Rate-Depressant Effects of Ethanol on Fixed-Ratio Responding in ALKO AA and ANA Rats

The ALKO AA and ANA rats have been selectively bred for high versus low ethanol preference, respectively. AA rats have been shown to self-administer ethanol, whereas ANA rats do not. These animals also show a range of differences on tasks which measure sensitivity to ethanol, but the relationship between ethanol intake and sensitivity to this drug in these rats is not clear. This study examined sensitivity to ethanol in AA and ANA rats as determined by ethanol's rate depressant effects on schedule controlled (Fixed-Ratio (FR) 32) responding reinforced by water deliveries. Non-drug rates of responding were similar for both lines across baseline, sham injection and vehicle conditions. Ethanol produced dose-dependent decreases in responding in both the AA and ANA rats. Dose-response curves indicated that AA rats were slightly more sensitive to the acture effects of ethanol than were ANA rats, with ED50 values of 0.52 and 0.69 g/kg for AA and ANA rats, respectively. Overall, however, the effects of ethanol on rats of responding were similar across the two lines of rats. While it is possible that constraints on behavior imposed by FR schedules could be masking underlying differences in tissue sensitivity between these animals, the results indicate that ethanol intake under preference or reinforceemnt conditions does not appear to be highly controlled by initial sensitivity to ethanol as measured by effects on operant performance.     

Consumption of intoxicating beverages by rats and mice exhibiting high and low preferences for ethanol

Lines of rats selectively bred for alcohol consumption or avoidance (AA and ANA, ALKO, Finland) as well as inbred strains of mice (C57/BL/6J and DBA/2J) and common female Wistar rats (Charles River) exhibiting high and low preferences for ethanol were tested under free-choice conditions for their consumption of solutions of ethanol (5, 10, or 15 g/100 ml tap water), sodium pentobarbital (0.19, 0.038, 0.076 g/100 ml tap water), and different beverages containing ethanol in the range of 8.1–9.6% (red and white wine, Scotch, ethanol in Hawaiian Punch). The Wistar rats and the mice classified as alcohol-preferring also tended to consume more of the pentobarbital solution than did alcohol-avoiding animals. Alcohol-nonaccepting (ANA) rats, however, consumed considerably more of all three pentobarbital solutions than did the alcohol-accepting (AA) rats. The intake of pentobarbital by the ANA rats and C57/BL/6J mice was in the range of 25–40 mg/kg/day, quantities that might be expected to produce pharmacological effects discriminable by those animals. The intake of ethanol by ANA rats was markedly elevated when the ethanol was contained in white wine or in punch.     

Renin,Water drinking,salt preference and blood pressure in alcohol preferring and alcohol avoiding rats

Mechanisms controlling fluid volume were studied in alcohol preferring AA (Alko, Alcohol) and alcohol avoiding ANA (Alko, Non-Alcohol) rats. Hypertonic sodium chloride solution (5%) given orally caused a higher dipsogenic response in AA rats than in the ANA's. One hour after ethanol loading (4.8 g/kg, by stomach tube), plasma renin activity of AA rats was four times as high as in ANA rats. ANA rats had higher degree of sodium chloride (0.9%) preference and higher blood pressure. The strain differences in voluntary salt intake and salt metabolism may modulate the consumption of calories and water as well as blood pressure and different reactivity of the renin system in AA and ANA rats.     

Intravenous heroin and ethanol self-administration by alcohol-preferring AA and alcohol-avoiding ANA rats

The alcohol-preferring AA rats have previously been shown to drink more solution containing the opioid etonitazene than the alcohol-avoiding ANA rats. The present experiments were initiated to see whether the line difference in opioid and alcohol intake would persist if an intravenous (IV) route of self-administration is used. Following establishment of stable heroin responding (0.03 mg/kg per infusion), AA and ANA rats were first subjected to three within-session dose-response determinations during which they were allowed to respond for ascending heroin doses (0.0075, 0.015, 0.03, and 0.06 mg/kg per infusion) and then to one progressive-ratio schedule session. AA rats obtained more heroin infusions than ANAs during the first acquisition sessions but there were no significant differences between the lines either in their baseline heroin responding, across the ascending within-session doses, or on the progressive ratio probe. When, after additional heroin baseline sessions, ethanol (1.0 mg/kg per infusion) was substituted for heroin, AA rats initially increased their responding and showed stable rates for responding across ascending ethanol doses (2.0 and 4.0 mg/kg), whereas ANAs declined below their heroin baseline. These findings give evidence for only an initial line difference in IV opiate self-administration but for a sustained difference in IV ethanol self-administration, thus suggesting that the differential alcohol drinking of the AA and ANA rats is dependent at least partly on non-oral factors.     

