Effects of combined systemic alcohol and central nicotine administration into ventral tegmental area on dopamine release in the nucleus accumbens

BACKGROUND: Alcoholism is associated with a higher incidence of smoking. The mesolimbic dopaminergic pathway is believed to play an important role in the reinforcing effects of both ethanol and nicotine. This study was undertaken to determine whether simultaneous administration of systemic ethanol and microinjection of nicotine into the ventral tegmental area (VTA) would result in exaggerated release of dopamine (DA) in the shell region of nucleus accumbens. METHODS: Microdialysis was applied in awake, freely moving adult male Wistar rats, and DA concentration in the dialysate was measured by HPLC-electrochemical detectors. RESULTS: Systemic administration of ethanol or microinjection of nicotine into VTA resulted in a dose-dependent increase in DA release (extracellular DA concentration). Simultaneous administration of lower doses of nicotine and ethanol resulted in an additive effect on the released DA. This additive effect was not observed with higher doses of nicotine and ethanol. Administration of the nicotinic antagonist mecamylamine into VTA completely blocked ethanol-induced DA release. CONCLUSIONS: These data support the hypothesis that the reinforcing effects of ethanol are at least partially mediated through the nicotinic receptors in the VTA. Furthermore, administration of selective nicotinic antagonists may be of therapeutic potential in reducing the rewarding effects of ethanol. The data also suggest that the combined effects of ethanol and nicotine on the "reward pathway" may be a contributing factor to the high incidence of smoking in alcoholics.     

Nicotine dependence

Nicotine is the principle alkaloid in tobacco and is considered to be responsible for tobacco dependence due to its psychoactive properties and its capacity to induce self-administration behavior in animals. Its action affects the brain where it binds to specific nicotinic receptors distributed on the mesolimbic and mesocortial dopaminergic pathways. Dopamine release by the nerve endings on these pathways provokes activation of the cerebral response. Acute stimulation with nicotine provokes a rise in cerebral dopamine levels in the accumbens. Dopamine release is greatly lowered in animals having undergone chronic exposure to nicotine, suggesting desensitization of the nicotinic receptors. In the regular smoker, there is an increase in the number of cerebral nicotinic receptors which would be a neuroadaptation response to desensitization. Reduction in the serum nicotine level favors resensitization of the nicotinic receptors and their vacuity would be the cause of the withdrawal syndrome. In therapeutics, nicotinic substitutes can effectively suppress the withdrawal syndrome and lead to abstinence rates to the order of 20 to 25% at one year. Psychotropes can also be effective to help patients stop smoking. Their mechanism of action is not clearly established but most would act by increasing the level of cerebral dopamine. They are used independently of their antidepressor effect with abstinence rates to the order of 25 to 30% at one year. Their combination with nicotinic substitutes can increase the rate of success.     

Striatal involvement in human alcoholism and alcohol consumption, and withdrawal in animal models

Background: Different regions of the striatum may have distinct roles in acute intoxication, alcohol seeking, dependence, and withdrawal. Methods: The recent advances are reviewed and discussed in our understanding of the role of the dorsolateral striatum (DLS), dorsomedial striatum (DMS), and ventral striatum in behavioral responses to alcohol, including alcohol craving in abstinent alcoholics, and alcohol consumption and withdrawal in rat, mouse, and nonhuman primate models. Results: Reduced neuronal activity as well as dysfunctional connectivity between the ventral striatum and the dorsolateral prefrontal cortex is associated with alcohol craving and impairment of new learning processes in abstinent alcoholics. Within the DLS of mice and nonhuman primates withdrawn from alcohol after chronic exposure, glutamatergic transmission in striatal projection neurons is increased, while GABAergic transmission is decreased. Glutamatergic transmission in DMS projection neurons is also increased in ethanol withdrawn rats. Ex vivo or in vivo ethanol exposure and withdrawal causes a long‐lasting increase in NR2B subunit‐containing NMDA receptor activity in the DMS, contributing to ethanol drinking. Analyses of neuronal activation associated with alcohol withdrawal and site‐directed lesions in mice implicate the rostroventral caudate putamen, a ventrolateral segment of the DMS, in genetically determined differences in risk for alcohol withdrawal involved in physical association of the multi‐PDZ domain protein, MPDZ, with 5‐HT_2C receptors and/or NR2B. Conclusions: Alterations of dopaminergic, glutamatergic, and GABAergic signaling within different regions of the striatum by alcohol is critical for alcohol craving, consumption, dependence, and withdrawal in humans and animal models.     

