Adrenal steroid hormones and ethanol self-administration in male rhesus macaques

Long-term drinking stability in the open-access self-administration monkey model

The Non-Human Primate (NHP) model for the study of Alcohol Use Disorders (AUD) as developed in our laboratories is critical to our understanding of the pathophysiology of voluntary, chronic, ethanol consumption. Previous work in this model established categories of ethanol consumption that parallel reported categories of human consumption across a spectrum spanning low drinking, binge drinking, heavy drinking, and very heavy drinking, albeit at generally higher daily intakes across categories than documented in people. Original categories assigned to ethanol consumption patterns were established using a limited cohort of rhesus macaques. This study revisits the validity of categorical drinking using an additional 28 monkeys. In addition to finding categorical representations consistent with the original 2014 report, our findings demonstrate that drinking categories remain stable across the observed 12 months of nearly consistent access to ethanol (22 h/day), termed "open access". Animals occupying the two ends of the spectrum, "low" and "very heavy" drinkers, exhibit the largest stability. The findings also indicate a slight escalatory drift over time, with very heavy drinking animals experiencing fatigue near the end of open access.

Role of aldosterone and mineralocorticoid receptor (MR) in addiction: A scoping review

Preclinical and human studies suggest a role of aldosterone and mineralocorticoid receptor (MR) in addiction. This scoping review aimed to summarize (1) the relationship between alcohol and other substance use disorders (ASUDs) and dysfunctions of the aldosterone and MR, and (2) how pharmacological manipulations of MR may affect ASUD-related outcomes. Our search in four databases (MEDLINE, Embase, Web of Science, and Cochrane Library) indicated that most studies focused on the relationship between aldosterone, MR, and alcohol (n = 30), with the rest focused on opioids (n = 5), nicotine (n = 9), and other addictive substances (n = 9). Despite some inconsistencies, the overall results suggest peripheral and central dysregulations of aldosterone and MR in several species and that these dysregulations depended on the pattern of drug exposure and genetic factors. We conclude that MR antagonism may be a promising target in ASUD, yet future studies are warranted.

[Indicators of spontaneous behavior of rhesus monkeys with short-term course alcohol self-administration under free choice]

OBJECTIVE

To analyze spontaneous behavior in 36 male rhesus macaques during formation of alcoholic motivation under free choice.

MATERIAL AND METHODS

The model composed the initiation stage with the provision of an aqueous ethanol solution of increasing concentration from 1 to 4% with a sweetener and restricted access to the tap water supply and the subsequent stage of the formation of alcoholic motivation with a free choice between 4% ethanol solution without sweetener and water. The behavior was recorded by the «One-Zero» method with ethogram compiled in accordance with the behavioral peculiarities of rhesus monkeys when housed individually. Three subgroups of high, medium and low-level ethanol consumption were distinguished.

RESULTS

In the subgroup of high ethanol consumption median consumption was 1.70 g/kg/day at initiation (p<0.05, compared to other subgroups) and 1.79 g/kg/day (p<0.05) at free choice stage. Animals of high consumption subgroup had significantly higher frequency being at the cage bottom and in a sitting posture. We observed significant changes in a number of indicators of spontaneous behavior depending on the level of ethanol consumption, which included displacement behavior, stereotypic behavior and posture of animals. In the high consumption subgroup, there was a significant increase in the frequency of stereotypic behavior, atypical behavior, being on four legs, as well as a decrease in the frequency of being at the back side of the cage and of displacement behavior. At the same time, the inhibitory effect of ethanol on the hypothalamic-pituitary-adrenal system was revealed.

CONCLUSION

In the model of free choice alcohol self-administration rhesus monkeys demonstrate a significant change in a number of indicators of spontaneous behavior depending on the level of ethanol consumption, which includes displacement, stereotypic behaviors and animal posture.