Genetic differences in the establishment of ethanol as a reinforcer

Ethanol, self-administered orally, has been shown to serve as an effective reinforcer in several species. Self-administration studies have also illustrated that ethanol-drinking behavior can be conceptualized as a specific type of operant behavior. The use of inbred and selectively bred animals in other areas of alcohol research has provided valuable information about the contribution of genetic factors to ethanol-related behaviors. Our research was designed to study genetic differences in oral self-administration in the ALKO AA (Alcohol Accepting) and ANA (Alcohol Non-Accepting) rat lines, selected for ethanol preference. Thus, we applied a behavior genetic analysis to aid in determining the contribution of genetic factors to behavior, specifically drug-seeking behavior. The results of our experiments indicate that genetic differences are important factors contributing to the establishment of a drug as a reinforcer. At least in the case of ethanol, the drug did not act as a reinforcer in non-preferring animals. Conversely, in preferring animals, ethanol was readily established as a reinforcer.     

Nicotine in alcohol deprivation increases alcohol operant self-administration during reinstatement

Tobacco and alcohol are highly co-abused by humans. Most experimental studies have evaluated ethanol consumption in animals exposed concomitantly to nicotine. However, little is known regarding the effects of nicotine administered during periods of alcohol deprivation. In the present study, adult male Wistar rats with an extended background of operant self-administration of ethanol were alcohol-deprived and treated with nicotine (0.1, 0.2, 0.4 and 0.8 mg/kg) or saline during five consecutive days in one chamber of a place conditioning apparatus. Nicotine-induced changes in locomotion were monitored daily, whereas the expression of place conditioning was studied the day after the last nicotine injection. Forty-eight hours after testing for conditioning, the animals resumed operant self-administration of ethanol and their alcohol intake was evaluated during the next 14 days. We observed that alcohol consumption was increased in animals treated with nicotine at doses of 0.2, 0.4 and 0.8 mg/kg but not in animals treated with the dose of 0.1 mg/kg or saline. Additionally, the dose of 0.8 mg/kg of nicotine not only induced persistent changes in alcohol self-administration but also produced conditioned place aversion and depressed locomotor activity. These results indicate that nicotine administration during the ethanol deprivation period can exacerbate the maintenance of alcohol consumption.     

Hepatic carbohydrate metabolism in rats bred for alcohol preference

The influence of ethanol on the carbohydrate metabolism was studied in two strains of rats: the AA strain with an inherited preference for alcohol and the ANA strain with an aversion to alcohol. In both strains, a single intraperitoneal dose of ethanol (1.5 g/kg body wt.) slightly increased the blood glucose concentration. In AA rats alcohol increased the rate of gluconeogenesis from alanine and had no effect on the liver glycogen stores, whereas in ANA rats the rate of gluconeogenesis remained unchanged and the glycogen stores decreased. It thus appears that the two rat strains maintain their blood glucose concentration by different mechanisms; the ANA rats utilise both glycogenolysis and gluconeogenesis but the AA rats only gluconeogenesis.     

