behavior is genetically associated with hypoactive serotonergic function in the Nucleus Accumbens (NAc).

METHOD

Alcohol avoiding C5A3 and alcohol preferring I5B25A mice of the Quasi-congenic Recombinant QTL Introgression (RQI) mouse strains were subjected to in vivo microdialysis in the NAc. Neurotransmitter and metabolite contents were analyzed by HPLC and samples were collected in three phases: Baseline, Control, and Alcohol. Samples were collected with 20 min intervals.

RESULTS

Between-strain differences restricted to small chromosome segments significantly affected both alcohol preference drinking and NAc 5-HIAA levels [F_{1, 13} = 5.569 p=.035 (General Linear Model Repeated Measures ANOVA and Tests of Between-Subjects Effects)]. Whole genome biallelic DNA marker genotyping allowed the identification of 16 differential microsatellite markers associated with low 5-HIAA levels and excessive alcohol drinking. Chromosome 6 markers were linked to Grm7 (51.19 centimorgan), a reported candidate gene for modulation of addiction. The results are consistent with earlier reports of association of low 5-HIAA and high alcohol consumption in rats and primates, including Homo sapiens.

CONCLUSION

Low NAc 5-HIAA and high alcohol consumption are genetically associated in a quasi-congenic mouse model carrying variants of the Grm7 gene. We propose that constitutional polymorphism in Grm7 may modulate CRF neuron activity via altered mGluR7 expression thus targeting CRF pathways to substance use circuits. This raises the possibility of modulation of DRN 5-HT neurons leading to hypo- or hyper-serotonergic condition in NAc and higher or lower alcohol preference drinking.

The behavioral neuroendocrinology of dopamine systems in differently reared juvenile male rhesus monkeys (Macaca mulatta)

Dopamine (DA) is a critical neuromodulator of behavior. With propensities for addiction, hyper-activity, cognitive impairment, aggression, and social subordinance, monkeys enduring early maternal deprivation evoke human disorders involving dopaminergic dysfunction. To examine whether DA system alterations shape the behavioral correlates of adverse rearing, male monkeys (Macaca mulatta) were either mother-reared (MR: N = 6), or separated from their mothers at birth and nursery-reared (NR: N = 6). Behavior was assessed during 20-minute observations of subjects interacting with same- or differently-reared peers. Cerebrospinal fluid (CSF) biogenic amines, and serum testosterone (T), cortisol (CORT), and prolactin (PRL) were collected before and after pharmacologic challenge with saline or the DA receptor-2 (DRD2) antagonist Raclopride (RAC). Neuropeptide correlations observed in MR were non-existent in NR monkeys. Compared to MR, NR showed reduced DA tone; higher basal serum T; and lower CSF serotonin (5-HT). RAC increased PRL, T and CORT, but the magnitude of responses varied as a function of rearing. Levels of PRL significantly increased following RAC in MR, but not NR. Elevations in T following RAC were only significant among MR. Contrastingly, the net change (RAC CORT - saline CORT) in CORT was greater in NR than MR. Finally, observations conducted during the juvenile phase in a novel play-arena revealed more aggressive, self-injurious, and repetitive behaviors, which negatively correlated with indexes of dopaminergic tone in NR monkeys. In conclusion, early maternal deprivation alters brain DA systems, and thus may be associated with characteristic cognitive, social, and addiction outcomes.

Early Rearing Conditions Affect Monoamine Metabolite Levels During Baseline and Periods of Social Separation Stress: A Non-human Primate Model (Macaca mulatta)

A variety of studies show that parental absence early in life leads to deleterious effects on the developing CNS. This is thought to be largely because evolutionary-dependent stimuli are necessary for the appropriate postnatal development of the young brain, an effect sometimes termed the "experience-expectant brain," with parents providing the necessary input for normative synaptic connections to develop and appropriate neuronal survival to occur. Principal among CNS systems affected by parental input are the monoamine systems. In the present study, N = 434 rhesus monkeys (233 males, 201 females) were reared in one of two conditions: as mother-reared controls (MR; n = 269) or without adults with 24-h access to same-aged peers (PR; n = 165). When subjects were six-months-old, they underwent a separation paradigm involving 4, sequential, four-day social separations from their mothers or peers, with each separation followed by three-day reunions with their mothers or their peers. Prior to the separation paradigm, baseline cisternal CSF samples were obtained, as well as at the end of each the four social separations, and after final separation, during a recovery period. CSF was assayed for concentrations of monoamine metabolites and a blood sample was genotyped for the serotonin transporter (5-HTT) genotype. Replicating earlier landmark findings, PR subjects with the s allele exhibited lower baseline concentrations of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA), when compared to PR subjects homozygous for the L allele. MR subjects were undifferentiated by genotype. PR subjects exhibited lower CSF 5-HIAA concentrations during baseline, but higher CSF 5-HIAA during social separations, when compared to MR subjects. There were rearing effects for the dopamine metabolite homovanillic acid (HVA) and for the norepinephrine metabolite 3-methoxy-4-hydroxyphenylglycol (MHPG), with PR subjects showing higher HVA and lower MHPG when compared to MR subjects. These findings indicate that there are long-term deficits in the response of monoamines following early maternal absence. The results of this study confirm and extend earlier findings that early parental absence has deleterious consequences for the development of the monoamine systems, and that these consequences are modulated by the 5-HTT genotype.

Neurological and neuropsychological effects of low and moderate prenatal alcohol exposure

Several explanations for the diverse results in research on foetal alcohol spectrum disorders or alcohol-related neurodevelopmental disorder might be at hand: timing, amount and patterns of alcohol exposure, as well as complex epigenetic responses. The genetic background of the offspring and its interaction with other prenatal and post-natal environmental cues are likely also of importance. In the present report, key findings about the possible effects of low and moderate doses of maternal alcohol intake on the neuropsychological development of the offspring are reviewed and plausible mechanisms discussed. Special focus is put on the serotonergic system within developmental and gene-environment frameworks. The review also suggests guidelines for future studies and also summarizes some of to-be-answered questions of relevance to clinical practice. Contradictory findings and paucity of studies on the effects of exposure to low alcohol levels during foetal life for the offspring's neuropsychological development call for large prospective studies, as well as for studies including neuroimaging and multi-omics analyses to dissect the neurobiological underpinnings of alcohol exposure-related phenotypes and to identify biomarkers. Finally, it remains to be investigated whether any safe threshold of alcohol drinking during pregnancy can be identified.

Abstinent Heroin Addicts Tend to Take Risks: ERP and Source Localization

Abnormal decision making is a behavioral characteristic of drug addiction. Indeed, drug addicts prefer immediate rewards at the expense of future interests. Assessing the neurocognitive basis of decision-making related to drug dependence, combining event-related potential (ERP) analysis and source localization techniques, may provide new insights into understanding decision-making deficits in drug addicts and further guide withdrawal treatment. In this study, EEG was performed in 20 abstinent heroin addicts (AHAs) and 20 age-, education- and gender-matched healthy controls (HCs) while they participated in a simple two-choice gambling task (99 vs. 9). Our behavioral results showed that AHAs tend to select higher-risk choices compared with HCs (i.e., more "99" choices than "9"). ERP results showed that right hemisphere preponderance of stimulus-preceding negativity was disrupted in AHAs, but not in HCs. Feedback-related negativity of difference wave was higher in AHAs than HCs, with the P300 amplitude associated with risk magnitude and valence. Using source localization that allows identification of abnormal brain activity in consequential cognitive stages, including the reward expectation and outcome evaluation stages, we found abnormalities in both behavioral and neural responses on gambling in AHAs. Taken together, our findings suggest AHAs have risk-prone tendency and dysfunction in adaptive decision making, since they continue to choose risky options even after accruing considerable negative scores, and fail to shift to a safer strategy to avoid risk. Such abnormal decision-making bias to risk and immediate reward seeking may be accompanied by abnormal reward expectation and evaluation in AHAs, which explains their high risk-seeking and impulsivity.

