Brain Ethanol Research Articles

P-26 * CHANGE IN ALDEHYDE DEHYDROGENASE BY CHRONIC TREATMENT WITH ETHANOL IN THE MOUSE BRAIN

Acute and chronic consumption of ethanol induces a modification of molecular events such as release of neurotransmitter, receptors function, and intracellular signal transduction systems. Furthermore, such alterations would change dopamine response in the mesolimbic dopaminergic system projecting to the nucleus accumbence and prefrontal cortex from the ventral tegmental area. It is known that ethanol is metabolized at the liver to acetaldehyde, and further metabolized to acetate, however, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) also exist in the brain. In this study, we hypothesized that metabolism of ethanol in the brain could be related to ethanol dependence. Firstly, we confirmed that the mRNAs of ADH and ALDH are existing as metabolic enzyme of ethanol in mouse brain. The protein levels of ALDH in the ventral tegmental area were significantly increased by chronic treatment with ethanol. On the other hand, chronic treatment with ethanol enhanced the rewarding effects of ethanol. This enhancement of the rewarding effects of ethanol by chronic treatment with ethanol was significantly inhibited by i.c.v. administration of the ALDH2 inhibitor disulfiram. The present study implicated that the metabolism of ethanol in the brain may regulate the alteration of dopamine response by treatment with ethanol.

The renaissance of acetaldehyde as a psychoactive compound: decades in the making.

The renaissance of acetaldehyde as a psychoactive compound: decades in the making.

Metabolic products of [2-(13) C]ethanol in the rat brain after chronic ethanol exposure.

Most ingested ethanol is metabolized in the liver to acetaldehyde and then to acetate, which can be oxidized by the brain. This project assessed whether chronic exposure to alcohol can increase cerebral oxidation of acetate. Through metabolism, acetate may contribute to long-term adaptation to drinking. Two groups of adult male Sprague-Dawley rats were studied, one treated with ethanol vapor and the other given room air. After 3weeks the rats received an intravenous infusion of [2-(13) C]ethanol via a lateral tail vein for 2h. As the liver converts ethanol to [2-(13) C]acetate, some of the acetate enters the brain. Through oxidation the (13) C is incorporated into the metabolic intermediate α-ketoglutarate, which is converted to glutamate (Glu), glutamine (Gln), and GABA. These were observed by magnetic resonance spectroscopy and found to be (13) C-labeled primarily through the consumption of ethanol-derived acetate. Brain Gln, Glu, and, GABA (13) C enrichments, normalized to (13) C-acetate enrichments in the plasma, were higher in the chronically treated rats than in the ethanol-naïve rats, suggesting increased cerebral uptake and oxidation of circulating acetate. Chronic ethanol exposure increased incorporation of systemically derived acetate into brain Gln, Glu, and GABA, key neurochemicals linked to brain energy metabolism and neurotransmission. The liver converts ethanol to acetate, which may contribute to long-term adaptation to drinking. Astroglia oxidize acetate and generate neurochemicals, while neurons and glia may also oxidize ethanol. When (13) C-ethanol is administered intravenously, (13) C-glutamine, glutamate, and GABA, normalized to (13) C-acetate, were higher in chronic ethanol-exposed rats than in control rats, suggesting that ethanol exposure increases cerebral oxidation of circulating acetate.