先天性嗜酒大鼠的饮酒行为特性

目的系统考察先天性嗜酒(FH/Wjd)大鼠嗜酒的行为特性。方法采用双瓶(5%或10%乙醇和自来水)自由选择的方法,观察FH/Wjd大鼠的饮酒量、饮水量和乙醇偏爱率,并进一步探讨FH/Wjd大鼠饮酒的昼夜差异性;在乙醇剥夺实验中,研究乙醇剥夺24h对FH/Wjd大鼠饮酒量和乙醇偏爱率的影响;选用固定比率(FR1)实验程序,探讨FH/Wjd大鼠操作性自身饮酒的行为特点。结果在双瓶自由选择饮酒实验中,给予5%乙醇,大鼠的饮酒量为(4.3±0.2)g·kg-1·d-1,饮水量为(20.1±2.3)g·kg-1·d-1,乙醇偏爱率为(82.9±2.0)%;给予10%乙醇,大鼠的饮酒量为(6.4±0.2)g·kg-1·d-1,饮水量为(37.2±2.7)g·kg-1·d-1,乙醇偏爱率为(69.2±2.0)%,与5%乙醇相比较,饮酒量和饮水量显著增大,但乙醇偏爱率明显降低。FH/Wjd大鼠的饮酒行为呈明显的昼夜节律,夜间饮酒量和乙醇偏爱率均显著高于白天,夜间饮水量虽呈增加趋势,但差异无显著性。FH/Wjd大鼠乙醇剥夺24h,再次给酒后1h的饮酒量增加37.7%,乙醇偏爱率增加22.1%;再次给酒后24h的饮酒量增加15.6%,乙醇偏爱率存在增高趋势,但差异无显著性。FH/Wjd大鼠操作性自身饮酒行为训练13d后,连续测试3d,操作性饮酒行为的偏爱率为49%～64%。结论FH/Wjd大鼠具有饮酒量大和乙醇偏爱率高的特点,存在明显的乙醇剥夺效应,并可在短期内建立操作性自身饮酒行为,是一种理想的先天嗜酒动物模型。     

Oral ethanol reinforced behavior in inbred mice

The use of genetically defined animals in many areas of alcohol research provides valuable information about the contribution of genetic factors to ethanol-related behaviors. Utilizing the principles of operant conditioning, we determined whether mice which are known for high ethanol preference, C57BL/6J males, would orally self-administer this substance. Strategies used with other species were successful in inducing pharmacologically significant blood alcohol levels and in establishing ethanol as a reinforcer in this mouse strain. Responding for and consumption of 8% (w/v) ethanol exceeded baseline levels of responding for water. This species and method may prove useful in determining the genetic relationship among various ethanol-related behaviors and their mechanisms of action and in studies of behavior reinforced by drugs.     

Intoxicating effects of three aliphatic alcohols and barbital on two rat strains genetically selected for their ethanol intake

Intoxicating effects of ethanol, isopropanol, tert. butanol and barbital were studied by comparing performances on the tilted plane of ethanol preferring AA (Alko, Alcohol) and ethanol avoiding ANA (Alko, Non-Alcohol) rat strains raised by genetic selection for their voluntary ethanol intake. The motor coordination of AA rats was found to be less affected than that of ANA rats by all three alcohols and barbital. The results indicate a marked genetic difference in neural tolerance to the alcohols and barbital, and suggest that neural tolerance to alcohols plays a role in determining the ethanol preference of AA rats and ethanol aversion of ANA rats.     

Alcohol-preferring AA rats show a derangement in their central melanocortin signalling system

The AA (Alko, Alcohol) rats are selectively bred for their preference of alcohol to water, contrasting to ANA rats that avoid alcohol. They also exhibit a lower growth rate compared to ANA rats, as well as differences in their response to substances affecting food intake. The melanocortin (MC) system is involved in the regulation of feeding behaviour and in mechanisms underlying drug addiction and tolerance. Recently, administration of an MC receptor agonist proved to reduce alcohol intake in AA rats. We predicted that the ratio of endogenous MC receptor agonists (proopiomelanocortin, POMC) and antagonists (agouti-related protein, AgRP) would differ from ANA rats, and that subsequent differences in MC receptor levels would be detectable. We used in situ hybridization to detect an increased ratio of POMC/AgRP mRNA in the arcuate nucleus (Arc) of AA rats. Receptor autoradiography indicated that MC3 receptor binding differed in the nucleus accumbens and several hypothalamic nuclei, possibly reflecting differences in MC peptide transmission in the AA rats. Our results support the claim that AA rats have a high ratio of POMC/AgRP expression, and that this observation is accompanied by differences in MC3 receptor levels.     