Social rank, chronic ethanol self-administration, and diurnal pituitary-adrenal activity in cynomolgus monkeys

RATIONALE

Dominance hierarchies affect ethanol self-administration, with greater intake among subordinate animals compared to dominant animals. Excessive ethanol intake disrupts circadian rhythms. Diurnal rhythms of the hypothalamic-pituitary-adrenal axis have not been characterized in the context of ethanol self-administration with regard to social rank.

OBJECTIVE

This study aimed to determine whether diurnal pituitary-adrenal hormonal rhythms account for differences between social ranks in ethanol self-administration or are differentially affected by ethanol self-administration between social ranks.

METHODS

During alternating individual (n = 11-12) and social (n = 3 groups) housing of male cynomolgus monkeys (Macaca fascicularis), diurnal measures of cortisol and adrenocorticotropic hormone (ACTH) were obtained from plasma samples three times per week. Social rank was determined, ethanol (4 %, w/v) self-administration was induced, and then the monkeys were allowed a choice of water or ethanol for 22 h/day for 49 weeks.

RESULTS

For all social ranks, plasma ACTH was elevated during social housing, but cortisol was stable, although greater among dominant monkeys. Ethanol self-administration blunted the effect of social housing, cortisol, and the diurnal rhythm for both hormones, regardless of daily ethanol intake (1.2-4.2 g/kg/day). Peak ACTH and cortisol were more likely to be observed in the morning during ethanol access. Ethanol, not vehicle, intake was lower during social housing across social ranks. Only dominant monkeys showed significantly lower blood-ethanol concentration during social housing.

CONCLUSIONS

There was a low threshold for disruption of diurnal pituitary rhythms by ethanol drinking, but sustained adrenal corticosteroid rhythms. Protection against heavy drinking among dominant monkeys may have constrained ethanol intoxication, possibly to preserve dominance rank.

Moderate prenatal alcohol exposure and serotonin genotype interact to alter CNS serotonin function in rhesus monkey offspring

BACKGROUND

Moderate prenatal alcohol exposure can contribute to neurodevelopmental impairments and disrupt several neurotransmitter systems. We examined the timing of moderate level alcohol exposure, serotonin transporter gene polymorphic region variation (rh5-HTTLPR), and levels of primary serotonin and dopamine (DA) metabolites in cerebrospinal fluid (CSF) in rhesus monkeys.

METHODS

Thirty-two 30-month old rhesus monkeys (Macaca mulatta) from 4 groups of females were assessed: (i) early alcohol-exposed group (n = 9), in which mothers voluntarily consumed 0.6 g/kg/d alcohol solution on gestational days 0 to 50; (ii) middle-to-late gestation alcohol-exposed group (n = 6), mothers consumed 0.6 g/kg/d alcohol solution on gestational days 50 to 135; (iii) a continuous-exposure group (n = 8), mothers consumed 0.6 g/kg/d alcohol solution on gestational days 0 to 135; and (iv) controls (n = 9), mothers consumed an isocaloric control solution on gestational days 0 to 50, 50 to 135, or 0 to 135. Serotonin transporter promoter region allelic variants (homozygous s/s or heterozygous s/l vs. homozygous l/l) were determined. We examined CSF concentrations of the 5-HT and DA metabolites, 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA), respectively, at baseline and 50 hours after separation from cage-mates, when the monkeys were 30 months old.

RESULTS

Early- and middle-to-late gestation-alcohol exposed monkeys carrying the short allele had lower concentrations of 5-HIAA in CSF relative to other groups. Concentrations of 5-HIAA in CSF were lower for s allele carriers and increased from baseline relative to pre-separation values, whereas 5-HIAA levels in l/l allele carriers were not affected by separation. Monkeys carrying the short allele had lower basal concentrations of HVA in CSF compared with monkeys homozygous for the long allele.

CONCLUSION

Carrying the s allele of the 5-HT transporter increased the probability of reduced 5-HIAA in early- and middle-to-late gestation alcohol-exposed monkeys and reduced HVA at baseline. These findings that prenatal alcohol exposure altered central 5-HT activity in genetically sensitive monkeys raise questions about whether abnormal serotonin biological pathways could underlie some of the psychiatric disorders reported in fetal alcohol spectrum disorder.

Neurobiological pathways linking socioeconomic position and health

Across individuals, risk for poor health varies inversely with socioeconomic position (SEP). The pathways by which SEP affects health have been viewed from many epidemiological perspectives. Central to these perspectives is the notion that socioeconomic health disparities arise from an interplay between nested, recursive, and cumulative environmental, social, familial, psychological, behavioral, and physiological processes that unfold over the life span. Epidemiological perspectives on socioeconomic health disparities, however, have not yet formally integrated emerging findings from neuropharmacological, molecular genetic, and neuroimaging studies demonstrating that indicators of SEP relate to patterns of brain neurotransmission, brain morphology, and brain functionality implicated in the etiology of chronic medical conditions and psychological disorders. Here, we survey these emerging findings and consider how future neurobiological studies in this area can enhance our understanding of the pathways by which different dimensions of SEP become embodied by the brain to influence health throughout life.

Platelet monoamine oxidase activity predicts alcohol sensitivity and voluntary alcohol intake in rhesus monkeys

Platelet monoamine oxidase B (MAO-B) has been proposed to be a biological marker for the properties of monoamine systems, with low activity being associated with vulnerability for high scores on personality traits such as sensation seeking, monotony avoidance, and impulsiveness, as well as for vulnerability for alcoholism. In the present study, platelet MAO-B activity was analysed in 78 rhesus macaques, and its relation to voluntary alcohol intake and behaviours after intravenous alcohol administration was observed. Monkeys with low platelet MAO-B activity had low levels of 5-hydroxyindole acetic acid in cerebrospinal fluid and showed excessive aggression after alcohol administration. A novel finding was that animals with low platelet MAO-B activity showed less intoxication following alcohol administration. As we have shown previously, they also voluntarily consumed more alcohol. We here replicate results from studies on both humans and non-human primates, showing the utility of platelet MAO as a marker for risk behaviours and alcohol abuse. Furthermore, we link platelet MAO activity to alcohol sensitivity.