Pairing food and drink: A physiological model of blood ethanol levels for a variety of drinking behaviors

We present a blood ethanol concentration compartment model which utilizes an animal's ethanol intake, food intake, and weight to predict the animal's blood ethanol concentration at any given time. By incorporating the food digestion process into the model we can predict blood ethanol concentration levels over time for a variety of drinking and eating scenarios. The model is calibrated and validated using data from cohorts of male monkeys, and is able to capture blood ethanol concentration kinetics of the monkeys from a variety of drinking behavior classifications.

Replicability in measures of attentional set-shifting task performance predicting chronic heavy drinking in rhesus monkeys

This study was designed to replicate and extend a previous report that the increase in performance of an attentional set-shifting task (ASST) in rhesus monkeys predicted their future alcohol drinking status as a heavy drinker (HD) or non-heavy drinker (NHD). A cohort of 6 young adult male monkeys was trained and tested under the same ASST and then underwent a alcohol self-administration protocol that maintained open-access (22 hours/day) choice of alcohol or water 7 days/week for approximately 6 months. The average improvement in performance in the ASST, as measured by a performance index, was replicated in the cohort of 6 monkeys when compared to the increase in the task performance in a previous cohort of 9 male monkeys. The alcohol self-administration protocol was then used to determine the drinking status (HD: n = 4 or NHD: n = 2) of the replicate cohort, which was accurately predicted by the performance on the ASST. Finally, individuals from both cohorts could be combined based on future drinking status of HD (n = 8) or NHD (n = 7), and the association with pre-alcohol ASST performance remained. Specifically, monkeys that had lower rates of PI improvement were more likely to become HDs. To our knowledge, this is the first study to replicate that deficits in the set-shifting performance can predict chronic heavy alcohol drinking in primates.

Discriminative Stimulus Effects and Metabolism of Ethanol in Rhesus Monkeys

BACKGROUND

Animal models are an essential feature of drug and pharmacotherapy development for treating alcohol use disorders (AUDs). The rhesus macaque is a robust animal model for many aspects of AUDs particularly in exploiting individual differences in oral self-administration of ethanol (EtOH), endocrine orchestration of stress response, and menstrual cycle characteristics. However, the clearance rates of EtOH have not been reported in this species, and the GABAA and N-methyl-D-aspartate (NMDA) receptor involvement in EtOH's discriminative stimulus effects has not been fully characterized.

METHODS

EtOH clearance rates following 2 doses of EtOH on separate days (0.5 and 1.0 g/kg, i.g.) were determined in 8 young adult male rhesus macaques. The EtOH was given by nasogastric gavage, and repeated blood samples were taken over 5 hours without sedation. Next, all subjects were trained on a 2-choice 1.0 g/kg EtOH (i.g.) versus water discrimination with a 60-minutes pretreatment period to capture peak blood EtOH concentration (BEC). Substitution testing was conducted with GABAA ligands pentobarbital (i.g. and i.m.) and midazolam (i.g.), as well as NMDA antagonist MK-801 (i.m.).

RESULTS

Peak BECs were 34 and 87 mg/dl for 0.5 and 1.0 g/kg doses, respectively, and occurred at 66 and 87 minutes following gavage. All GABAA and NMDA ligands tested resulted in responding on the EtOH-appropriate lever with the potency ranking of MK-801 (ED50 : 0.017 mg/kg) > midazolam (ED50 : 1.6 mg/kg) > pentobarbital (ED50 : 3.7 mg/kg) > EtOH (ED50 : 700 mg/kg, or 0.7 g/kg) in these subjects.

CONCLUSIONS

These results suggest that the compound discriminative stimulus effects of EtOH are highly consistent across species, providing further support for the rhesus macaque as strong model for pharmacotherapy development for AUD.