Effects of subunit selective nACh receptors on operant ethanol self-administration and relapse-like ethanol-drinking behavior

Rationale and objectives  The sensitivity to ethanol central effects is partially determined by the subunit composition of brain nicotinic acetylcholine receptors (nAChRs). Thus, the effects of intraventral tegmental area (VTA) administration of the nicotinic subunit-specific antagonist, α-conotoxin MII (αCtxMII, α₃β₂*, β₃*, α₆*), were compared to those of systemic mecamylamine (MEC, an allosteric negative modulator of the nAChR), dihydro-β-erythroidine (DHβE, α₄β₂*), and methyllycaconitine (MLA, α₇*) to elucidate involvement of different subunits of nAChRs in operant ethanol self-administration and relapse-like activation of ethanol consumption after ethanol deprivation in rats. Methods  The effects of drugs were studied in rats trained for operant oral self-administration of ethanol (FR = 1). For ethanol deprivation, trained animals were subjected to a period of alcohol deprivation for 10 days. αCtxMII was given directly into the VTA through implanted permanent intracranial cannulae, whereas MEC, DHβE, and MLA were administered systemically. Results  αCtxMII reduced operant ethanol self-administration and blocked the deprivation-induced relapse-like ethanol consumption. MEC reduced operant ethanol self-administration and inhibited the deprivation-induced increase in alcohol consumption. DHβE did not alter ethanol self-administration in the lower-dose range but inhibited ethanol intake at a higher dose (4 mg/kg), although this effect might have been nonspecific. MLA failed to block self-administration of ethanol and relapse-like drinking after deprivation. Conclusions  Our results indicate that nAChRs are involved in the modulation of operant alcohol self-administration and relapse-like alcohol drinking behavior in rats. Our observations support the working hypothesis that systemically active selective ligands for nAChR α₃β₂*, β₃, and/or α₆* receptor subunits might be of therapeutic value for the treatment of alcoholism.     

Genetic impairment of frontocortical endocannabinoid degradation and high alcohol preference.

Endocannabinoid signaling has recently been implicated in ethanol-seeking behavior. We analyzed the expression of endocannabinoid-related genes in key brain regions of reward and dependence, and compared them between the alcohol-preferring AA (Alko Alcohol) and nonpreferring ANA (Alko Non-Alcohol) rat lines. A decreased expression of fatty acid amidohydrolase (FAAH), the main endocannabinoid-degrading enzyme, was found in prefrontal cortex (PFC) of AA rats, and was accompanied by decreased enzyme activity in this region. Binding of the endocannabinoid-cannabinoid 1 (CB1) receptor ligand (3)[H]SR141716A, and [35S]GTPgammaS incorporation stimulated by the CB1 agonist WIN 55,212-2 were downregulated in the same area. Together, this suggests an overactive endocannabinoid transmission in the PFC of AA animals, and a compensatory downregulation of CB1 signaling. The functional role of impaired FAAH function for alcohol self-administration was validated in two independent ways. The CB1 antagonist SR141716A potently and dose-dependently suppressed self-administration in AA rats when given systemically, or locally into the PFC, but not in the striatum. Conversely, intra-PFC injections of the competitive FAAH inhibitor URB597 increased ethanol self-administration in nonselected Wistar rats. These results show for the first time that impaired FAAH function may confer a phenotype of high voluntary alcohol intake, and point to a FAAH both as a potential susceptibility factor and a therapeutic target.     

精神活性物质成瘾的行为医学研究

本课题建立吗啡,甲基苯丙胺以及可卡因诱导的大、小鼠行为敏化模型。探讨了L-型钙通道阻滞剂,情绪稳定剂(锂盐,丙戊酸钠和卡马西平),以及新型μ受体部分激动剂噻吩诺啡对行为敏化形成,转化以及表达的影响。利用行为敏化模型,率先开展了曲马朵和槟榔嚼块提取物多药滥用的精神药理学研究。此外,在条件性位置偏爱和纳洛酮促吗啡戒断动物模型上,发现钙调蛋白抑制剂具有明显的干预作用,钙调蛋白可能是阿片类物质依赖治疗的新的分子靶点。与澳大利亚成瘾神经科学的合作研究发现,GABAB受体正性别构调节剂CGP9730可以抑制嗜酒大鼠的自饮酒行为,具有潜在的治疗酒精依赖与成瘾的临床应用价值。     