Hybrid mice as genetic models of high alcohol consumption

We showed that F1 hybrid genotypes may provide a broader variety of ethanol drinking phenotypes than the inbred progenitor strains used to create the hybrids (Blednov et al. in Alcohol Clin Exp Res 29:1949-1958, 2005). To extend this work, we characterized alcohol consumption as well as intake of other tastants (saccharin, quinine and sodium chloride) in five inbred strains of mice (FVB, SJL, B6, BUB, NZB) and in their reciprocal F1 hybrids with B6 (FVBxB6; B6xFVB; NZBxB6; B6xNZB; BUBxB6; B6xBUB; SJLxB6; B6xSJL). We also compared ethanol intake in these mice for several concentrations before and after two periods of abstinence. F1 hybrid mice derived from the crosses of B6 and FVB and also B6 and SJL drank higher levels of ethanol than their progenitor strains, demonstrating overdominance for two-bottle choice drinking test. The B6 and NZB hybrid showed additivity in two-bottle choice drinking, whereas the hybrid of B6 and BUB demonstrated full or complete dominance. Genealogical origin, as well as non-alcohol taste preferences (sodium chloride), predicted ethanol consumption. Mice derived from the crosses of B6 and FVB showed high sustained alcohol preference and the B6 and NZB hybrids showed reduced alcohol preference after periods of abstinence. These new genetic models offer some advantages over inbred strains because they provide high, sustained, alcohol intake, and should allow mapping of loci important for the genetic architecture of these traits.

Tryptophan metabolism in alcoholism

Acute and chronic alcohol (ethanol) intake and subsequent withdrawal exert major effects on tryptophan (Trp) metabolism and disposition in human subjects and experimental animals. In rats, activity of the rate-limiting enzyme of Trp degradation, liver Trp pyrrolase (TP), is enhanced by acute, but inhibited after chronic, ethanol administration, then enhanced during withdrawal. These changes lead to alterations in brain serotonin synthesis and turnover mediated by corresponding changes in circulating Trp availability to the brain. A low brain-serotonin concentration characterizes the alcohol-preferring C57BL/6J mouse strain and many alcohol-preferring rat lines. In this mouse strain, liver TP enhancement causes the serotonin decrease. In man, acute ethanol intake inhibits brain serotonin synthesis by activating liver TP. This may explain alcohol-induced depression, aggression and loss of control in susceptible individuals. Chronic alcohol intake in dependent subjects may be associated with liver TP inhibition and a consequent enhancement of brain serotonin synthesis, whereas subsequent withdrawal may induce the opposite effects. The excitotoxic Trp metabolite quinolinate may play a role in the behavioural disturbances of the alcohol-withdrawal syndrome. Some abstinent alcoholics may have a central serotonin deficiency, which they correct by liver TP inhibition through drinking. Further studies of the Trp and serotonin metabolic status in long-term abstinence in general and in relation to personality characteristics, alcoholism typology and genetic factors in particular may yield important information which should facilitate the development of more effective screening, and preventative and therapeutic strategies in this area of mental health.

Novel strategies to mine alcoholism-related haplotypes and genes by combining existing knowledge framework

High-throughout single nucleotide polymorphism detection technology and the existing knowledge provide strong support for mining the disease-related haplotypes and genes. In this study, first, we apply four kinds of haplotype identification methods (Confidence Intervals, Four Gamete Tests, Solid Spine of LD and fusing method of haplotype block) into high-throughout SNP genotype data to identify blocks, then use cluster analysis to verify the effectiveness of the four methods, and select the alcoholism-related SNP haplotypes through risk analysis. Second, we establish a mapping from haplotypes to alcoholism-related genes. Third, we inquire NCBI SNP and gene databases to locate the blocks and identify the candidate genes. In the end, we make gene function annotation by KEGG, Biocarta, and GO database. We find 159 haplotype blocks, which relate to the alcoholism most possibly on chromosome 1 approximately 22, including 227 haplotypes, of which 102 SNP haplotypes may increase the risk of alcoholism. We get 121 alcoholism-related genes and verify their reliability by the functional annotation of biology. In a word, we not only can handle the SNP data easily, but also can locate the disease-related genes precisely by combining our novel strategies of mining alcoholism-related haplotypes and genes with existing knowledge framework.

Role of Serotonin and Dopamine System Interactions in the Neurobiology of Impulsive Aggression and its Comorbidity with other Clinical Disorders

Impulsive aggression is characterized by an inability to regulate affect as well as aggressive impulses, and is highly comorbid with other mental disorders including depression, suicidal behavior, and substance abuse. In an effort to elucidate the neurobiological underpinnings of impulsive aggression and to help account for its connections with these other disorders, this paper reviews relevant biochemical, brain imaging, and genetic studies. The review suggests that dysfunctional interactions between serotonin and dopamine systems in the prefrontal cortex may be an important mechanism underlying the link between impulsive aggression and its comorbid disorders. Specifically, serotonin hypofunction may represent a biochemical trait that predisposes individuals to impulsive aggression, with dopamine hyperfunction contributing in an additive fashion to the serotonergic deficit. The current paper proposes a modified diathesis-stress model of impulsive aggression in which the underlying biological diathesis may be deficient serotonergic function in the ventral prefrontal cortex. This underlying disposition can be manifested behaviorally as impulsive aggression towards oneself and others, and as depression under precipitating life stressors. Substance abuse associated with impulsive aggression is understood in the context of dopamine dysregulation resulting from serotonergic deficiency. Also discussed are future research directions in the neurobiology of impulsive aggression and its comorbid disorders.

Perception of sweet taste is important for voluntary alcohol consumption in mice

To directly evaluate the association between taste perception and alcohol intake, we used three different mutant mice, each lacking a gene expressed in taste buds and critical to taste transduction: alpha-gustducin (Gnat3), Tas1r3 or Trpm5. Null mutant mice lacking any of these three genes showed lower preference score for alcohol and consumed less alcohol in a two-bottle choice test, as compared with wild-type littermates. These null mice also showed lower preference score for saccharin solutions than did wild-type littermates. In contrast, avoidance of quinine solutions was less in Gnat3 or Trpm5 knockout mice than in wild-type mice, whereas Tas1r3 null mice were not different from wild type in their response to quinine solutions. There were no differences in null vs. wild-type mice in their consumption of sodium chloride solutions. To determine the cause for reduction of ethanol intake, we studied other ethanol-induced behaviors known to be related to alcohol consumption. There were no differences between null and wild-type mice in ethanol-induced loss of righting reflex, severity of acute ethanol withdrawal or conditioned place preference for ethanol. Weaker conditioned taste aversion (CTA) to alcohol in null mice may have been caused by weaker rewarding value of the conditioned stimulus (saccharin). When saccharin was replaced by sodium chloride, no differences in CTA to alcohol between knockout and wild-type mice were seen. Thus, deletion of any one of three different genes involved in detection of sweet taste leads to a substantial reduction of alcohol intake without any changes in pharmacological actions of ethanol.

Long-term citalopram maintenance in mice: selective reduction of alcohol-heightened aggression

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) alleviate many affective disturbances in human clinical populations and are used in animal models to study the influence of serotonin (5-HT) on aggressive behavior and impulsivity.

OBJECTIVE

We hypothesized that long-term SSRI treatment may reduce aggressive behavior escalated by alcohol consumption in mice. Therefore, aggression was tested in male CFW mice to determine whether repeated citalopram (CIT) administration reduces alcohol-heightened aggression.

MATERIALS AND METHODS

Resident male mice self-administered alcohol by performing an operant response on a panel placed in their home cage that delivered a 6% alcohol solution. Mice repeatedly confronted an intruder 15 min after self-administration of either 1 g/kg alcohol (EtOH) or water (H(2)O). Aggressive behaviors were higher in most mice when tests occurred after EtOH intake relative to H(2)O. Once baseline aggression was established, animals were injected (i.p.) twice daily with 10 mg/kg CIT or saline (SAL) for 32 days. Every 4 days throughout the CIT treatment period, aggressive encounters occurred 6 h after CIT injections, with testing conditions alternating between EtOH and H(2)O intake.