Action of Ethanol on Responses to Nicotine From Cerebellar Interneurons and Medial Septal Neurons: Relationship to Methyllycaconitine Inhibition of Nicotine Responses

BACKGROUND: A majority of alcoholics also smoke, suggesting that alcohol and nicotine share a common action on nicotinic cholinergic receptors. METHODS: Extracellular single-unit recording was used to investigate the effects of ethanol on responses to nicotine from rat cerebellar interneurons and medial septal neurons. RESULTS: Nicotine produced inhibition from medial septal neurons, but increased neural activity of cerebellar interneurons. When ethanol was applied locally to cerebellar interneurons, the excitatory response to nicotine was enhanced in a dose-related manner. Nicotine-induced inhibition from medial septal neurons was reduced by ethanol from the majority of neurons, but a dose relationship for this inhibition by ethanol was not observed. Ethanol affected responses to nicotine from over 90% of all neurons investigated at these sites. Initially, it was established that the nicotinic antagonists, methyllycaconitine (MLA) and alpha-bungarotoxin, which affect a nicotinic cholinergic (nACh) receptor with an alpha7 subunit, had similar actions on responses to nicotine from individual medial septal cells and cerebellar interneurons. When MLA was tested against responses to nicotine from neurons in the two brain regions, MLA antagonized responses to nicotine from only 27% of the neurons rather than the 90% found for ethanol. This latter observation provided evidence that ethanol was affecting neurons with MLA-insensitive receptors. When the actions of ethanol on responses to nicotine were compared directly with the action of MLA on the same medial septal neurons, both ethanol and MLA caused a greater than 50% antagonism of the response to nicotine, indicative that nACh receptors with the alpha7 subunit were sensitive to ethanol. CONCLUSIONS: Collectively, these data provide evidence that ethanol affects responses to nicotine not only from nACh receptors on medial septal cells and cerebellar interneurons containing an alpha7 subunit (i.e., MLA-sensitive receptors), but also from nACh receptor subtypes without this specific nACh receptor subunit (i.e., MLA-insensitive receptors).     

Adolescent vulnerabilities to chronic alcohol or nicotine exposure: findings from rodent models

This article presents an overview of the proceedings from a symposium entitled “Is adolescence special? Possible age‐related vulnerabilities to chronic alcohol or nicotine exposure,” organized by Susan Barron and Linda Spear and held at the 2004 Research Society on Alcoholism Meeting in Vancouver, British Columbia. This symposium, cosponsored by the Fetal Alcohol Syndrome Study Group and the Neurobehavioral Teratology Society, focused on our current knowledge regarding the long‐term consequences of ethanol and/or nicotine exposure during adolescence with the emphasis on data from rodent models. The support from these two societies represents the understanding by these research groups that adolescence represents a unique developmental stage for the effects of chronic drug exposure and also marks an age in which many risky behaviors including alcohol consumption and smoking typically begin. The speakers included (1) Aaron White, who presented data on the effects of adolescent ethanol exposure on subsequent motor or cognitive response to an ethanol challenge in adulthood; (2) Richard Bell, who presented data suggesting that genetic differences could play a role in adolescent vulnerability to ethanol; (3) Craig Slawecki, who presented data looking at the effects of chronic exposure to alcohol or nicotine on neurophysiologic and behavioral end points; and (4) Ed Levin, who presented data on acute and long‐term consequences of adolescent nicotine exposure. Finally, Linda Spear provided some summary points and recommendations regarding unresolved issues and future directions.     

Development of ethanol withdrawal-related sensitization and relapse drinking in mice selected for high- or low-ethanol preference