Cross-Species Co-analysis of Prefrontal Cortex Chronic Ethanol Transcriptome Responses in Mice and Monkeys

Despite recent extensive genomic and genetic studies on behavioral responses to ethanol, relatively few new therapeutic targets for the treatment of alcohol use disorder have been validated. Here, we describe a cross-species genomic approach focused on identifying gene networks associated with chronic ethanol consumption. To identify brain mechanisms underlying a chronic ethanol consumption phenotype highly relevant to human alcohol use disorder, and to elucidate potential future therapeutic targets, we conducted a genomic study in a non-human primate model of chronic open-access ethanol consumption. Microarray analysis of RNA expression in anterior cingulate and subgenual cortices from rhesus macaques was performed across multiple cohorts of animals. Gene networks correlating with ethanol consumption or showing enrichment for ethanol-regulated genes were identified, as were major ethanol-related hub genes within these networks. A subsequent consensus module analysis was used to co-analyze monkey data with expression data from a chronic intermittent ethanol vapor-exposure and consumption model in C57BL/6J mice. Ethanol-related gene networks conserved between primates and rodents were enriched for genes involved in discrete biological functions, including; myelination, synaptic transmission, chromatin modification, Golgi apparatus function, translation, cellular respiration, and RNA processing. The myelin-related network, in particular, showed strong correlations with ethanol consumption behavior and displayed marked network reorganization between control and ethanol-drinking animals. Further bioinformatics analysis revealed that these networks also showed highly significant overlap with other ethanol-regulated gene sets. Altogether, these studies provide robust primate and rodent cross-species validation of gene networks associated with chronic ethanol consumption. Our results also suggest potential novel focal points for future therapeutic interventions in alcohol use disorder.

Time for a Drink? A Mathematical Model of Non-human Primate Alcohol Consumption

We simulate a non-human primate's alcohol drinking pattern in order to better understand temporal patterning of alcoholic drinks that can lead to the excessive intakes associated with alcohol use disorder. A stochastic mathematical model of alcohol consumption pattern is developed, where model parameters are calibrated to an individual monkey's drinking history. The model predicts a time series that simulates a monkey's alcohol intake in time, and we analyze this drinking pattern to understand the variations in day and night drinking, the lengths of drinks (intake in 5 or more consecutive secs), and lengths of bouts (1 or more drinks per 5 min occasion). This time series can predict a lifetime categorical drinking level (light, binge, heavy, or very heavy), thus correlating an individual monkey's parameters with distinct long term drinking classifications.

Low cognitive flexibility as a risk for heavy alcohol drinking in non-human primates

Chronic alcohol abuse is frequently considered a habitual or inflexible behavior; however, measures of pre-existing cognitive flexibility prior to initiation of alcohol use are usually not available. This study used rhesus monkeys and an attentional set-shifting task to investigate whether pre-existing cognitive flexibility would predict increased risk for heavy alcohol drinking. As previously reported, monkeys were given 30 daily set-shifting sessions prior to alcohol access. These sessions consisted of the same sequence of eight unique visual discriminations (sets) of two objects that varied on two dimensions (shapes and colors). The ratio of errors per trials, session duration, and maximum set reached were primary dependent variables from each session and were used to compose a session performance index (PI) that ranged from a low performance PI of 31 to an optimal performance PI of 247. Here, animals underwent an alcohol induction period followed by 22 weeks of daily (22-h) self-administration sessions with free access to water and alcohol. Based on average daily alcohol intake during 22 weeks of 22-h/day access, the monkeys were categorized as non-heavy (mean = 2.0 ± 0.3 g/kg/day; n = 3) and heavy (mean = 3.3 ± 0.5 g/kg/day; n = 6) drinkers. The two groups diverged in performance on the set-shifting task across the 30 pre-alcohol sessions, and at the end of the pre-alcohol testing, the group average PI was 216 ± 27 and 137 ± 71 for the future non-heavy and heavy drinkers, respectively. The data show that low cognitive flexibility assessed with a set-shifting procedure was predictive of future classification as a heavy alcohol drinker. The data highlight individual differences in both cognitive flexibility and in alcohol self-administration in this population of rhesus monkeys.