RESULTS

Aggression was only modestly affected by CIT in the first 2 weeks of treatment. However, by day 17 of CIT treatment, alcohol-heightened aggressive behavior was abolished, while baseline aggression remained stable. These data lend support for the role of the 5-HT transporter in the control of alcohol-related aggressive behavior, and the time course of effects suggests that a change in density of 5HT(1A) autoreceptors is necessary before antidepressant drugs produce beneficial outcomes.

Specific personality traits and dopamine, serotonin genes in anxiety-depressive alcoholism among Han Chinese in Taiwan

BACKGROUND

Cloninger [Cloninger CR. 1987. Neurogenetic adaptive mechanisms in alcoholism. Science 236: 410-416.] had proposed a psychobiological model suggesting that three main personality dimensions distinguish the alcoholism into two subtypes (type I and type II). However, the classification was equivocal for clinical diagnosis. Recently, anxiety-depressive alcohol dependence (ANX/DEP ALC) has been posited as a genetically specific subtype of alcoholism. Its clinical characteristics were similar to individuals with type I alcoholism [Cloninger, C.R. 1987. Neurogenetic adaptive mechanisms in alcoholism. Science 236: 410-6.] such as having a high comorbidity with mood disorder, late-onset and more anxious/depressed traits. We attempted to investigate whether the dopamine D2 receptor (DRD2) and the serotonin transporter promoter region (5-HTTLPR) genes were involved in Novelty Seeking (NS) and Harm Avoidance (HA) of ANX/DEP ALC.

METHODS

We recruited 46 pure alcohol dependents (Pure ALC) and 87 anxiety-depression alcohol dependents (ANX/DEP ALC). All participants were diagnosed by DSM-IV criteria, genotyped by the PCR method and assessed with Tridimensional Personality Questionnaire (TPQ).

RESULTS

Both NS and HA were high in ANX/DEP ALC (p = 0.021; p = 0.001, respectively). The association between NS and ANX/DEP ALC only existed in subjects with DRD2 TaqI A1(+) allele (A1/A1 or A1/A2 genotypes) (p = 0.004) and in those with S/S genotype of 5-HTTLPR (p = 0.005). With the stratification of DRD2 TaqI A1(+) allele, high NS of ANX/DEP ALC existed only in carriers of 5-HTTLPR S/S genotype (p=0.001). Moreover, ANX/DEP ALC was related to high HA only in samples carrying 5-HTTLPR S/L or L/L genotype (p = 0.02).

CONCLUSIONS

These findings provided the empirical genetic characterization of the specific personality traits in ANX/DEP ALC among Han Chinese population in Taiwan.

Increased accumbal dopamine during daily alcohol consumption and subsequent aggressive behavior in rats

BACKGROUND

Alcohol drinking may lead to increased aggression in certain individuals, and both fighting and drinking increase levels of dopamine and serotonin in mesocorticolimbic structures. Assessing the dynamic changes in these neurotransmitters during the course of drinking and fighting has remained challenging.

OBJECTIVE

The objective of the study was to learn about ongoing monoaminergic activity in the nucleus accumbens of rats that engaged in aggressive behavior after having consumed low doses of alcohol.

MATERIALS AND METHODS

After male members of breeding pairs of Long-Evans rats displayed reliable aggression toward an intruder into their home cage, they were trained to consume a 10% alcohol solution, leading to blood alcohol levels of 20-80 mg/dl. Subsequently, the effect of daily alcohol self-administration on aggression was determined in biweekly confrontations with an intruder. Finally, rats were implanted with a microdialysis probe aimed at the n. accumbens for sample collection before, during, and after a 10-min alcohol drinking session followed by a 10-min aggressive confrontation.

RESULTS

Accumbal dopamine, but not serotonin, levels tended to increase in anticipation of the daily alcohol session, reaching significance immediately after the alcohol session and remaining significantly elevated (by 40%) during and after the subsequent confrontation. No such changes were seen in residents that confronted an intruder without preceding alcohol consumption. Animals that had a history of becoming more aggressive after consumption of low levels of alcohol showed similar changes in dopamine levels as did animals that had no such history.

CONCLUSIONS

The rise in accumbal dopamine confirms previous findings and seems to reflect the anticipation of alcohol consumption; it persisted during the aggressive confrontation regardless of the level of aggression. The daily alcohol drinking for several months may have facilitated dopamine release and masked any further changes associated with the aggressive encounter.

Morphometry of dorsal raphe nucleus serotonergic neurons in alcoholism

BACKGROUND

Reduced serotonergic function is hypothesized in alcohol abuse and dependence. Serotonergic innervation of the cortex arises predominantly from the dorsal raphe nucleus (DRN). We sought to determine the number and morphometric characteristics of DRN serotonergic neurons postmortem in alcoholic individuals (n=9; age: 16-66 years; 8M:1F) compared with psychiatrically normal, nonalcoholic controls (n=6; age: 17-74 years; 4M:2F).

METHODS

Brainstems were collected at autopsy, fixed and cryoprotected. Alcohol dependence or abuse was determined by psychological autopsy (DSM-IV), the presence of liver fatty changes or cirrhosis and/or high blood alcohol level. Tissue was sectioned at 50 microm (-25 degrees C). A series of 1:10 sections was immunoreacted with antiserum to tryptophan hydroxylase (TPH), the rate-limiting enzyme in the biosynthesis of serotonin. The total number of TPH-immunoreactive (IR) DRN neurons was determined by stereology. Neuron morphometry indices were determined using a video-based imaging system attached to a microscope. We identified TPH-IR neurons every 1,000 microm in each brainstem and measured neuron area, total cross sectional neuron area, and the total area and density of immunolabeled processes.

RESULTS

Dorsal raphe nucleus neuron number (controls: 80,386+/-10,238; alcoholic individuals: 85,884+/-12,478) was not different between groups but TPH-IR was greater in alcoholic individuals throughout the rostrocaudal extent of the DRN. The volume of the DRN was 66+/-9 mm3 in controls and 55+/-5 mm3 in alcoholic individuals (p>0.05). The average size of DRN neurons did not differ between groups (353+/-12 microm2 for controls vs 360+/-15 microm2 for alcoholic subjects). However, the area occupied by neuron processes (area of processes/DRN area) was 2.2-fold greater in alcoholic individuals compared with controls (p<0.05).

CONCLUSIONS

The increased area occupied by neuron processes in alcoholic individuals may represent sprouting and, together with greater TPH-IR, be a compensatory response to impaired serotonergic transmission or cumulative effects of alcohol on the serotonin system.

Early adversity and alcohol availability persistently modify serotonin and hypothalamic–pituitary–adrenal-axis metabolism and related behavior: What experimental research on rodents and primates can tell us

Early experiences have profound influences on individual developmental trajectories. For example alcohol exposure during central nervous system development relates to a number of pathological consequences in adulthood. An increased risk of developing psychiatric disorders, like major depression and impulse-control-related pathologies is associated with alcohol exposure during fetal life and/or during adolescence. Additionally, adverse life experiences occurring early in development may exacerbate these consequences, while impinging on the same neural systems affected by precocious alcohol exposure. Conversely, a protective and/or stimulating environment may mitigate these alcohol-related negative outcomes. Experimental research in animal models constitutes a primary source of information in understanding both functional and dysfunctional human adaptations to these events. In this review, a selection of rodent and primate studies shows that developmental ethanol exposure on the one hand, and environmental treatments aimed at modifying the mother-offspring interaction on the other hand, independently modulate similar neuro-endocrine systems. In particular, we discuss the effects that the above-mentioned independent variables exert on the hypothalamic-pituitary-adrenal (HPA)-axis and on brain serotonergic pathways. Experimental evidence indicates that pathological adaptations of these systems are valuable predictors of human neuro-behavioral abnormalities like depression, impaired impulse control and alcohol abuse. Finally, a working hypothesis is proposed, which combines primate and rodent studies aimed: (i) at studying functional and pathological individual development following early ethanol consumption, and (ii) at heading towards a better definition of potential intervention strategies.