English

Introduction In the past few decades, ethanol has assumed the role of the most widespread psychotropic agent in Western society because of its availability to the youth and adults and also because it is generally considered legal in many societies. It is known that the alcohol can have significant relapses on the central nervous system; hence, there is a need for monitoring the toxicokinetics and the effects of ethanol on the brain with the most appropriate techniques. Among the techniques that aim to measure ethanol concentration in the brain, microdialysis has been the most widely used, but because of its invasiveness, associated with low temporal resolution, and the necessity of using connecting tubes to carry out the experiments, it is not particularly suitable for clinical trials. Recently, electrochemical biosensors, also minimally invasive, have been developed, which offer the possibility of monitoring the real-time variations of ethanol concentrations in the brain of animal models due to the very small dimensions of the transducer electrode. Recently, non-invasive methods have been used for the direct monitoring of alcohol in the brain, which use spectroscopic techniques such as magnetic resonance spectroscopy and magnetic resonance imaging or positron emission tomography, which are principally used to monitor ethanol metabolites. The aim of this review is to discuss all the techniques used to monitor brain ethanol and highlight their strengths and weaknesses. Conclusion Microdialysis and biosensors are primarily used in preclinical studies; both are very reliable techniques, but for invasiveness, they can only be used in animal models. Alternatively, spectroscopic techniques are suitable for both preclinical and clinical studies, and are not exclusive for animal models.

Oxidation of ethanol in the rat brain and effects associated with chronic ethanol exposure

It has been reported that chronic and acute alcohol exposure decreases cerebral glucose metabolism and increases acetate oxidation. However, it remains unknown how much ethanol the living brain can oxidize directly and whether such a process would be affected by alcohol exposure. The questions have implications for reward, oxidative damage, and long-term adaptation to drinking. One group of adult male Sprague-Dawley rats was treated with ethanol vapor and the other given room air. After 3 wk the rats received i.v. [2-(13)C]ethanol and [1, 2-(13)C2]acetate for 2 h, and then the brain was fixed, removed, and divided into neocortex and subcortical tissues for measurement of (13)C isotopic labeling of glutamate and glutamine by magnetic resonance spectroscopy. Ethanol oxidation was seen to occur both in the cortex and the subcortex. In ethanol-naïve rats, cortical oxidation of ethanol occurred at rates of 0.017 ± 0.002 µmol/min/g in astroglia and 0.014 ± 0.003 µmol/min/g in neurons, and chronic alcohol exposure increased the astroglial ethanol oxidation to 0.028 ± 0.002 µmol/min/g (P = 0.001) with an insignificant effect on neuronal ethanol oxidation. Compared with published rates of overall oxidative metabolism in astroglia and neurons, ethanol provided 12.3 ± 1.4% of cortical astroglial oxidation in ethanol-naïve rats and 20.2 ± 1.5% in ethanol-treated rats. For cortical astroglia and neurons combined, the ethanol oxidation for naïve and treated rats was 3.2 ± 0.3% and 3.8 ± 0.2% of total oxidation, respectively. (13)C labeling from subcortical oxidation of ethanol was similar to that seen in cortex but was not affected by chronic ethanol exposure.

Chronic Ethanol (EtOH) Consumption Differentially Alters Gray and White Matter EtOH Methyl 1H Magnetic Resonance Intensity in the Primate Brain

In vivo magnetic resonance spectroscopy (MRS) has previously been used to directly monitor brain ethanol (EtOH). It has been proposed that the EtOH methyl ¹H resonance intensity is larger in EtOH-tolerant individuals than in sensitive individuals. To characterize the relationship between long-term EtOH exposure and the brain EtOH MRS intensity, we present data from a longitudinal experiment conducted using nonhuman primate subjects. In vivo MRS was used to measure the gray matter (GM) and white matter (WM) EtOH methyl ¹H MRS intensity in 18 adult male rhesus macaques at 4 time points throughout the course of a chronic drinking experiment. Time points were prior to EtOH drinking, following a 3-month EtOH induction procedure, and following 6, and 12 subsequent months of 22 h/d of "open access" to EtOH (4% w/v) and water. The EtOH methyl ¹H MRS intensity, which we observed to be independent of age over the range examined, increased with chronic EtOH exposure in GM and WM. In GM, MRS intensity increased from naïve level following the EtOH induction period (90 g/kg cumulative EtOH intake). In WM, MRS intensity was not significantly different from the EtOH-naïve state until after 6 months of 22-hour free access (110 to 850 g/kg cumulative intake range). The WM MRS intensity in the EtOH-naïve state was positively correlated with future drinking, and the increase in WM MRS intensity was negatively correlated with the amount of EtOH consumed throughout the experiment. Chronic exposure to EtOH is associated with brain changes that result in differential increases in EtOH MRS intensity in GM and WM. The EtOH-naïve WM MRS intensity pattern is consistent with its previously proposed relationship to innate tolerance to the intoxicating effects of EtOH. EtOH-dependent MRS intensity changes in GM required less EtOH exposure than was necessary to produce changes in WM. Within WM, an unexpected, potentially age dependent, enhanced sensitivity to EtOH in light drinkers relative to heavy drinkers was observed.