A relationship between the aldosterone-mineralocorticoid receptor pathway and alcohol drinking: preliminary translational findings across rats, monkeys and humans

Aldosterone regulates electrolyte and fluid homeostasis through binding to the mineralocorticoid receptors (MRs). Previous work provides evidence for a role of aldosterone in alcohol use disorders (AUDs). We tested the hypothesis that high functional activity of the mineralocorticoid endocrine pathway contributes to vulnerability for AUDs. In Study 1, we investigated the relationship between plasma aldosterone levels, ethanol self-administration and the expression of CYP11B2 and MR (NR3C2) genes in the prefrontal cortex area (PFC) and central nucleus of the amygdala (CeA) in monkeys. Aldosterone significantly increased after 6- and 12-month ethanol self-administration. NR3C2 expression in the CeA was negatively correlated to average ethanol intake during the 12 months. In Study 2, we measured Nr3c2 mRNA levels in the PFC and CeA of dependent and nondependent rats and the correlates with ethanol drinking during acute withdrawal. Low Nr3c2 expression levels in the CeA were significantly associated with increased anxiety-like behavior and compulsive-like drinking in dependent rats. In Study 3, the relationship between plasma aldosterone levels, alcohol drinking and craving was investigated in alcohol-dependent patients. Non-abstinent patients had significantly higher aldosterone levels than abstinent patients. Aldosterone levels positively correlated with the number of drinks consumed, craving and anxiety scores. These findings support a relationship between ethanol drinking and the aldosterone/MR pathway in three different species.

Synaptic adaptations to chronic ethanol intake in male rhesus monkey dorsal striatum depend on age of drinking onset

One in 12 adults suffer with alcohol use disorder (AUD). Studies suggest the younger the age in which alcohol consumption begins the higher the probability of being diagnosed with AUD. Binge/excessive alcohol drinking involves a transition from flexible to inflexible behavior likely involving the dorsal striatum (caudate and putamen nuclei). A major focus of this study was to examine the effect of age of drinking onset on subsequent chronic, voluntary ethanol intake and dorsal striatal circuitry. Data from rhesus monkeys (n = 45) that started drinking as adolescents, young adults or mature adults confirms an age-related risk for heavy drinking. Striatal neuroadaptations were examined using whole-cell patch clamp electrophysiology to record AMPA receptor-mediated miniature excitatory postsynaptic currents (mEPSCs) and GABAA receptor-mediated miniature inhibitory postsynaptic currents (mIPSCs) from medium-sized spiny projection neurons located in the caudate or putamen nuclei. In controls, greater GABAergic transmission (mIPSC frequency and amplitude) was observed in the putamen compared to the caudate. With advancing age, in the absence of ethanol, an increase in mIPSC frequency concomitant with changes in mIPSC amplitude was observed in both regions. Chronic ethanol drinking decreased mIPSC frequency in the putamen regardless of age of onset. In the caudate, an ethanol drinking-induced increase in mIPSC frequency was only observed in monkeys that began drinking as young adults. Glutamatergic transmission did not differ between the dorsal striatal subregions in controls. With chronic ethanol drinking there was a decrease in the postsynaptic characteristics of rise time and area of mEPSCs in the putamen but an increase in mEPSC frequency in the caudate. Together, the observed changes in striatal physiology indicate a combined disinhibition due to youth and ethanol leading to abnormally strong activation of the putamen that could contribute to the increased risk for problem drinking in younger drinkers.

Effect of repeated abstinence on chronic ethanol self-administration in the rhesus monkey

RATIONALE

Abstinence-based approaches to treating alcohol use disorder (AUD) are highly prevalent, but abstinence from chronic drinking may exacerbate subsequent levels of alcohol intake in relapse.

OBJECTIVE

Use a non-human primate model that encompasses a range of chronic voluntary ethanol drinking to isolate biological responses to repeated cycles of imposed abstinence as a function of baseline voluntary alcohol drinking levels.