Puberty, hormones, and sex differences in alcohol abuse and dependence

Sex differences in patterns of drinking and rates of alcohol abuse and dependence begin to emerge during the transition from late puberty to young adulthood. Increases in pubertal hormones, including gonadal and stress hormones, are a prominent developmental feature of adolescence and could contribute to the progression of sex differences in alcohol drinking patterns during puberty. This paper reviews experimental and correlational studies of gonadal and stress-related hormone changes and their effects on alcohol drinking and other associated actions of alcohol. Mechanisms are suggested by which reproductive hormones and stress-related hormones may modulate neural circuits within the brain reward system to produce sex differences in alcohol drinking patterns and vulnerability to alcohol abuse and dependence which become apparent during the late pubertal period.

Genetic and Other Contributions to Alcohol Intake in Rhesus Macaques (Macaca mulatta)

BACKGROUND

The etiology of alcoholism and alcohol abuse, like many other complex diseases, is heterogeneous and multifactorial. Numerous studies demonstrate a genetic contribution to variation in the expression of alcohol-related disorders in humans. Over the past decade, nonhuman primates have emerged as a valuable model for some aspects of human alcohol abuse because of their phylogenetic proximity to humans. Long-term, longitudinal studies of rhesus macaques (Macaca mulatta) have provided much insight into environmental influences, especially early life experiences, on alcohol consumption and behavior patterns that characterize alcohol intake later in life. It is not known, however, whether there is a genetic component as well to the variation seen in alcohol consumption in rhesus macaques. A significant genetic component to variation in alcohol consumption in rhesus macaques would show for the first time that like humans, for nonhuman primates additive genetic influences are important. Moreover, their use as a model for alcohol-related disorders in humans would have even greater relevance and utility for designing experiments incorporating the expanding molecular genetics field, and allow researchers to investigate the interaction among the known environmental influences and various genotypes.

METHODS

In this study, we investigate factors contributing to variation in alcohol consumption of 156 rhesus macaques collected over 10 years when subjects were adolescent in age, belonging to a single extended pedigree, with each cohort receiving identical early rearing backgrounds and subsequent treatments. To measure alcohol consumption each animal was provided unfettered simultaneous access both to an aspartame-sweetened 8.4% (v/v) alcohol-water solution, the aspartame-sweetened vehicle, and to water for 1 hour each day during the early afternoon between 13:00 and 15:00 in their home cages for a period of 5 to 7 weeks. We use multiple regression to identify factors that significantly affect alcohol consumption among these animals and a maximum likelihood program (ASReml) that, controlling for the significant factors, estimates the genetic contribution to the variance in alcohol consumption.

RESULTS

Multiple regression analysis identified test cohort and rearing environment as contributing to 57 and 2%, respectively, of the total variance in alcohol consumption. Of the remaining 41% of the variance about half (19.8%) was attributable to additive genetic effects using a maximum likelihood program.

CONCLUSION

This study demonstrates that, as in humans, there are additive genetic factors that contribute to variation in alcohol consumption in rhesus macaques, with other nongenetic factors accounting for substantial portions of the variance in alcohol consumption, Our findings show the presence of an additive genetic component and suggest the potential utility of the nonhuman primate as a molecular genetics tool for understanding alcohol abuse and alcoholism.

Personality profile in type I alcoholism: long duration of alcohol intake and low serotonergic activity are predictive factors of anxiety proneness

The aim of the present study was to further investigate personality profiles in male type I alcohol-dependent subjects (n = 33), in relation to central serotonergic neurotransmission, history of excessive alcohol consumption and present use of tobacco. Central serotonergic neurotransmission was assessed by the prolactin (PRL) response to D-fenfluramine. By using the Temperament and Character Inventory and the Karolinska Scales of Personality, all subjects self-rated their personality profile. The results showed that individuals with low PRL response and long duration of excessive alcohol consumption had significantly higher anxiety proneness, and that years of excessive alcohol consumption was the strongest predictor. Long duration of excessive alcohol consumption thus appears to have an influence on personality traits in male type I alcohol-dependent individuals and these personality traits may therefore be a consequence of, rather than preceding, alcoholism in these individuals.

Role of Alcohol Consumption in Escalation to Violence

No other drug has been associated with aggressive and violent behavior more than alcohol has. A major characteristic of the link between alcohol and social interactions is the very large variation in who becomes more aggressive while drinking and who does not. Tracing the origins of these individual differences has led to a focus on predispositions, such as the antisocial behavior of Type 2 alcoholics. Successful development of an experimental procedure to model heightened aggressive behavior after voluntary consumption of alcohol has facilitated the neurobiologic analysis of the link between alcohol and aggression. From a pharmacologic perspective, consumption of low to moderate doses of alcohol engenders heightened aggressive behavior in a significant minority of individuals before the circulation of appreciable amounts of the aldehyde metabolite. Ionophoric receptors such as NMDA, 5-HT(3) and GABA(A) have been identified in the brain as major sites of action for alcohol in the dose range that is relevant for engendering heightened aggression. Actions at the GABA(A) receptor complex that depend on particular GABA(A) subunits appear to be necessary for alcohol-heightened aggression. Genes that encode the synthesis of these alpha and gamma subunits are potentially significant markers for those individuals that are prone to engage in heightened aggressive behavior after the consumption of alcohol. Of particular importance are the reciprocal interactions between GABA and serotonin. Activating specific serotonin receptor subtypes such as 5-HT(1B) receptors reduces alcohol-heightened aggressive behavior. How these GABAergic and serotonergic corticolimbic mechanisms for alcohol-heightened aggression develop during the adolescent period remains an area of urgent study.