Development and Characterization of an Implantable Biosensor for Telemetric Monitoring of Ethanol in the Brain of Freely Moving Rats

Ethanol is one of the most widespread psychotropic agents in western society. While its psychoactive effects are mainly associated with GABAergic and glutamatergic systems, the positive reinforcing properties of ethanol are related to activation of mesolimbic dopaminergic pathways resulting in a release of dopamine in the nucleus accumbens. Given these neurobiological implications, the detection of ethanol in brain extracellular fluid (ECF) is of great importance. In this study, we describe the development and characterization of an implantable biosensor for the amperometric detection of brain ethanol in real time. Ten different designs were characterized in vitro in terms of Michaelis-Menten kinetics (V(MAX) and K(M)), sensitivity (linear region slope, limit of detection (LOD), and limit of quantification (LOQ)), and electroactive interference blocking. The same parameters were monitored in selected designs up to 28 days after fabrication in order to quantify their stability. Finally, the best performing biosensor design was selected for implantation in the nucleus accumbens and coupled with a previously developed telemetric device for the real-time monitoring of ethanol in freely moving, untethered rats. Ethanol was then administered systemically to animals, either alone or in combination with ranitidine (an alcohol dehydrogenase inhibitor) while the biosensor signal was continuously recorded. The implanted biosensor, integrated in the low-cost telemetry system, was demonstrated to be a reliable device for the short-time monitoring of exogenous ethanol in brain ECF and represents a new generation of analytical tools for studying ethanol toxicokinetics and the effect of drugs on brain ethanol levels.

Repeated cycles of chronic intermittent ethanol exposure leads to the development of tolerance to aversive effects of ethanol in C57BL/6J mice.

Repeated cycles of chronic intermittent ethanol (CIE) exposure lead to increased voluntary ethanol (EtOH) intake in C57BL/6J mice. This study evaluates the development of tolerance to EtOH's aversive effects in CIE exposure. Adult male C57BL/6J mice were trained to drink 15% EtOH (vs. water) in a limited access procedure and then exposed to CIE (EtOH mice) or air (control [CTL] mice) for 5 cycles alternating with weekly access to EtOH drinking. Following the 4th CIE cycle, the aversive effects of EtOH were evaluated using a conditioned taste aversion (CTA) paradigm with 1% saccharin as the conditioned stimulus. Several doses of EtOH (0, 1, 2, and 3 g/kg) and LiCl (0.4 M, 0.02 ml/g) served as unconditioned stimuli. Finally, mice underwent a 5th CIE cycle to measure blood and brain concentrations following a 2 g/kg EtOH dose. CIE exposure increased EtOH drinking in EtOH mice while drinking in CTL mice remained stable. The lowest EtOH dose (1 g/kg) did not induce CTA in either group, but the highest dose (3 g/kg) produced CTA in both groups (49% reduction for CTL vs. 25% reduction for EtOH) although the group differences were not statistically significant. However, the 2 g/kg EtOH dose induced a significant aversion in CTL mice (27% reduction) but not in EtOH mice (20% increase), indicating tolerance to EtOH's aversive effects. LiCl caused a similar aversion in CTL and EtOH mice (50% reduction). Finally, blood and brain ethanol concentrations were not different between CTL and EtOH mice following a 2 g/kg EtOH dose. The data indicate that CIE exposure produces tolerance to the aversive effects of 2 g/kg EtOH. This effect does not appear to be related to a learning deficit or altered EtOH pharmacokinetics. These data support the notion that tolerance to EtOH's aversive effects may contribute to excessive EtOH drinking in EtOH-dependent mice.