METHODS

Over a 26-month protocol, young adult male rhesus macaques were first induced to drink alcohol and then given continuous access to 4% (w/v) ethanol (n = 8) or water (n = 4) for approximately 14 months, followed by three 28- to 35-day abstinence phases, with 3 months of ethanol access in between. Ethanol intake and blood ethanol concentration (BEC) were the primary dependent variables. Observational signs of physical dependence and circulating ACTH and cortisol were monitored.

RESULTS

Prior to abstinence, stable, categorical, individual differences in voluntary ethanol intake under chronic access conditions were found. Following abstinence, categorical "non-heavy" drinking subjects increased drinking transiently (increased between 0.7 and 1.4 g/kg/day in first month after abstinence) but returned to baseline after 3 months. Categorical "heavy" drinkers, however, maintained drinking 1.0-2.6 g/kg above baseline for over 3 months following abstinence. Signs of physical dependence were rare, although huddling and social withdrawal increased in ethanol and control subjects. The most prominent effect on hormonal measures was heightened cortisol during abstinence that increased to a greater extent in ethanol subjects.

CONCLUSION

Involuntary abstinence increases drinking in the absence of overt physical withdrawal symptoms, and heavy drinkers are more robustly affected compared to non-heavy drinkers.

On the relationships in rhesus macaques between chronic ethanol consumption and the brain transcriptome

This is the first description of the relationship between chronic ethanol self-administration and the brain transcriptome in a non-human primate (rhesus macaque). Thirty-one male animals self-administered ethanol on a daily basis for over 12 months. Gene transcription was quantified with RNA-Seq in the central nucleus of the amygdala (CeA) and cortical Area 32. We constructed coexpression and cosplicing networks, and we identified areas of preservation and areas of differentiation between regions and network types. Correlations between intake and transcription included largely distinct gene sets and annotation categories across brain regions and between expression and splicing; positive and negative correlations were also associated with distinct annotation groups. Membrane, synaptic and splicing annotation categories were over-represented in the modules (gene clusters) enriched in positive correlations (CeA); our cosplicing analysis further identified the genes affected only at the exon inclusion level. In the CeA coexpression network, we identified Rab6b, Cdk18 and Igsf21 among the intake-correlated hubs, while in the Area 32, we identified a distinct hub set that included Ppp3r1 and Myeov2. Overall, the data illustrate that excessive ethanol self-administration is associated with broad expression and splicing mechanisms that involve membrane and synapse genes.

Higher pretreatment blood pressure is associated with greater alcohol drinking reduction in alcohol-dependent individuals treated with doxazosin

BACKGROUND

Preclinical and clinical research suggest that the α₁ receptor antagonist prazosin reduces alcohol consumption. Furthermore, clinical studies indicate a role for prazosin in treating Post-Traumatic Stress Disorder (PTSD) symptoms and a recent trial suggested that pre-treatment blood pressure (BP) predicts therapeutic response for prazosin in PTSD patients. Whether pre-treatment BP may predict response to α₁ blockers in alcohol-dependent (AD) patients is unknown. We previously reported a randomized controlled trial (RCT) where doxazosin, an α₁ receptor antagonist with a more favorable pharmacokinetic profile than prazosin, reduced drinks per week (DPW) and heavy drinking days (HDD) in AD patients with a high family history density of alcoholism. In this study, we tested pre-treatment BP as another potentially valuable clinical moderator of doxazosin's response on alcohol consumption.

METHODS

This was a double-blind placebo-controlled RCT testing doxazosin up to 16mg/day in AD treatment-seeking patients (N=41). The hypothesized moderator effect of baseline standing systolic and diastolic BP on DPW and HDD was tested.

RESULTS

With pre-treatment standing diastolic BP as a moderator, there were significant BP x medication interactions for both DPW [**p=0.009, d=0.80] and HDD [*p=0.018, d=1.11]. Post-hoc analyses indicated significant doxazosin effects in patients with higher standing BP in reducing both DPW and HDD.