Dopamine D3 receptor knockout mice and the motivational effects of ethanol

Dopamine D3 receptors have been implicated in the behavioral effects of abused drugs including ethanol. The present experiments characterized the acquisition of ethanol-induced place conditioning and ethanol self-administration in D3 knockout (D3 KO) mice compared with C57BL/6J (C57) mice. For place conditioning, D3 KO and C57 mice received six pairings of a tactile stimulus with ethanol (3 g/kg i.p.). D3 KO mice showed higher basal locomotor activity levels in comparison with the C57 mice during conditioning. Ethanol produced similar magnitudes of conditioned place preference in both genotypes. In a two-bottle drinking procedure, mice of each genotype received 24 h access to water and either 3% or 10% v/v ethanol. No difference was noted between D3 KO and C57 mice in either consumption or preference. In an operant self-administration procedure using 23 h sessions, D3 KO and C57 mice received access to 10% v/v ethanol on an FR4 schedule of reinforcement, food on an FR1 schedule of reinforcement and water from a sipper tube. D3 KO and C57 mice had similar response rates of ethanol and food as well as similar water intakes. Overall, these results indicate that elimination of D3 receptor function has little influence on ethanol reward or intake.     

Fluoxetine, Desipramine, and the Dual Antidepressant Milnacipran Reduce Alcohol Self-Administration and/or Relapse in Dependent Rats

A few clinical studies have shown that dual antidepressants (serotonergic (5-HT) and noradrenergic (NE) transporter inhibitors, SNRIs) may be effective in alcoholism treatment. We studied the effect of the dual antidepressant milnacipran on ethanol operant self-administration in acutely withdrawn ethanol-dependent and in -non-dependent Wistar rats, and used fluoxetine and desipramine to dissect both 5-HT and NE components, respectively, in the effect of milnacipran. Milnacipran was also tested for relapse after protracted abstinence and on ethanol-induced (1.0 g/kg) conditioned place preference in control rats and ethanol-induced locomotor sensitization in DBA/2J female mice. Milnacipran dose dependently (5–40 mg/kg) attenuated the increased ethanol self-administration observed during early withdrawal and was more potent in preventing reinstatement in dependent rats after protracted abstinence as compared with non-dependent rats. Desipramine and fluoxetine (10 mg/kg) blocked ethanol self-administration during early withdrawal, and recovery was delayed in dependent animals, indicating a potent effect. Ethanol self-administration was also reduced 1 day after treatment with desipramine and fluoxetine but not with milnacipran. Finally, milnacipran prevented ethanol-induced place preference in ethanol-naive rats and reduced the magnitude of ethanol-induced sensitization associated with a delayed induction in mice. Desipramine (20 mg/kg) countered sensitization development and reduced its expression at 1 week after treatment; fluoxetine (10 mg/kg) reduced sensitization expression. Thus, 5-HT and NE transmissions during sensitization expression may mediate the effect of milnacipran on sensitization induction. These results support that SNRIs may have a potential use in alcoholism treatment.     

Effects of oral ethanol self-administration on the inhibition of the lever-press response in rats.

The effects of ethanol on the inhibition of a learned response were examined in adult, male Wistar rats from two treatment groups: oral self-administration of alcoholic solution (10% ethanol and 10% glucose in distilled water) and oral self-administration of sweet solution (10% glucose in distilled water). Subjects were food deprived and alcoholic or control solutions were available 1 h per day during 15 days. After this period, rats were tested in a two-bottle paradigm during 1 h per day and placed in the operant chambers immediately afterward. This phase went on for 19 days. Subjects were trained to lever press for food and were tested in a continuous reinforcement schedule, operant extinction, successive discrimination, and two-stimuli tests. Alcohol impaired the ability to inhibit previously reinforced responses but only in situations indicated by exteroceptive stimuli. Ethanol intake did not impair the lever-press behavior neither in the acquisition of the response nor in the continuous reinforcement schedule. These data suggest that the sedative effects of alcohol at this dose were not apparent in reinforcement situations, in contrast with extinction situations.     