NADPH oxidase and reactive oxygen species contribute to alcohol-induced microglial activation and neurodegeneration

BackgroundActivation of microglia causes the production of proinflammatory factors and upregulation of NADPH oxidase (NOX) that form reactive oxygen species (ROS) that lead to neurodegeneration. Previously, we reported that 10 daily doses of ethanol treatment induced innate immune genes in brain. In the present study, we investigate the effects of chronic ethanol on activation of NOX and release of ROS, and their contribution to ethanol neurotoxicity.MethodsMale C57BL/6 and NF-κB enhanced GFP mice were treated intragastrically with water or ethanol (5 g/kg, i.g., 25% ethanol w/v) daily for 10 days. The effects of chronic ethanol on cell death markers (activated caspase-3 and Fluoro-Jade B), microglial morphology, NOX, ROS and NF-κB were examined using real-time PCR, immunohistochemistry and hydroethidine histochemistry. Also, Fluoro-Jade B staining and NOX gp91phox immunohistochemistry were performed in the orbitofrontal cortex (OFC) of human postmortem alcoholic brain and human moderate drinking control brain.ResultsEthanol treatment of C57BL/6 mice showed increased markers of neuronal death: activated caspase-3 and Fluoro-Jade B positive staining with Neu-N (a neuronal marker) labeling in cortex and dentate gyrus. The OFC of human post-mortem alcoholic brain also showed significantly more Fluoro-Jade B positive cells colocalized with Neu-N, a neuronal marker, compared to the OFC of human moderate drinking control brain, suggesting increased neuronal death in the OFC of human alcoholic brain. Iba1 and GFAP immunohistochemistry showed activated morphology of microglia and astrocytes in ethanol-treated mouse brain. Ethanol treatment increased NF-κB transcription and increased NOX gp91phox at 24 hr after the last ethanol treatment that remained elevated at 1 week. The OFC of human postmortem alcoholic brain also had significant increases in the number of gp91phox + immunoreactive (IR) cells that are colocalized with neuronal, microglial and astrocyte markers. In mouse brain ethanol increased gp91phox expression coincided with increased production of O2- and O2- - derived oxidants. Diphenyleneiodonium (DPI), a NOX inhibitor, reduced markers of neurodegeneration, ROS and microglial activation.ConclusionsEthanol activation of microglia and astrocytes, induction of NOX and production of ROS contribute to chronic ethanol-induced neurotoxicity. NOX-ROS and NF-κB signaling pathways play important roles in chronic ethanol-induced neuroinflammation and neurodegeneration.

Intravenous Ethanol Infusion Decreases Human Cortical γ-Aminobutyric Acid and N-Acetylaspartate as Measured with Proton Magnetic Resonance Spectroscopy at 4 Tesla

Ethanol modulates glutamate and γ-aminobutyric (GABA) function. However, little is known about the acute pharmacologic effects of ethanol on levels of GABA, glutamate, and other metabolites measurable in the human cortex in vivo with proton magnetic resonance spectroscopy ((1)H-MRS). Eleven healthy social drinkers received two intravenous ethanol infusions that raised breath alcohol levels to a clamped plateau of 60 mg/dL over 60-70 min. The first infusion established tolerability of the procedure, and the second procedure, conducted 15 ± 12 days later, was performed during (1)H-MRS of occipital GABA, glutamate, and other metabolites. The time course of brain ethanol approximated that of breath ethanol, but venous ethanol lagged by approximately 7 min. The GABA fell 13 ± 8% after 5 min of the ethanol infusion and remained reduced (p = .003) throughout the measurement. The combination of N-acetylaspartate and N-acetylaspartyl glutamate (summed as NAA) fell steadily during the infusion by 8 ± 3% (p = .0036). Ethanol reduced cortical GABA and NAA levels in humans. Reductions in GABA levels are consistent with facilitation of GABA(A) receptor function by ethanol. The gradual decline in NAA levels suggests inhibition of neural or metabolic activity in the brain.