Background: Previous studies have shown that high alcohol consumption is associated with low withdrawal susceptibility, while at the same time, other studies have shown that exposure to ethanol vapor increases alcohol drinking in rats and mice. In the present studies, we sought to shed light on this seeming contradiction using mice selectively bred for High‐ (HAP) and Low‐ (LAP) Alcohol Preference, first, assessing these lines for differences in signs of ethanol withdrawal and second, for differences in the efficacy of intermittent alcohol vapor exposure on elevating subsequent ethanol intake. Methods: Experiment 1 examined whether these lines of mice differed in ethanol withdrawal‐induced CNS hyperexcitability and the development of sensitization to this effect following intermittent ethanol vapor exposure. Adult HAP and LAP lines (replicates 1 and 2), and the C3H/HeNcr inbred strain (included as a control genotype for comparison purposes) received intermittent exposure to ethanol vapor and were evaluated for ethanol withdrawal‐induced seizures assessed by scoring handling‐induced convulsions (HIC). Experiment 2 examined the influence of chronic intermittent ethanol exposure on voluntary ethanol drinking. Adult male and female HAP‐2 and LAP‐2 mice, along with male C57BL/6J (included as comparative controls) were trained to drink 10% ethanol using a limited access (2 h/d) 2‐bottle choice paradigm. After stable baseline daily intake was established, mice received chronic intermittent ethanol vapor exposure in inhalation chambers. Ethanol intake sessions resumed 72 hours after final ethanol (or air) exposure for 5 consecutive days. Results: Following chronic ethanol treatment, LAP mice exhibited overall greater withdrawal seizure activity compared with HAP mice. In Experiment 2, chronic ethanol exposure/withdrawal resulted in a significant increase in ethanol intake in male C57BL/6J, and modestly elevated intake in HAP‐2 male mice. Ethanol intake for male control mice did not change from baseline levels of intake. In contrast, HAP‐2 female and LAP‐2 mice of both sexes did not show changes in ethanol intake as a consequence of intermittent ethanol exposure. Conclusions: Overall, these results indicate that the magnitude of ethanol withdrawal‐related seizures is inversely related to inherited ethanol intake preference. Additionally, intermittent ethanol vapor exposure appears more likely to affect high‐drinking mice (C57BL/6J and HAP‐2) than low drinkers, although these animals are less affected by ethanol withdrawal.     

Activation of brain NOP receptors attenuates acute and protracted alcohol withdrawal symptoms in the rat

Background: Alcohol withdrawal refers to a cluster of symptoms that may occur from suddenly ceasing the use of alcohol after chronic or prolonged ingestion. These symptoms make alcohol abstinence difficult and increase the risk of relapse in recovering alcoholics. In previous studies, we demonstrated that treatment with Nociceptin/orphanin FQ (N/OFQ) significantly reduces alcohol consumption and attenuates alcohol‐seeking behavior induced by environmental conditioning factors or by stress in rats. In this study, we evaluated whether activation of brain NOP receptors may also attenuate alcohol withdrawal signs in rats. Methods: For this purpose, animals were subjected to a 6‐day chronic alcohol intoxication (by intragastric administration), and at 8, 10, and 12 hours following cessation of alcohol exposure, they were treated intracerebroventricularly (ICV) with N/OFQ (0.0, 1.0, and 3.0 μg/rat). Somatic withdrawal signs were scored after ICV treatment. In a subsequent experiment, to evaluate N/OFQ effects on alcohol withdrawal‐induced anxiety, another group of rats was subjected to ethanol intoxication and after 1 week was tested for anxiety behavior in the elevated plus maze (EPM). In the last experiment, an additional group of rats was tested for anxiety elicited by acute ethanol intoxication (hangover anxiety). For this purpose, animals received an acute dose (3.0 g/kg) of 20% alcohol and 12 hour later were tested in the EPM following ICV N/OFQ (0.0, 1.0, and 2.0 μg/rat). Results: Results showed that N/OFQ significantly reduced the expression of somatic withdrawal signs and reversed anxiety‐like behaviors associated with both chronic and acute alcohol intoxication. N/OFQ did not affect anxiety scores in nondependent animals. Conclusions: These findings suggest that the N/OFQ‐NOP receptor system may represent a promising target for the development of new treatments to ameliorate alcohol withdrawal symptoms.     

Chronic, but not acute, nicotine exposure attenuates ethanol withdrawal-induced hippocampal damage in vitro