Maternal aggression in Wistar rats: effect of 5-HT2A/2C receptor agonist and antagonist microinjected into the dorsal periaqueductal gray matter and medial septum

The objective of the present study was to assess the role of the 5-HT2A/2C receptor at two specific brain sites, i.e., the dorsal periaqueductal gray matter (DPAG) and the medial septal (MS) area, in maternal aggressive behavior after the microinjection of either a 5-HT2A/2C receptor agonist or antagonist. Female Wistar rats were microinjected on the 7th postpartum day with the selective agonist alpha-methyl-5-hydroxytryptamine maleate (5-HT2A/2C) or the antagonist 5-HT2A/2C, ketanserin. The agonist was injected into the DPAG at 0.2 (N = 9), 0.5 (N = 10), and 1.0 microg/0.2 microl (N = 9), and the antagonist was injected at 1.0 microg/0.2 microl (N = 9). The agonist was injected into the medial septal area (MS) at 0.2 (N = 9), 0.5 (N = 7), and 1.0 microg/0.2 microl (N = 6) and the antagonist was injected at 1.0 microg/0.2 microl (N = 5). For the control, saline was injected into the DPAG (N = 7) and the MS (N = 12). Both areas are related to aggressive behavior and contain a high density of 5-HT receptors. Non-aggressive behaviors such as horizontal locomotion (walking) and social investigation and aggressive behaviors such as lateral threat (aggressive posture), attacks (frontal and lateral), and biting the intruder were analyzed when a male intruder was placed into the female resident's cage. For each brain area studied, the frequency of the behaviors was compared among the various treatments by analysis of variance. The results showed a decrease in maternal aggressive behavior (number of bites directed at the intruder) after microinjection of the agonist at 0.2 and 1.0 microg/0.2 microl (1.6 +/- 0.7 and 0.9 +/- 0.3) into the DPAG compared to the saline group (5.5 +/- 1.1). There was no dose-response relationship with the agonist. The present findings suggest that the 5-HT2A/2C receptor agonist has an inhibitory effect on maternal aggressive behavior when microinjected into the DPAG and no effect when microinjected into the MS. Ketanserin (1.0 microg/0.2 microl) decreased locomotion when microinjected into the DPAG and MS, but did not affect aggressive behavior. We interpret these findings as evidence for a specific role of 5-HT2A/2C receptors in the DPAG in the inhibition of female aggressive behavior, dissociated from those on motor activity.

Risky decision making and the anterior cingulate cortex in abstinent drug abusers and nonusers

Risky decision making is a hallmark behavioral phenotype of drug abuse; thus, an understanding of its biological bases may inform efforts to develop therapies for addictive disorders. A neurocognitive task that measures this function (Rogers Decision-Making Task; RDMT) was paired with measures of regional cerebral perfusion to identify brain regions that may underlie deficits in risky decision making in drug abusers. Subjects were abstinent drug abusers (> or =3 months) and healthy controls who underwent positron emission tomography scans with H(2)(15)O. Drug abusers showed greater risk taking and heightened sensitivity to rewards than control subjects. Both drug abusers and controls exhibited significant activations in a widespread network of brain regions, primarily in the frontal cortex, previously implicated in decision-making tasks. The only significant group difference in brain activation, however, was found in the left pregenual anterior cingulate cortex, with drug abusers exhibiting less task-related activation than control subjects. There were no significant correlations between neural activity and task performance within the control group. In the drug abuse group, on the other hand, increased risky choices on the RDMT negatively correlated with activation in the right hippocampus, left anterior cingulate gyrus, left medial orbitofrontal cortex, and left parietal lobule, and positively correlated with activation in the right insula. Drug abuse severity was related positively to right medial orbitofrontal activity. Attenuated activation of the pregenual ACC in the drug abusers relative to the controls during performance on the RDMT may underlie the abusers' tendency to choose risky outcomes.

Neuroimaging of Rodent and Primate Models of Alcoholism: Initial Reports From the Integrative Neuroscience Initiative on Alcoholism

Neuroimaging of animal models of alcoholism offers a unique path for translational research to the human condition. Animal models permit manipulation of variables that are uncontrollable in clinical, human investigation. This symposium, which took place at the annual meeting of the Research Society on Alcoholism in Vancouver, British Columbia, Canada, on June 29th, 2004, presented initial findings based on neuroimaging studies from the two centers of the Integrative Neuroscience Initiative on Alcoholism funded by the National Institute on Alcohol Abuse and Alcoholism. Effects of alcohol exposure were assessed with in vitro glucose metabolic imaging of rat brain, in vitro receptor imaging of monkey brain, in vivo magnetic resonance imaging of monkey brain, and in vivo magnetic resonance spectroscopic quantification of alcohol metabolism kinetics in rat brain.

Personality traits in captive lion-tailed macaques (Macaca silenus)

Personality influences an individual's perception of a situation and orchestrates behavioral responses. It is an important factor in elucidating variation in behavior both within and between species. The major focus of this research was to test a method that differs from those used in most previous personality studies, while investigating the personality traits of 52 captive lion-tailed macaques from four zoos. In this study, data from behavioral observations, a P-type principal components analysis (PCA), and bootstrapped confidence intervals as criteria for judging the significance of factor loadings were used rather than subjective ratings, R-type factor analyses, and arbitrary rules of thumb to determine significance. We investigated the relationships among individual component scores and sex, hormonal status, and dominance rank (controlling for age and social group) using a multiple regression analysis with bootstrapped confidence intervals. Three personality dimensions emerged from this analysis: Component 1 contained Extraversion-like behaviors related to sociability and affiliativeness. The higher mean Component score for females suggests that they are more "extraverted" than males. Only agonistic behaviors were significantly related to component 2. High-ranking individuals exhibited higher mean Component 2 scores than mid- or low-ranked individuals. Bold and cautious behaviors both loaded positively on Component 3, suggesting a dimension related to curiosity. The mean Component 3 score for females was higher than the mean score for males. The method used in this study should facilitate intraspecific and general interspecific comparisons. Developing a standardized trait term list that is applicable to many species, and collecting trait term data in the same manner and concurrent with behavioral observations (and physiologic measures when feasible) could prove useful in primate research and should be explored.

Sweet liking, novelty seeking, and gender predict alcoholic status

BACKGROUND

The relationship between a hedonic response to sweet taste and a propensity to excessive alcohol drinking is supported by both animal and human studies. There is evidence indicating that the tendency to rate more concentrated sweet solutions as the most pleasurable (i.e., sweet liking) is associated with the genetic vulnerability to alcoholism. However, sweet liking by itself is insufficient to predict the alcoholic status of the individual. Our previous study indicated that alcoholic status can be predicted by a combination of hedonic response to sweet taste and personality profile as measured by the Tridimensional Personality Questionnaire (TPQ). This study was designed to further test this hypothesis.

METHODS

Participants were 165 patients admitted to a residential treatment program for the treatment of alcoholism, drug dependence and/or interpersonal problems secondary to substance-abusing family members. In addition to a routine medical examination, on the 24th day after admission, patients completed the TPQ, the standard sweet taste test was conducted, and paternal family history of alcoholism was evaluated.

RESULTS

Sweet liking was strongly associated with a paternal history of alcoholism. The odds of receiving an alcohol dependence diagnosis were shown to increase, on the average, by 11% for every one-point increase in the TPQ novelty-seeking score in sweet-liking but not in sweet-disliking subjects. Gender contributed independently to the probability of alcohol dependence, with males exhibiting higher rates of alcoholism than females.

CONCLUSIONS

These findings support the hypothesis that a hedonic response to sweet taste is associated with a genetic risk for alcoholism. Alcoholic status may be predicted by a combination of sweet liking, the TPQ novelty-seeking score, and gender in a mixed group of alcoholic, polysubstance-dependent, and psychiatric patients.

Controlled and behaviorally relevant levels of oral ethanol intake in rhesus macaques using a flavorant-fade procedure

BACKGROUND

Flavorant-fading procedures can initiate and maintain oral ethanol intake in rodents. The present study developed a similar procedure to achieve controlled and behaviorally relevant levels of ethanol intake in monkeys.