Different chronic ethanol exposure regimens in adolescent and adult male rats: Effects on tolerance to ethanol-induced motor impairment

Findings are mixed regarding the expression of tolerance after repeated ethanol exposure, perhaps in part due to dose/frequency variations in exposure regimens. The present study compared age-related differences in tolerance development following 10 days of 1 g/kg twice daily, 2 g/kg once daily, or intermittent 4 g/kg ethanol exposure regimens. To measure expression of chronic tolerance and acute tolerance, ethanol-induced motor impairment was assessed on day 12, with functionally equivalent ethanol doses administered across age (2 g/kg – adolescents; 1.5 g/kg – adults). Subsequent challenge doses resulted in lower brain ethanol concentrations in both age groups as a function of the chronic ethanol regimens. Expected age-related differences emerged in acute tolerance expression in non-manipulated animals, with adolescents, but not adults showing acute tolerance. Regimens sufficient to induce alterations in ethanol metabolism did not result in chronic functional tolerance at either age, although chronic injections were sufficient to induce acute tolerance in adults.

Chlorpromazine Protects Against Apoptosis Induced by Exogenous Stimuli in the Developing Rat Brain

BackgroundChlorpromazine (CPZ), a commonly used antipsychotic drug, was found to play a neuroprotective role in various models of toxicity. However, whether CPZ has the potential to affect brain apoptosis in vivo is still unknown. The purpose of this study was to investigate the potential effect of CPZ on the apoptosis induced by exogenous stimuli.MethodologyThe ethanol treated infant rat was utilized as a valid apoptotic model, which is commonly used and could trigger robust apoptosis in brain tissue. Prior to the induction of apoptosis by subcutaneous injection of ethanol, 7-day-old rats were treated with CPZ at several doses (5 mg/kg, 10 mg/kg and 20 mg/kg) by intraperitoneal injection. Apoptotic cells in the brain were measured using TUNEL analysis, and the levels of cleaved caspase-3, cytochrome c, the pro-apoptotic factor Bax and the anti-apoptotic factor Bcl-2 were assessed by immunostaining or western blot.FindingsCompared to the group injected with ethanol only, the brains of the CPZ-pretreated rats had fewer apoptotic cells, lower expression of cleaved caspase-3, cytochrome c and Bax, and higher expression of Bcl-2. These results demonstrate that CPZ could prevent apoptosis in the brain by regulating the mitochondrial pathway.ConclusionsCPZ exerts an inhibitory effect on apoptosis induced by ethanol in the rat brain, intimating that it may offer a means of protecting nerve cells from apoptosis induced by exogenous stimuli.

Age Differences in the Expression of Acute and Chronic Tolerance to Ethanol in Male and Female Rats