BACKGROUND: Long-term ethanol use and long-term tobacco use frequently occur together, which suggests concurrent dependence on ethanol and nicotine. Consequences of this form of polydrug dependence are not well understood, however. Previous evidence suggests detrimental effects of long-term ethanol and beneficial effects of nicotine exposure on neuronal viability. Thus, the present study was designed to use an organotypic hippocampal slice culture model to examine the ability of chronic and acute nicotine exposure to reduce neurotoxicity associated with withdrawal from long-term ethanol exposure. METHODS AND RESULTS: Twenty-four hours of withdrawal after continuous 10 day ethanol exposure (50 or 100 mM in culture medium) resulted in cytotoxicity in hippocampal slice explants obtained from neonatal rat, most notably in pyramidal cell layers of the CA1 region. Exposure of slices to the N-methyl-D-aspartate receptor blocker MK-801 during ethanol withdrawal significantly reduced this toxicity. Exposure of slices to nicotine (0.1-10.0 microM) during the 24 hr withdrawal period did not reduce hippocampal damage. However, treatment of slices with nicotine (0.1-10.0 microM) during 10 days of ethanol exposure was associated with significant reductions in subsequent withdrawal-induced cytotoxicity, an effect reduced by mecamylamine coexposure with nicotine and ethanol. CONCLUSIONS: These findings indicate the development of marked hippocampal neurotoxicity during withdrawal from long-term ethanol exposure that is mediated, in part, by overactivation of N-methyl-D-aspartate receptors. Furthermore, these data suggest that one consequence of concurrent dependence on ethanol and nicotine may be reduced neurological damage associated with ethanol withdrawal.     

Increased ethanol self-administration and anxiety-like behavior during acute ethanol withdrawal and protracted abstinence: regulation by corticotropin-releasing factor

BACKGROUND: Animal models of alcohol dependence suggest that long-term alterations in brain corticotropin-releasing factor (CRF) systems, key mediators of the behavioral stress response, may be involved in the development and reinstatement of dependence on drugs of abuse. The objective of the present study was to investigate the role of CRF in the regulation of ethanol self-administration and to examine the behavioral stress response during acute withdrawal and protracted abstinence. METHODS: Male Wistar rats were made dependent on ethanol via chronic exposure to ethanol vapor. Ethanol self-administration and exploratory behavior in the elevated plus maze were measured at 2 hr and 3 to 5 weeks after exposure. The role of CRF in ethanol self-administration was examined via central injection of the CRF receptor antagonist D-Phe-CRF(12-41). RESULTS: Rats showed increased responding for ethanol 2 hr and 3 to 5 weeks after chronic ethanol exposure, which was attenuated by central injection of D-Phe-CRF(12-41). In addition, rats displayed a decrease in open-arm exploration in the elevated plus maze when tested 2 hr and 4 weeks after exposure. CONCLUSIONS: These results indicate that chronic ethanol exposure leads to increased ethanol self-administration and decreased open-arm exploration in the elevated plus maze during acute withdrawal and protracted abstinence. Attenuation of ethanol self-administration via central injection of D-Phe-CRF(12-41) implicates CRF as an underlying mechanism regulating long-term motivational effects associated with alcohol dependence.     

吸烟药理和戒烟步骤

吸烟成瘾主要是尼古丁成瘾,尼古丁成瘾主要与尼古丁增加多巴胺、去甲。肾上腺素和阿片肽释放相关联,所以烟瘾的治疗致力于用尼古丁替代治疗（如尼古丁肤贴）、尼古丁受体部分激动剂（如法伦克兰）和增加多巴胺和去甲肾上腺素和多巴胺能的药物（如安非他酮）。戒烟步骤是轻度可选心理咨询,中度可选单一药物治疗,重度则选联合药物治疗,联合药物治疗优选联合尼古丁替代治疗,难治者才选安非他酮联合尼占丁替代治疗。     

Effects of Chronic Alcohol on Immunoreactive β-Endorphin Secretion from Hypothalamic Neurons in Primary Cultures: Evidence for Alcohol Tolerance, Withdrawal, and Sensitization Responses

Endogenous opioid peptides are known to be involved in the alcohol tolerance and dependence following alcohol abuse. However, the cellular mechanisms involved in the ethanol tolerance and dependence are not well established. We have previously shown that low concentrations of ethanol stimulate immunoreactive β-endorphin (IR-β-EP) release from the cultured hypothalamic neurons and that chronic ethanol exposure desensitizes these neurons to ethanol challenges. In this study, we determined the IR-β-EP response to increasing doses of ethanol during the desensitizing phase of moderate ethanol doses to test whether the cultured IR-β-EP-secreting neurons develop tolerance to ethanol following constant exposure. We also determined IR-β-EP responses following withdrawal from chronic ethanol challenge and compared the IR-β-EP secretory response to various doses of ethanol in ethanol-naive and ethanol-preexposed cultures. The IR-β-EP responses to increasing doses of ethanol (50-150 mM) were markedly reduced in the cultures preexposed to a 50 mM dose of ethanol when compared with those that were naive to ethanol. The ethanol-exposed cultures showed hypersecretion of IR-β-EP after removal from 48 hr of constant ethanol, as compared with ethanol-naive cultures. When ethanol-preexposed cultures were challenged with various doses of ethanol 4 days after ethanol withdrawal, the cultures showed higher IR-β-EP secretory responses than did the ethanol-naive cultures. These data suggest that IR-β-EP secretory neurons in primary cultures develop tolerance to chronic ethanol, show withdrawal response after removal of chronic ethanol exposure, and develop sensitization following repeated ethanol challenges.     