METHODS

Male rhesus macaques (N = 13) were initially given the opportunity to consume 0.5 g/kg of a 1% (w/v) ethanol plus 4% (w/v) Tang solution in 1-hr limited-access sessions without the requirement of an operant response. Once consumption was stable at a particular concentration (%) and/or amount (g/kg), animals were given access to higher concentrations and/or amounts of ethanol. Animals were tested on a bimanual motor skill (BMS) task 20 and 90 min after consumption to assess behavioral impairment. Blood alcohol levels (BALs) were assessed after a session in which animals had the opportunity to consume up to 3.0 g/kg of 6% (w/v) ethanol.

RESULTS

The gradual fading up of higher concentrations and amounts of ethanol resulted in controlled and robust levels (>2.0 g/kg) of ethanol intake in half of the subjects. Increasing the concentration of the sweetener from 4 to 6% (w/v) was effective in initiating consumption in three animals. Two monkeys required the additional step of presenting the increased-sweetener solutions after a meal (postprandial consumption) to initiate significant ethanol intake. Animals were significantly impaired on the BMS task after consumption of 2.0, 2.5, and 3.0 g/kg of ethanol. Individual consumption ranging from 0.8 to 3.0 g/kg of ethanol produced BALs of 18 to 269 mg/dl.

CONCLUSIONS

The flavorant-fading procedure was effective in producing behaviorally relevant levels of ethanol consumption in rhesus macaques. This model facilitated a randomized-dose procedure to determine the behavioral effects of 0.5 to 3.0 g/kg of ethanol. This procedure therefore is of significant utility in determining behavioral or physiologic effects of specific doses of consumed ethanol in monkeys.

What are the costs of marital conflict and dissolution to children's physical health?

Do parental marital conflict and dissolution influence the risk trajectory of children's physical health risk? This paper reviews evidence addressing this question in the context of understanding how early environmental adversities may trigger a succession of risks that lead to poor health in childhood and greater risk for chronic health problems in adulthood. We first review existing evidence linking marital conflict and dissolution to offspring's physical health outcomes. Next, we provide evidence supporting biopsychosocial pathways that may link marital conflict and dissolution with accelerated health risk trajectories across the lifespan. Specifically, we posit that consequential to the stresses associated with marital conflict and disruption, parenting practices are compromised, leading to offspring deficits in affective, behavioral, and cognitive domains. These deficits, in turn, are hypothesized to increase health risk through poor health behaviors and by altering physiological stress-response systems, including neuroendocrine, cardiovascular, and neurotransmitter functioning. On the basis of the available direct evidence and theoretically plausible pathways, it appears that there is a cost of marital conflict and disruption to children's health; however, more comprehensive investigations are needed to further elucidate this relationship. In the final section, we address limitations in the current literature and identify research that is needed to better evaluate the association between marital conflict and dissolution and children's physical health.

Physiological predictors of reproductive outcome and mother-infant behaviors in captive rhesus macaque females (Macaca mulatta)

Previous research has shown that offspring of females with low cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA) concentrations are less likely to survive the first year of life than are offspring of females with high CSF 5-HIAA concentrations. In addition, studies of free-ranging rhesus macaque males have suggested that individuals with low CSF 5-HIAA concentrations suffer reduced reproductive success relative to their high serotonin counterparts. We examined CSF concentrations of the monoamine metabolites 5-HIAA and homovanillic acid (HVA), and plasma cortisol concentrations as predictors of first-time adult reproductive potential, maternal behavior, and overall social interactions in two groups of captive female rhesus macaques and their first offspring. Repeated CSF and blood samples were obtained from adult females in two social groups, and focal observations were performed for both new mothers and infants during the first month following parturition. We found that the reproductively aged nulliparous females who failed to give birth to their first offspring showed significantly lower CSF 5-HIAA concentrations than those females who gave birth. Among those females that gave birth to offspring, females with low CSF 5-HIAA concentrations and females with high plasma cortisol concentrations were overly protective and restrictive with their infants. CSF HVA concentration was not associated with reproductive output, social behavior, aggression, or mother-infant interactions in this sample of rhesus macaque females. We conclude that low CNS serotonin activity and high stress, measured by high plasma cortisol, are correlated with reduced reproductive success and patterns of high maternal restrictiveness in young adult female rhesus macaques.

Phasic alterations in dopamine and serotonin release in striatum and prefrontal cortex in response to cocaine predictive cues in behaving rhesus macaques

The ability of environmental cues associated with cocaine availability to cause relapse may result from conditioned activation of dopamine (DA) release. We examined this hypothesis in macaque monkeys by conducting microdialysis studies in animals during exposure to a cocaine predictive compound cue. In addition to studying DA release in mesolimbic and sensorimotor striatum, both DA and serotonin levels were determined in the prefrontal cortex (medial orbitofrontal and anterior cingulate). The compound cue employed visual, auditory, and olfactory components, and was salient to the animals as demonstrated by anticipatory lever pressing in the absence of cocaine. During a 10-min period of exposure prior to cocaine availability, there was no significant increase in striatal or cortical DA. The addition of a DA uptake inhibitor to the striatal perfusate to reduce the potential interference of neuronal uptake did not alter the results. In contrast to the lack of any change in striatal DA, a significant decrease in extracellular serotonin in the prefrontal cortex during the 10 min of cue exposure was observed.

Maternal separation alters maternal care, but has minor effects on behavior and brain opioid peptides in adult offspring

The aim of the study was to investigate the effect of repeated maternal separation (MS; 4 hr per day) during postnatal Days 1 to 15 on emotionality and voluntary ethanol intake in adult male and female Wistar rat offspring relative to controls exposed to a brief (5-min) daily handling procedure. Brain immunoreactive opioid peptide levels and plasma levels of corticosterone also were measured. There were mainly no alterations in any of the tested behaviors (i.e., fleeing and freezing responses, exploratory behavior, spontaneous and amphetamine-induced locomotor activity and competitive behavior), ethanol intake, or immunoreactive opioid peptide levels in MS offspring, either in males or females, compared to their respective controls nor were there any differences in plasma corticosterone between groups. In addition, the dams' retrieval behavior of the pups also was studied, showing that MS dams spent more time in the nest with the pups after the 4-hr separation period compared to control dams. With respect to the used protocol of the MS procedure in the present study, our results do not provide support for the suggestion that this procedure is a relevant model for studying development of psychopathology and vulnerability to drug abuse.

Advances in nonhuman primate alcohol abuse and alcoholism research

Advances in our understanding of the biological basis of alcohol abuse and alcoholism and the development of prevention and therapeutic intervention require appropriate animal models. Nonhuman primates are important to the study of complex biomedical disease processes. Genetic, anatomical, physiological, and behavioral similarities to humans offer unique opportunities for translational research along with the advantage of a degree of experimental control that is not possible in human studies. The purpose of this review is to outline the approaches taken with nonhuman primates as subjects in alcohol research and to highlight our current understanding of data on organismal variables that can be uniquely studied in these complex organisms. We review literature on alcohol self-administration to provide an integrative framework for discussion of progress in 2 important areas of research. Designs that incorporate self-administration provide a context for studying excessive alcohol consumption, including the organismal and environmental factors that influence risk for heavy drinking. We then review the use of monkeys to identify aspects of adverse biomedical consequences that follow excessive alcohol consumption. One of the primary conclusions to be drawn from this review is that nonhuman primates are a central part of the translational bridge in alcohol research, providing powerful and unique opportunities for experimental work that can address the biomedical complexities of alcohol abuse and alcoholism.