CONCLUSION

These findings suggest that higher standing diastolic BP at baseline (pre-treatment) may represent a predictor of doxazosin's response on alcohol consumption in AD patients. These results further elucidate the possible efficacy and mechanisms of action of α₁ receptor antagonism in AD individuals.

Studies using macaque monkeys to address excessive alcohol drinking and stress interactions

The use of non-human primates (NHPs) in studies of volitional, oral self-administration of alcohol can help address the complex interplay between stress and excessive alcohol consumption. There are aspects to brain, endocrine and behavior of NHPs, particularly macaques, that provide a critical translational link towards understanding the risks and consequences of alcohol use disorders (AUDs) in humans. These include wide individual differences in escalating daily alcohol intake, accurate measures of hypothalamic-pituitary-adrenal (HPA) axis hormonal interactions, neuroanatomical specificity of synaptic adaptations to chronic alcohol, genetic similarities to humans, and the ability to conduct in vivo brain imaging. When placed in a framework that alcohol addiction is a sequence of dysregulations in motivational circuitry associated with severity of AUD, the NHP can provide within-subject information on both risks for and consequences of repeatedly drinking to intoxication. Notably, long-term adaptations in neurocircuitry that mediate behavioral reinforcement, stress responses and executive functions are possible with NHPs. We review here the substantial progress made using NHPs to address the complex relationship between alcohol and stress as risk factors and consequences of daily drinking to intoxication. This review also highlights areas where future studies of brain and HPA axis adaptations are needed to better understand the mechanisms involved in stress leading to excessive alcohol consumption. This article is part of the Special Issue entitled "Alcoholism".

Identifying Future Drinkers: Behavioral Analysis of Monkeys Initiating Drinking to Intoxication is Predictive of Future Drinking Classification

BACKGROUND

The Monkey Alcohol Tissue Research Resource (MATRR) is a repository and analytics platform for detailed data derived from well-documented nonhuman primate (NHP) alcohol self-administration studies. This macaque model has demonstrated categorical drinking norms reflective of human drinking populations, resulting in consumption pattern classifications of very heavy drinking (VHD), heavy drinking (HD), binge drinking (BD), and low drinking (LD) individuals. Here, we expand on previous findings that suggest ethanol drinking patterns during initial drinking to intoxication can reliably predict future drinking category assignment.

METHODS

The classification strategy uses a machine-learning approach to examine an extensive set of daily drinking attributes during 90 sessions of induction across 7 cohorts of 5 to 8 monkeys for a total of 50 animals. A Random Forest classifier is employed to accurately predict categorical drinking after 12 months of self-administration.

RESULTS

Predictive outcome accuracy is approximately 78% when classes are aggregated into 2 groups, "LD and BD" and "HD and VHD." A subsequent 2-step classification model distinguishes individual LD and BD categories with 90% accuracy and between HD and VHD categories with 95% accuracy. Average 4-category classification accuracy is 74%, and provides putative distinguishing behavioral characteristics between groupings.

CONCLUSIONS

We demonstrate that data derived from the induction phase of this ethanol self-administration protocol have significant predictive power for future ethanol consumption patterns. Importantly, numerous predictive factors are longitudinal, measuring the change of drinking patterns through 3 stages of induction. Factors during induction that predict future heavy drinkers include being younger at the time of first intoxication and developing a shorter latency to first ethanol drink. Overall, this analysis identifies predictive characteristics in future very heavy drinkers that optimize intoxication, such as having increasingly fewer bouts with more drinks. This analysis also identifies characteristic avoidance of intoxicating topographies in future low drinkers, such as increasing number of bouts and waiting longer before the first ethanol drink.