Effects of lorazepam treatment for multiple ethanol withdrawals in mice

Background: Although many alcohol‐dependent patients present with a history of prior detoxifications, the efficacy and safety of pharmacotherapy in the context of multiple ethanol withdrawal experiences have not been extensively studied. The purpose of this study was to evaluate the ability of lorazepam treatment for multiple withdrawals to prevent or blunt the development/expression of sensitized central nervous system hyperexcitability during a subsequent untreated withdrawal episode. A mouse model of withdrawal sensitization involving repeated ethanol withdrawals was used. Methods: Adult male C3H/He mice were exposed to different patterns of chronic ethanol vapor in inhalation chambers. One group received four cycles of 16 hr of ethanol exposure separated by 8‐hr withdrawal periods, another group was tested after a single 16‐hr exposure period, and a final group served as ethanol‐naïve controls. These groups were further divided into lorazepam dosage (0.25–1.0 mg/kg) conditions. Lorazepam was administered 1 hr into each of the first three withdrawal cycles (or equivalent times); no drug injections were given during the final (fourth) withdrawal cycle. The ability of lorazepam treatment to alter development and expression of sensitized handling‐induced convulsions (HIC), as well as changes in pentylenetetrazol seizure threshold dosage during an untreated withdrawal episode, was examined. Separate animals were used to assess the effects of lorazepam treatment on blood ethanol clearance and plasma levels of the benzodiazepine during the test withdrawal cycle. Results: Lorazepam dose‐dependently reduced HIC activity during successive withdrawal cycles, and this resulted in attenuated expression of the sensitized HIC response during the acute phase of a subsequent untreated withdrawal episode. However, HIC activity was exacerbated at later time points during this final test withdrawal in mice that had received lorazepam treatment for earlier withdrawals. A similar pattern of results was obtained for changes in pentylenetetrazol seizure threshold dosage. These results do not seem to be due to pharmacokinetic factors, because peak blood ethanol levels, rate of ethanol elimination, and plasma levels of lorazepam did not significantly differ among groups during the final test withdrawal cycle. Conclusions: Blocking central nervous system hyperexcitability during repeated ethanol withdrawals with lorazepam effectively blunts the development and expression of sensitized seizure activity during the acute phase of a subsequent unmedicated withdrawal episode. At later time points, withdrawal‐related seizure activity was exacerbated, and this is possibly reflective of an interaction between protracted ethanol withdrawal and withdrawal from the benzodiazepine. The clinical implications of these findings suggest that repeated use of benzodiazepines for treatment of multiple ethanol withdrawals may have some initial beneficial effects, but such treatment may also place patients at increased risk of seizures at later time points.     

Polyamines contribute to ethanol withdrawal-induced neurotoxicity in rat hippocampal slice cultures through interactions with the NMDA receptor

Background: Several reports demonstrate that withdrawal from long‐term ethanol exposure is associated with significant central nervous system neurotoxicity, produced at least in part by increased activity of N‐methyl‐d‐aspartate receptors (NMDARs). Recent evidence suggests that elevations in the synthesis and release of the polyamines spermidine and spermine, which are known modulators of NMDARs, contribute to the increased activity of the receptor during ethanol withdrawal. Therefore, the goal of this investigation was to examine what role, if any, spermidine and spermine have in the generation of ethanol withdrawal‐induced neurotoxicity. Methods: Neurotoxicity (measured as fluorescence of the cell death indicator propidium iodide, PI), glutamate release (measured by high‐performance liquid chromatography analysis), and polyamine concentrations (by high‐performance liquid chromatography) were measured in rat hippocampal slice cultures undergoing withdrawal from chronic (10 day) ethanol exposure (100 mM). In addition, the effects of the polyamine synthesis inhibitor di‐fluoro‐methyl‐ornithine (DFMO, 0.1–100 nM) and NMDAR polyamine‐site antagonists ifenprodil, arcaine, and agmatine (1 nM‐100 μM) on ethanol withdrawal‐ and NMDA‐induced neurotoxicity were measured. Results: Ethanol withdrawal significantly increased glutamate release (peaking at 18 hr with a 53% increase), increased concentrations of putrescine and spermidine (136% and 139% increases, respectively, at 18 hr), and produced significant cytotoxicity in the CA1 hippocampal region (56% increase in PI staining relative to controls) of the cultures. The cell death produced by ethanol withdrawal was significantly inhibited by ifenprodil (IC₅₀= 14.9 nM), arcaine (IC₅₀= 37.9 nM), agmatine (IC₅₀= 41.5 nM), and DFMO (IC₅₀= 0.6 nM). NMDA (5 μM) significantly increased PI staining in the CA1 region of the hippocampal cultures (365% relative to controls), but ifenprodil, arcaine, agmatine, and DFMO all failed to significantly affect this type of toxicity. Conclusions: These data implicate a role for polyamines in ethanol withdrawal‐induced neurotoxicity and suggest that inhibiting the actions of polyamines on NMDARs may be neuroprotective under these conditions.     