Ontogenetic differences in response to ethanol (EtOH) challenge have been observed under a variety of circumstances, including varying reports of developmental differences in the expression of tolerance to EtOH. The purpose of the present experiment was to further explore potential differences in acute (AT) and chronic (CT) tolerance expression between adolescent and adult, male and female Sprague-Dawley rats, using the social interaction test. AT and CT to the social suppressing effects of a moderate dose of EtOH was assessed in adolescent and adult rats following intraperitoneal injections of 2.0 g/kg EtOH or saline daily for 10 days. At test, adults and adolescents were challenged with 1.0 or 1.25 g/kg EtOH, respectively, with AT and CT assessed at 5 and 25 minutes postinjection using ratios of impairment to brain ethanol concentrations (BrECs) at each time period (CT) and within-session declines in impairment relative to BrECs (AT). In adolescents, 10 days of EtOH pre-exposure resulted in evidence of CT at 25 minutes postinjection, perhaps associated with an enhanced expression of AT. Among adults, signs of CT were seen at 5 minutes postinjection in adults, and may reflect neuroadaptations unassociated with AT, as with evidence of tolerance emerging only in adult control animals repeatedly exposed to saline injection prior to EtOH challenge on test day. Sex differences in tolerance expression were not observed at either age. Our results show ontogenetic differences between adolescents and adults in the short- and long-term neuroadaptations that they express in response to repeated perturbations with EtOH. Together these findings add age of exposure and time of testing within the intoxication period as critical variables to be considered when exploring the complex relationship between AT and CT.

Ethanol induces second-order aversive conditioning in adolescent and adult rats

Alcohol abuse and dependence are considered public health problems, with an etiological onset often occurring during late childhood and adolescence, and understanding age-related differences in ethanol sensitivity is important. Low to moderate ethanol doses (0.5 and 2.0 g/kg, intragastrically [i.g.]) induce single-trial, appetitive second-order place conditioning (SOC) in adolescent, but not adult, rats. Recent studies have demonstrated that adolescents may be less sensitive than adults to the aversive properties of ethanol, reflected by conditioned taste aversion. The present study assessed the aversive motivational effects of high-dose ethanol (3.0 and 3.25 g/kg, i.g., for adolescents and adults, respectively) using SOC. Experiment 1 revealed similar blood and brain ethanol levels in adolescent and adult rats given 3.0 and 3.25 g/kg ethanol, respectively. In Experiment 2, animals received ethanol or vehicle paired with intraoral pulses of sucrose (conditioned stimulus 1 [CS1]). After one, two, or three conditioning trials, the rats were presented with the CS1 while in a distinctive chamber (CS2). When tested for CS2 preference, ethanol-treated animals exhibited reduced preference for the CS2 compared with controls. This result, indicative of ethanol-mediated aversive place conditioning, was similar for adolescents and adults; for females and males; and after one, two, or three training trials. In conjunction with previous results, the present study showed that, in adolescent rats subjected to SOC, ethanol’s hedonic effects vary from appetitive to aversive as the ethanol dose increases. Adolescent and adult animals appear to perceive the postingestive effects of high-dose ethanol as similarly aversive when assessed by SOC.

P03-227 - The bi-conceptional model of brain's ethanol effect

IntroductionTo identify a general view of the effect of alcohol on brain's functions, we developed a model that identifies the effect of underlying biochemical products of ethanol and its metabolites on brain functions.AimTo provide a general model for explaining alcohol effect on brain functions.Materials and methodsPeer reviewed materials from Pubmed, Index Medicus, Elsevier from the year 1950 to April 2009 on the effect of ethanol at varying doses on the functions of the brain and liver were examined.Results and conclusionThe bi-conception model of brain's ethanol effect holds that the effects that results from the intake of alcohol even in moderate doses is the resultant effect of hypoglycemic condition (inhibition of glyconeogenesis by increase in NADH/NAD and Lactate/pyruvate ratio) as well as direct effect of ethanol to the brain. Disglycemic control results in many alcohol related effect - like hyperketosis, steatosis, hepatitis, liver cirrhosis etc. Coagulopathy from liver dysfunction is also a major reason for the brain's ethanol effect. The resultant effect (dose-time-dependent effect) on brain functions might be ADHD, various psycho-dysfunctions etc. The extent of hypoglycemia predicts the capacity of neuronal functions.