Ethanol and acetaldehyde metabolism in rat strains genetically selected for their ethanol preference

A study was made of ethanol and acetaldehyde metabolism in both sexes in rat strains genetically selected for their ethanol preference. The strains are denoted by ANA (Alko, Non-Alcohol), which prefers water to a 10% (v/v) ethanol solution, and AA (Alko, Alcohol), which prefers the ethanol solution. Peripheral blood and freeze-stopped livers were used for the in vivo studies. A once-through perfusion technique was applied so that in the same liver ethanol and acetaldehyde oxidation, the cytoplasmic redox state and oxygen consumption could be measured. In the female rats of the AA strain there was a higher rate of ethanol oxidation and oxygen consumption, compared with those of the ANA strain. A greater difference was found between the sexes, the female rats of both strains having a more rapid ethanol oxidation and oxygen consumption, compared with the respective males. The AA strain displayed a significantly lower level of acetaldehyde during ethanol oxidation than did the ANA strain. On comparison of the liver acetaldehyde concentrations with the mitochondrial NADH/NAD⁺ ratio, calculated from the 3-hydroxybutyrate/acetoacetate ratio, strain correlations were observed in both sexes, the ANA strain, with higher acetaldehyde, having a lower 3-hydroxybutyrate/acetoacetate ratio than the AA strain, with lower acetaldehyde. The results are discussed in relation to the regulation of the ethanol and acetaldehyde metabolism. The biochemical basis for ethanol preference is briefly discussed.     

Reduced alcohol drinking in adult rats exposed to sucrose during adolescence

Intake of sweet-alcoholic drinks during adolescence is believed to favor alcohol abuse and dependence in adulthood. This study examined the influence of early exposure to ethanol with or without sucrose on the consumption of sweet or alcoholic solutions in adulthood. Adolescent rats (from post-natal day 30-46) were given continuous free access to tap water and either 5% sucrose, 5% ethanol or mixed 5% sucrose-5% ethanol. The control group was given access to water only. Upon reaching adulthood (post-natal day 60), rats were tested for saccharin (sweet), quinine (bitter) and ethanol consumption using a two-bottle free-choice paradigm. The results indicated that pre-exposure to ethanol did not alter the intake of sweet or ethanol solutions in adulthood. However, rats exposed to sucrose during adolescence showed a decreased consumption of both sweet and ethanol solutions. Because alcohol has a sweet taste component, an additional group of rats, pre-exposed to either 5% sucrose or water during adolescence, was tested for intravenous ethanol self-administration (preventing oral sensory stimulation) and in a new model of simultaneous access to oral saccharin and intravenous ethanol that results in higher total ethanol intake. Relative to controls, sucrose-exposed rats showed reduced operant self-administration of saccharin, yet no differences were found for intravenous ethanol self-administration. Altogether, these findings indicate that sucrose exposure during adolescence persistently affected the perception of sweet taste reward and thereby alcohol’s acceptance in adulthood.     

Anxiety: a potential predictor of vulnerability to the initiation of ethanol self-administration in rats

Anxiolytic effects of ethanol have been proposed to be important factors in the initiation of ethanol consumption. To examine this hypothesis, drug-naive Wistar rats were tested in the elevated plusmaze to determine their initial level of anxiety. Based on their response, we separated the animals into anxious and non-anxious groups. After that, animals went through an oral ethanol self-administration procedure. Rats that were initially classified as anxious showed a significantly (P<0.01) higher intake and preference for ethanol during the initiation phase of the voluntary drinking procedure than non-anxious animals. In another experiment, intraperitoneal (IP) injections of ethanol (0.5–1.5 g/kg) produced dose-dependent anxiolytic effects in rats when tested in the elevated plus-maze procedure. Blood ethanol levels following IP injections during the plus-maze test were similar to those reached during the oral ethanol self-administration procedure, which shows that the rats indeed drank sufficient amounts of ethanol to experience its anxiolytic effects. These findings indicate that the basal level of anxiety plays an important role in vulnerability to alcohol drinking.