Mechanisms of Alcohol-Nicotine Interactions: Alcoholics Versus Smokers

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Toshio Narahashi and Bo Söderpalm. The presentations were (1) Nicotinic mechanisms and ethanol reinforcement: Behavioral and neurochemical studies, by Bo Söderpalm, M. Ericson, P. Olausson, and J. A. Engel; (2) Chronic nicotine and ethanol: Differential regulation in gene expression of nicotinic acetylcholine receptor subunits, by X. Zhang and A. Nordberg; (3) Nicotine-ethanol interactions at neuronal nicotinic acetylcholine receptors, by Toshio Narahashi, William Marszalec, and Gary L. Aistrup; (4) Relapse prevention in alcoholics by cigarette smoking? Treatment outcome in an observational study with acamprosate, by L.G. Schmidt, U. Kalouti, M. Smolka, and M. Soyka; and (5) Effect of nicotine on voluntary ethanol intake and development of alcohol dependence in male rats, by L. Hedlund and G. Wahlström.     

The relationship between hippocampal acetylcholine release and cholinergic convulsant sensitivity in withdrawal seizure-prone and withdrawal seizure-resistant selected mouse lines

Background The septo‐hippocampal cholinergic pathway has been implicated in epileptogenesis, and genetic factors influence the response to cholinergic agents, but limited data are available on cholinergic involvement in alcohol withdrawal severity. Thus, the relationship between cholinergic activity and responsiveness and alcohol withdrawal was investigated in a genetic animal model of ethanol withdrawal severity. Methods Cholinergic convulsant sensitivity was examined in alcohol‐naïve Withdrawal Seizure—Prone (WSP) and—Resistant (WSR) mice. Animals were administered nicotine, carbachol, or neostigmine via timed tail vein infusion, and the latencies to onset of tremor and clonus were recorded and converted to threshold dose. We also used microdialysis to measure basal and potassium‐stimulated acetylcholine (ACh) release in the CA1 region of the hippocampus. Potassium was applied by reverse dialysis twice, separated by 75 min. Hippocampal ACh also was measured during testing for handling‐induced convulsions. Results Sensitivity to several convulsion endpoints induced by nicotine, carbachol, and neostigmine were significantly greater in WSR versus WSP mice. In microdialysis experiments, the lines did not differ in basal release of ACh, and 50 mM KCl increased ACh output in both lines of mice. However, the increase in release of ACh produced by the first application of KCl was 2‐fold higher in WSP versus WSR mice. When hippocampal ACh was measured during testing for handling‐induced convulsions, extracellular ACh was significantly elevated (192%) in WSP mice, but was nonsignificantly elevated (59%) in WSR mice. Conclusions These results suggest that differences in cholinergic activity and postsynaptic sensitivity to cholinergic convulsants may be associated with ethanol withdrawal severity and implicate cholinergic mechanisms in alcohol withdrawal. Specifically, WSP mice may have lower sensitivity to cholinergic convulsants compared with WSR because of postsynaptic receptor desensitization brought on by higher activity of cholinergic neurons.     