Effect of catalase activators and inhibitors on ethanol pharmacokinetic parameteres and ethanol and aldehyde-metabolizing enzyme activities in the rat liver and brain

The effects of catalase regulators (aminotriazole, lead acetate, taurine, di-2-ethylhexylphthalate) on the preference for ethanol, its pharmacokinetics, and activities of rat liver and brain ethanol and acetaldehyde-metabolizing enzymes were studied. Lead acetate (100 mg/kg, i.p., 7 days), aminotriazole (1 g/kg, i.p., 7 days), and taurine (650 mg/kg, i.g., 14 days) decreased ethanol consumption under conditions of free choice (10% ethanol water), whereas di-2-ethylhexylphthalate (300 mg/kg, i.g., 7 days) did not exert any effect on this parameter. Taurine, lead acetate and di-2-ethylhexylphthalate significantly activated liver ADH, MEOS and catalase peroxidase activity. Aminotriazole also activated ADH and MEOS, but inhibited liver catalase. The activities of liver and brain A1DH as well as catalase were insignificantly changed by this treatment. The 7-day administration of lead acetate, di-2-ethylhexylphthalate and aminotriazole administrations significantly influenced the ethanol (2 g/kg., i.p.) pharmacokinetic parameters: the area under the pharmacokinetic curve and the elimination half-life time were significantly reduced, whereas the elimination constant and clearance were increased. This unequivocally indicates accelerated ethanol elimination. The 14-day ingestion of taurine insignificantly changed the parameters of ethanol pharmacokinetics in rats.

Quantification of ethanol methyl 1H magnetic resonance signal intensity following intravenous ethanol administration in primate brain

In vivo 1H magnetic resonance spectroscopy (MRS) can be used to directly monitor brain ethanol. Previously, studies of human subjects have lead to the suggestion that the ethanol methyl 1H MRS signal intensity relates to tolerance to ethanol’s intoxicating effects. More recently, the ethanol 1H MRS signal intensity has been recognized to vary between brain gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF) due to differences in T 2 within these environments. The methods presented here extend ethanol MRS techniques to non-human primate subjects. Twelve monkeys were administered ethanol while sedated and positioned within a 3T MRI system. Chemical shift imaging (CSI) measurements were performed following intravenous infusion of 1 g/kg ethanol. Magnetic resonance imaging (MRI) data were also recorded for each monkey to provide volume fractions of GM, WM, and CSF for each CSI spectrum. To estimate co-variance of ethanol MRS intensity with GM, WM, and CSF volume fractions, the relative contribution of each tissue subtype was determined following corrections for radiofrequency pulse profile non-uniformity, chemical shift artifacts, and differences between the point spread function in the CSI data and the imaging data. The ethanol MRS intensity per unit blood ethanol concentration was found to differ between GM, WM, and CSF. Individual differences in MRS intensity were larger in GM than WM. This methodology demonstrates the feasibility of ethanol MRS experiments and analysis in non-human primate subjects, and suggests GM may be a site of significant variation in ethanol MRS intensity between individuals.

Repeated cycles of chronic intermittent ethanol exposure in mice increases voluntary ethanol drinking and ethanol concentrations in the nucleus accumbens

This study examined the relationship between voluntary ethanol consumption and ethanol concentrations measured in the nucleus accumbens of ethanol dependent and nondependent C57BL/6J mice. Mice were offered ethanol in a two-bottle choice; limited access paradigm and consummatory behavior was monitored with lickometers. After baseline intake stabilized, mice received chronic intermittent ethanol (EtOH group) or air (CTL group) exposure by inhalation (16 h/day for 4 days) and then resumed drinking. Brain ethanol levels during voluntary drinking were measured by microdialysis procedures and compared to brain ethanol concentrations produced during chronic intermittent ethanol vapor exposure. Voluntary ethanol consumption progressively increased over repeated cycles of chronic intermittent ethanol exposure but remained unchanged in CTL mice. Analysis of lick patterns indicated EtOH mice consumed ethanol at a faster rate compared to CTL mice. The greater and faster rate of ethanol intake in EtOH mice produced higher peak brain ethanol concentrations compared to CTL mice, and these levels were similar to levels produced during chronic intermittent ethanol exposure. These results show that in this model of dependence and relapse drinking, dependent mice exhibit enhanced voluntary ethanol consumption relative to nondependent controls, which consequently produces blood and brain ethanol concentrations similar to those experienced during chronic intermittent ethanol exposure.