Adaptations in Basal and Hypothalamic-Pituitary-Adrenal-Activated Deoxycorticosterone Responses Following Ethanol Self-administration in Cynomolgus Monkeys

Acute ethanol activates the hypothalamic-pituitary-adrenal (HPA) axis, while long-term exposure results in a blunted neuroendocrine state, particularly with regards to the primary endpoint, cortisol, the primary glucocorticoid produced in the adrenal cortex. However, it is unknown if this dampened neuroendocrine status also influences other adrenocortical steroids. Plasma concentration of the mineralocorticoid and neuroactive steroid precursor deoxycorticosterone (DOC) is altered by pharmacological challenges of the HPA axis in cynomolgus monkeys. The present study investigated HPA axis regulation of circulating DOC concentration over the course of ethanol (4% w/v) induction and self-administration in non-human primates (Macaca fasciculata, n = 10). Plasma DOC, measured by radioimmunoassay, was compared at baseline (ethanol naïve), during schedule-induced polydipsia, and following 6-months of 22 h/day access to ethanol and water. The schedule induction of ethanol drinking did not alter basal DOC levels but selectively dampened the DOC response to pharmacological challenges aimed at the anterior pituitary (ovine corticotrophin-releasing hormone) and adrenal gland (post-dexamethasone adrenocorticotropin hormone), while pharmacological inhibition of central opioid receptors with naloxone greatly enhanced the DOC response during induction. Following 6 months of ethanol self-administration, basal DOC levels were increased more than twofold, while responses to each of the challenges normalized somewhat but remained significantly different than baseline. These data show that HPA axis modulation of the neuroactive steroid precursor DOC is markedly altered by the schedule induction of ethanol drinking and long-term voluntary ethanol self-administration. The consequences of chronic ethanol consumption on HPA axis regulation of DOC point toward allostatic modification of hypothalamic and adrenal function.

Effects of chronic alcohol consumption on neuronal function in the non-human primate BNST

Alterations in hypothalamic-pituitary-adrenal axis function contribute to many of the adverse behavioral effects of chronic voluntary alcohol drinking, including alcohol dependence and mood disorders; limbic brain structures such as the bed nucleus of the stria terminalis (BNST) may be key sites for these effects. Here, we measured circulating levels of several steroid hormones and performed whole-cell electrophysiological recordings from acutely prepared BNST slices of male rhesus monkeys allowed to self-administer alcohol for 12 months or a control solution. Initial comparisons revealed that BNST neurons in alcohol-drinking monkeys had decreased membrane resistance, increased frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) with no change in spontaneous excitatory postsynaptic currents (sEPSCs). We then used a combined variable cluster analysis and linear mixed model statistical approach to determine whether specific factors including stress and sex hormones, age and measures of alcohol consumption and intoxication are related to these BNST measures. Modeling results showed that specific measures of alcohol consumption and stress-related hormone levels predicted differences in membrane conductance in BNST neurons. Distinct groups of adrenal stress hormones were negatively associated with the frequency of sIPSCs and sEPSCs, and alcohol drinking measures and basal neuronal membrane properties were additional positive predictors of inhibitory, but not excitatory, PSCs. The amplitude of sEPSCs was highly positively correlated with age, independent of other variables. Together, these results suggest that chronic voluntary alcohol consumption strongly influences limbic function in non-human primates, potentially via interactions with or modulation by other physiological variables, including stress steroid hormones and age.

An ultrastructural analysis of the effects of ethanol self-administration on the hypothalamic paraventricular nucleus in rhesus macaques