Nicotine stimulation on extracellular glutamate levels in the nucleus accumbens of ethanol-withdrawn rats in vivo

Background: Nicotine can release glutamate in the limbic system. Presynaptic activation of glutamate receptors might be relevant for the subsequent firing of excitatory postsynaptic potentials. This might be relevant in early ethanol withdrawal. The effects and differences of nicotine stimulation on glutamate response measured by microdialysis in the nucleus accumbens (NAC) between ethanol‐withdrawn rats (EW group) and ethanol‐naïve rats (control group) were investigated. Methods: Rats were ethanol‐intoxicated according to a binge‐drinking model: recurrent cycle of 4 days of intoxication (EW group) or 5% sucrose (control group), followed by a 3‐day recovery. This was followed by a 2‐day intoxication period and subsequent abstinence. After the last oral intake, microdialysis was performed in the left NAC for a 16‐hour withdrawal period. At the end of the withdrawal period, a rated withdrawal score (RWS) was documented. Then, nicotine was given subcutaneously at a dose of 0.5 mg/kg and amino acid levels determined by microdialysis were followed for an additional 3 hours. Results: The RWS was not correlated to the last amount of ethanol received, but was correlated to the total amount of ethanol administered during the pretreatment period: the basal values of extracellular glutamate were found to be decreased in the EW group before withdrawal. Cessation of ethanol significantly increased glutamate levels with a peak between 4 and 10 hours after the last oral intake. Sixteen hours after ethanol withdrawal, the same level as in the control group was achieved. Nicotine significantly increased glutamate levels in the NAC of the EW group but not in ethanol‐naïve rats. Conclusions: This study showed that withdrawal of ethanol was associated with an increase in extracellular glutamate levels. Systemic administration of nicotine in vivo produced an increase in extracellular levels of glutamate in the core region of the NAC during ethanol withdrawal. This might be a relevant pathomechanism for increased craving either for alcohol or for nicotine after ethanol withdrawal.     

Modulation of F-met-leu-phe Induced Chemotactic Activity and Superoxide Production by Neutrophils during Chronic Ethanol Intoxication

Chronic alcohol consumption has been associated with increased migration of neutrophils into liver that could contribute to the development of alcoholic liver disease. Mild endotoxemia may be at least partially responsible for this condition since endotoxemia was shown to be present in virtually all chronic alcoholics. This study examines the release of superoxide anion and chemotactic activity by Kupffer cells and sequestered hepatic as well as blood neutrophils during chronic alcohol intoxication (16 weeks) alone, and following an intravenous injection of Escherichia coli lipopolysaccharide (LPS) (1 mg/kg) 3 hr before cell isolation. Chronic ethanol consumption increased the total neutrophil yield per liver, but did not change the f-met-leu-phe induced chemotactic activity by both hepatic and blood neutrophils. However, the combined insults of ethanol and LPS increased the chemotactic activity and superoxide anion generation by these cells. Plasma from ethanol-fed rats was highly chemotactic to syngeneic normal rat neutrophils. This activity was increased 1.75-fold in the plasma obtained from chronic ethanol plus endotoxin-injected rats. The chemotactic activity of Kupffer cells was not significantly modulated during ethanol intoxication plus endotoxin treatment. The f-met-leu-phe-induced superoxide anion release by Kupffer cells was enhanced after LPS treatment. Chronic ethanol consumption did not induce any effect on this parameter. These observations suggest that functional alterations in neutrophils during chronic ethanol intoxication may contribute to hepatic injury.     

Abrupt Termination of an Ethanol Regimen Provokes Ventricular Arrhythmia and Enhances Susceptibility to the Arrhythmogenic Effects of Epinephrine in Rats

Background: Pathologists examining victims of sudden unexpected death encounter alcoholics more often than expected; alcohol may play a role in sudden arrhythmic death. Here we determine whether a pattern of alcohol consumption, chronic ethanol intake, and withdrawal increases the incidence of malignant ventricular arrhythmia and modulates susceptibility to the arrhythmogenic potential of sympathetic stimulation from an epinephrine test in rats. Methods: Male Wistar rats were treated with a continuous ethanol liquid diet for 7 weeks, and then subjected to 1-day withdrawal or 21-day abstinence. Ventricular ectopy was evaluated by 24-hour electrocardiographic telemetry recording; whole-body sympathetic activation, cardiac sympathovagal balance, and susceptibility to ventricular arrhythmia induced by sympathetic stimulation were evaluated based on blood noradrenalin metabolite concentrations, heart rate variability, and a 3-step epinephrine test. Results: Ventricular arrhythmia and related death were observed only in rats at 1 day of withdrawal, but not in nonalcoholic, continuous ethanol intake or 21-day abstinence rats. One-day withdrawal after a 7-week continuous ethanol regimen elevated circulating noradrenalin metabolite levels and induced cardiac sympathovagal imbalance. Deaths related to the epinephrine test and ventricular arrhythmia induced by low doses of epinephrine were observed only in 1-day withdrawal rats. However, all anomalies were normalized by 21-day abstinence. Conclusions: Abrupt termination of a 7-week continuous ethanol regimen is sufficient to enhance the whole-body sympathetic activation and cardiac sympathovagal imbalance that contribute to ventricular arrhythmia and sudden death in alcoholic rats. Those providing medical care for alcoholics, including in cases of legal imprisonment, should be aware of the possibility of enhanced susceptibility to sudden arrhythmic death due to the abrupt termination of a chronic ethanol regimen.     