Reduction in the anxiolytic effects of ethanol by centrally formed acetaldehyde: the role of catalase inhibitors and acetaldehyde-sequestering agents

Considerable evidence indicates that brain ethanol metabolism mediated by catalase is involved in modulating some of the behavioral and physiological effects of this drug, which suggests that the first metabolite of ethanol, acetaldehyde, may have central actions. Previous results have shown that acetaldehyde administered into the lateral ventricles produced anxiolysis in a novel open arena in rats. The present studies investigate the effects of centrally formed acetaldehyde on ethanol-induced anxiolysis. The effects of the catalase inhibitor sodium azide (SA; 0 or 10 mg/kg, IP) on ethanol-induced anxiolysis (0.0, 0.5, or 1.0 g/kg, IP) were evaluated in CD1 mice in two anxiety paradigms, the elevated plus maze and the dark/light box. Additional studies assessed the effect of the noncompetitive catalase inhibitor 3-amino-1,2,4-triazole (AT; 0.5 g/kg, IP) and the acetaldehyde inactivation agent D: -penicillamine (50 mg/kg, IP) on the plus maze. SA reduced the anxiolytic effects of ethanol on several parameters evaluated in the elevated plus maze and in the dark/light box. In the plus maze, AT completely blocked and D-penicillamine significantly reduced the anxiolytic properties of ethanol. Thus, when cerebral metabolism of ethanol into acetaldehyde is blocked by catalase inhibitors, or acetaldehyde is inactivated, there is a suppressive effect on the anxiolytic actions of ethanol. These data provide further support for the idea that centrally formed or administered acetaldehyde can contribute to some of the psychopharmacological actions of ethanol, including its anxiolytic properties.

The shell of the nucleus accumbens has a higher dopamine response compared with the core after non-contingent intravenous ethanol administration

Dopamine increases in the nucleus accumbens after ethanol administration in rats, but the contributions of the core and shell subregions to this response are unclear. The goal of this study was to determine the effect of various doses of i.v. ethanol infusions on dopamine in these two subregions of the nucleus accumbens. Male Long-Evans rats were infused with either acute i.v. ethanol (0.5, 1.0, 1.5 g/kg), repeated i.v. ethanol (four 1.0 g/kg infusions resulting in a cumulative dose of 4.0 g/kg), or saline as a control for each condition. Dopamine and ethanol were measured in dialysate samples from each experiment. The in vivo extraction fraction for ethanol of probes was determined using i.v. 4-methylpyrazole, and was used to estimate peak brain ethanol concentrations after the infusions. The peak brain ethanol concentrations after the 0.5, 1.0 and 1.5 g/kg ethanol infusions were estimated to be 20, 49 and 57 mM, respectively. A significant dopamine increase was observed for the 0.5 g/kg ethanol group when collapsed across subregions. However, both the 1.0 g/kg and 1.5 g/kg ethanol infusions produced significant increases in dopamine levels in the shell that were significantly higher than those in the core. An ethanol dose-response effect on dopamine in the shell was observed when saline controls, 0.5, 1.0, and 1.5 g/kg groups were compared. For the cumulative-dosing study, the first, second, and fourth infusions resulted in significant increases in dopamine in the shell. However, these responses were not significantly different from one another. The results of this study show that the shell has a stronger response than the core to i.v. ethanol, that dopamine in the shell increases in a dose-dependent manner between 0.5–1.0 g/kg doses, but that the response to higher ethanol doses reaches a plateau.