A bidirectional relationship between stress and ethanol exists whereby stressful events are comorbid with problematic ethanol use and prolonged ethanol exposure results in adaptations of the physiological stress response. Endocrine response to stress is initiated in the hypothalamic paraventricular nucleus (PVN) with the synthesis and release of corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP). Alterations in CRH and AVP following long-term ethanol exposure in rodents is well demonstrated, however little is known about the response to ethanol in primates or the mechanisms of adaptation. We hypothesized that long-term ethanol self-administration in nonhuman primates would lead to ultrastructural changes in the PVN underlying adaptation to chronic ethanol. Double-label immunogold electron microscopy (EM) was used to measure presynaptic gamma-aminobutyric acid (GABA) and glutamate density within synaptic terminals contacting CRH- and AVP-immunoreactive dendrites. Additionally, pituitary-adrenal hormones (ACTH, cortisol, DHEA-s and aldosterone) under two conditions (low and mild stress) were compared before and after self-administration. All hormones were elevated in response to the mild stressor independent of ethanol consumption. The presynaptic glutamate density in recurrent (i.e., intra-hypothalamic) CRH terminals was highly related to ethanol intake, and may be a permissive factor in increased drinking due to stress. Conversely, glutamate density within recurrent AVP terminals showed a trend-level increase following ethanol, but was not related to average daily consumption. Glutamate density in non-recurrent AVP terminals was related to aldosterone under the low stress condition while GABAergic density in this terminal population was related to water consumption. The results reveal distinct populations of presynaptic terminals whose glutamatergic or GABAergic density were uniquely related to water and ethanol consumption and circulating hormones.

Twelve months of voluntary heavy alcohol consumption in male rhesus macaques suppresses intracortical bone remodeling

Chronic heavy alcohol consumption is a risk factor for cortical bone fractures in males. The increase in fracture risk may be due, in part, to reduced bone quality. Intracortical (osteonal) bone remodeling is the principle mechanism for maintaining cortical bone quality. However, it is not clear how alcohol abuse impacts intracortical bone remodeling. This study investigated the effects of long-duration heavy alcohol consumption on intracortical bone remodeling in a non-human primate model. Following a 4-month induction period, male rhesus macaques (Macaca mulatta, n=21) were allowed to voluntarily self-administer water or alcohol (4% ethanol w/v) for 22h/d, 7 d/wk for 12months. Control monkeys (n=13) received water and an isocaloric maltose-dextrin solution. Tetracycline hydrochloride was administered orally 17 and 3days prior to sacrifice for determination of active mineralization sites. Animals in the alcohol group consumed 2.7±0.2g alcohol/kg/d (mean±SE) during the 12months of self-administration, resulting in a mean daily blood alcohol concentration of 77±9mg/dl from samples taken at 7h after the start of a daily session. However, blood alcohol concentration varied widely from day to day, with peak levels exceeding 250mg/dl, modeling a binge-drinking pattern of alcohol consumption. The skeletal response to alcohol was determined by densitometry, microcomputed tomography and histomorphometry. Significant differences in tibial bone mineral content, bone mineral density, and cortical bone architecture (cross-sectional volume, cortical volume, marrow volume, cortical thickness, and polar moment of inertia) in the tibial diaphysis were not detected with treatment. However, cortical porosity was lower (1.8±0.5 % versus 0.6±0.1 %, p=0.021) and labeled osteon density was lower (0.41±0.2/mm(2)versus 0.04±0.01/mm(2), p<0.003) in alcohol-consuming monkeys compared to controls, indicating a reduced rate of intracortical bone remodeling. In concordance, plasma CTx was lower (2.5±0.3ng/ml versus 1.7±0.1ng/ml, p=0.028) in the alcohol group. These results suggest that chronic heavy alcohol consumption may negatively impact bone health, in part, by suppressing intracortical bone remodeling.

Alcohol's Burden on Immunity Following Burn, Hemorrhagic Shock, or Traumatic Brain Injury

Alcohol consumption contributes to increased incidence and severity of traumatic injury. Compared with patients who do not consume alcohol, alcohol-consuming patients have higher rates of long-term morbidity and mortality during recovery from injury. This can be attributed in part to an impaired immune response in individuals who consume alcohol. Acute and chronic alcohol use can affect both the innate and adaptive immune defense responses within multiple organ systems; the combination of alcohol use and injury results in increased susceptibility to bacterial and viral pathogens. This review examines the major deleterious effects of alcohol on immunity following tissue damage or traumatic injury, with a focus on alcohol's influence on the ability of the immune and major organ systems to fight disease and to repair damaged tissues following injury.