Increased Anxiety-Like Behavior and Ethanol Self-Administration in Dependent Rats: Reversal via Corticotropin-Releasing Factor-2 Receptor Activation

BACKGROUND: Corticotropin-releasing factor (CRF) has been hypothesized to be one of the main regulators of the stress response observed during alcohol withdrawal. The CRF receptor subtypes seem to have a differential role in the regulation of stress-related behavior. Given the behavioral characterization of these receptors, the objective of the following experiments was to characterize the role of CRF2 receptors in the interaction between alcohol and stress by examining the effects of CRF2 receptor activation in the behavioral stress response and ethanol self-administration during early ethanol withdrawal in dependent rats. METHODS: Male Wistar rats were made dependent on ethanol via chronic exposure to an ethanol containing liquid diet. Behavior in the elevated plus maze and ethanol self-administration were measured at 2 hr after removal of the diet. The role of the CRF2 receptor in the regulation of these behaviors during the early stages of withdrawal was examined via central injection of the highly selective CRF2 receptor agonist urocortin 3. RESULTS: Rats showed decreased exploration of the open arms of the elevated plus maze, an indication of a heightened behavioral stress response, after chronic ethanol exposure. This effect was attenuated by central injection of urocortin 3. In addition, urocortin 3 injections reversed the increase in ethanol self-administration observed during early withdrawal in dependent rats. CONCLUSIONS: Reversal of the increased stress-related behavior in the elevated plus maze observed after injections of urocortin 3 indicates that the decreased responding for ethanol also seen after urocortin 3 administration is likely due to a diminished anxiety-like state. These data suggest that activation of the CRF2 receptor may provide a novel target in the attenuation of the stress response characteristic of the early stages of ethanol withdrawal.     

Disruptions in sleep time and sleep architecture in a mouse model of repeated ethanol withdrawal

BACKGROUND: Insomnia and other sleep difficulties are perhaps the most common and enduring symptoms reported by alcoholics undergoing detoxification, especially those alcoholics with a history of multiple detoxifications. While some studies have reported sleep disruptions in animal models after chronic ethanol exposure, the reports are inconsistent and few address sleep architecture across repeated ethanol exposures and withdrawals. The present study evaluated sleep time and architecture in a well-characterized mouse model of repeated chronic ethanol exposure and withdrawal. METHODS: C57BL6/J mice were fitted with electrodes in frontal cortex, hippocampus, and nuchal muscle for collection of continuous electroencephalogram (EEG)/electromyogram (EMG) data. Baseline data were collected, after which mice received 4 cycles of 16-hour exposure to alcohol (ethanol: EtOH) vapor separated by 8-hour periods of withdrawal or similar handling in the absence of EtOH vapor. Ethanol-exposed mice attained a blood ethanol concentration of 165 mg%. Upon completion of vapor exposure, EEG/EMG data were again collected across 4 days of acute withdrawal. Data were subjected to automated analyses classifying 10-second epochs into wake, non-rapid eye movement (REM) sleep, or REM sleep states. RESULTS: Mice in withdrawal after chronic EtOH exposure showed profound disruptions in the total time asleep, across the acute withdrawal period. Sleep architecture, the composition of sleep, was also disrupted with a reduction in non-REM sleep concomitant with a profound increase in REM sleep. While altered sleep time and non-REM sleep loss resolved by the fourth day of withdrawal, the increase in REM sleep ("REM rebound") persisted. CONCLUSIONS: These results mirror those reported for the human alcoholic and demonstrate that EtOH withdrawal-induced sleep disruptions are evident in this mouse model of alcohol withdrawal-induced sensitization. This mouse model may provide mechanisms to investigate fully the high correlation between unremitting sleep problems and increased risk of relapse documented clinically.