Family History of Alcoholism and Response to Sweets

BACKGROUND

The relationship between a hedonic response to sweet tastes and a propensity to excessive alcohol drinking is supported by both animal and human studies. This study was designed to test the hypothesis that the genetic risk for alcoholism as measured by a paternal history of alcoholism in young social drinkers is associated with sweet-liking, defined as rating the strongest offered sucrose solution (i.e., 0.83 M) as the most palatable during the standard sweet test.

METHODS

Participants were 163 subjects (39% male) without a lifetime history of alcohol or drug abuse or dependence. Eighty-one subjects had a paternal history of alcoholism (FH+), and 82 did not (FH-). Each subject rated a series of sucrose solutions for intensity of sweetness and palatability. Subjects were categorized as sweet-likers if they rated the highest sucrose concentration as the most pleasurable.

RESULTS

The estimated odds of being a sweet-liker were 2.5 times higher for FH+ than for FH- subjects. FH+ subjects disliked the tastes of the two weakest offered sucrose concentrations (0.05 and 0.10 M), whereas FH- subjects reported these tastes to be neutral.

CONCLUSIONS

The results of this study support the hypothesis that sweet-liking is associated with a genetic vulnerability to alcoholism.

Manipulations during the second, but not the first, week of life increase susceptibility to cocaine self-administration in female rats

We compared the effects of manipulations during week 1 vs week 2 of life on the propensity to self-administer cocaine. Pups received daily subcutaneous saline injections, were handled briefly, or remained undisturbed during their respective treatment periods. Animals handled during the second week of life exhibited increased locomotor response to novelty when tested on postnatal day (PND) 48, compared to all other groups. Rats were implanted with jugular catheters on PND 70 and then given the opportunity to self-administer (0.125 mg/kg/infusion) cocaine for 5 consecutive days (1 h sessions). The dose was then raised to 0.25 mg/kg/infusion for 5 days and to 0.5 mg/kg/infusion for the final 5 days of testing. Only animals manipulated during the second week of life acquired drug-taking behavior. These effects were both stimulus- and gender-specific. Females handled during the second week of life acquired cocaine self-administration (SA) at the lowest dose, and females injected during the second week of life acquired at the intermediate dose. Males injected during the second week of life showed a similar, but more variable, drug-taking pattern. There were no group differences in serum corticosterone response to novelty, although relative to undisturbed animals and those manipulated in the first week of life, female animals manipulated during the second week of life had lower basal expression of hippocampal glucocorticoid receptor mRNA in adulthood. We conclude that the second week of life in the rodent is a sensitive period during which manipulations result in a more vulnerable phenotype for the acquisition of cocaine SA.

Tobacco use is associated with reduced central serotonergic neurotransmission in type 1 alcohol-dependent individuals

BACKGROUND

Reduced central serotonergic neurotransmission in alcohol dependence may be attributed to the effects of cigarette smoking (and possibly more specifically to nicotine) rather than to alcoholism or its subtypes. The aim of the present study was therefore to compare central serotonergic neurotransmission in tobacco-using (cigarette smokers and users of smokeless tobacco, i.e., snuffers) alcohol-dependent individuals to that of tobacco-nonusing alcohol-dependent individuals.

METHODS

The central serotonergic neurotransmission was assessed by the prolactin (PRL) response to the serotonin-releasing agent D-fenfluramine (30 mg orally). Male subjects (n = 37) aged 20-65 years were recruited for this purpose. They were all type 1 alcohol-dependent individuals and had ended their alcohol intake the day before the D-fenfluramine challenge test.

RESULTS

There was no difference in baseline PRL concentrations between tobacco-using (n = 18) and tobacco-nonusing (n = 19) alcohol-dependent individuals. On the other hand, the maximum PRL response after D-fenfluramine was significantly lower in the tobacco-using group as compared to the tobacco-nonusing individuals.

CONCLUSION

Whether the reduction in central serotonergic neurotransmission in tobacco-using alcohol-dependent individuals is pre-existing or a result of tobacco use remains to be elucidated.

Alcohol and violence and the possible role of serotonin

BACKGROUND

There is undisputed evidence linking alcohol consumption and violence and other forms of aggressive behaviour, and also linking aggression with dysfunction of the brain indolylamine serotonin (5-hydroxytryptamine or 5-HT). Alcohol consumption also causes major disturbances in the metabolism of brain serotonin. In particular, acute alcohol intake depletes brain serotonin levels in normal (non-alcohol-dependent) subjects. On the basis of the above statements, it is suggested that, at the biological level, alcohol may induce aggressive behaviour in susceptible individuals, at least in part, by inducing a strong depletion of brain serotonin levels.

AIMS

In this article, evidence supporting these interrelationships and interactions will be summarized and discussed, the alcohol serotonin aggression hypothesis will be reiterated, and potential intervention strategies will be proposed.

Adverse childhood experiences and personal alcohol abuse as an adult

Adult alcohol abuse has been linked to childhood abuse and family dysfunction. However, little information is available about the contribution of multiple adverse childhood experiences (ACEs) in combination with parental alcohol abuse, to the risk of later alcohol abuse. A questionnaire about childhood abuse, parental alcoholism and family dysfunction while growing up was completed by adult HMO members in order to retrospectively assess the independent relationship of eight ACEs to the risk of adult alcohol abuse. The number of ACEs was used in stratified logistic regression models to assess their impact on several adult alcohol problems in the presence or absence of parental alcoholism. Each of the eight individual ACEs was associated with a higher risk alcohol abuse as an adult. Compared to persons with no ACEs, the risk of heavy drinking, self-reported alcoholism, and marrying an alcoholic were increased twofold to fourfold by the presence of multiple ACEs, regardless of parental alcoholism. Prevention of ACEs and treatment of persons affected by them may reduce the occurrence of adult alcohol problems.

Serotonin-transporter polymorphism pharmacogenetics in diarrhea-predominant irritable bowel syndrome

BACKGROUND & AIMS

A serotonin (5-HT)(3) receptor antagonist relieves symptoms in women with diarrhea-predominant irritable bowel syndrome (D-IBS). 5-HT undergoes reuptake by a transporter protein (SERT). Polymorphisms in the promoter for synthesis of SERT (SERT-P) influence response to serotonergic medications in depression. Our hypothesis is that polymorphisms of the promoter region for the SERT influence colonic transit in response to treatment with alosetron in D-IBS.

METHODS

Thirty patients (15 men, 15 women) with D-IBS received 1 mg twice a day alosetron for 6 weeks; colonic transit was measured by scintigraphy at baseline and at the end of treatment. Twenty-three patients consented to provide blood DNA samples. Long, short, and heterozygous SERT polymorphisms were identified by polymerase chain reaction-based restriction fragment length polymorphisms and confirmed by direct sequencing. We sought pharmacogenomic association of long, short, and heterozygote polymorphisms with a change in colonic transit and with an a priori-defined, clinically meaningful change in transit at 24 hours (>1.1 colonic regions).

RESULTS

SERT polymorphisms tended to be associated with colonic transit response (P = 0.075); there was a greater response in those with long homozygous than heterozygous polymorphisms (P = 0.039). Slowing of transit by >1.1 colonic region was observed in 9 women and 3 men and was more frequent in long homozygous than heterozygous patients (P = 0.024). Age, gender, and duration of IBS were not significantly different in the 3 groups.

CONCLUSIONS

Genetic polymorphisms at the SERT promoter influence response to a 5-HT(3) antagonist in D-IBS and may influence benefit-risk ratio with this class of compounds.