THE EFFECT OF WEEKLY EXPOSURES ON THE VOLUNTARY INTAKE OF ETHANOL IN INDIVIDUAL RATS

No pattern of ethanol exposure is at present known as a certainway to induce voluntary drinking of the drug in experimentalanimals. Based on an assurnptlon that humans who will ultimatelydevelop alcoholism do not start by drinking ethanol continuously,a chronic experiment was designed, where ethanol 2 g/kg intraperitoneally(i.p.) was injected in male rats once a week. Voluntary intakeof ethanol was tested in a two-bottle choice situation eitheron one day every week (restricted test) or continuously (continuoustest). During the first part of the intermittent treatment withethanol i.p., an inhibition of voluntary drinking in the restrictedtest was revealed. This inhibition could be overcome in mostrats if the treatment was pursued for more than 20 weeks. Rats,which during the treatment were exposed to ethanol in an intermittentfashion, had after the treatment a propensity to drink moreethanol in a continuous test. This intake was not influencedbv ethanol concentration and could at least In one rat givemeasurable blood ethanol concentration.     

BUSPIRONE AS AN INHIBITOR OF VOLUNTARY ETHANOL INTAKE IN MALE RATS

The effect of buspirone. a drug with mainly 5-HT_1A-agonist activity,on voluntary ethanol intake was tested in a rat model of alcoholism.In this model the treatment consists of an injection of ethanol(2 0g/kg) or saline once a week, preceded by a 24 h choice betweenwater and ethanol (10%. w/v). This weekly injection of ethanolreduces voluntary ethanol intake in male rats. Maximal inhibitionis seen after 5–6 weeks. At this maximal inhibition buspironeor saline was injected prior to the voluntary 24 h intake ofethanol in both the ethanol- and saline-injected groups Thetested doses were 5 mg/kg (week 5) and 20 mg/kg (week 6). Therewas no reduction in ethanol intake in the buspirone-injectedgroups when compared with their corresponding controls. A secondexperiment with buspirone was performed during the evaluationperiod following treatment with ethanol. This treatment consistedof a choice between water and ethanol (10%. w/v) for 1 day eachweek, followed by an injection of ethanol (2.0g/kg) and lastedfor 52 weeks. During the evaluation period the rats had a continuouschoice between ethanol and water for 37 weeks and no injectionswere given In this situation, with a longer exposure to ethanol.a dose of 20 mg/kg of buspirone in week 90 reduced ethanol intakeby approximately 40%. when compared with controls. The effectof this buspironc dose lasted at least a week. This indicatesthat the long-term exposure to ethanol in the second experimentinduces changes that affect the serotonergic transmission, andthat this changed neural system is involved in the regulationof voluntary ethanol intake.     

THE EFFECT OF DIAZEPAM ON VOLUNTARY ETHANOL INTAKE IN A RAT MODEL OF ALCOHOLISM

This paper reports the effects of a diazepam treatment on voluntaryethanol intake in rats included in an animal model of alcoholism.In a first dose-seeking experiment, rats had a choice between10% (w/v) ethanol and water for 24 h each week. Single dosesof diazepam between 2 and 20 mg/kg injected i.p. prior to the24-h choice caused a dose-dependent decrease in voluntary ethanolintake from 3.2±0.4 g/kg/day down to 2.3±0.3 g/kg/day(P<0.01) after a dose of 20 mg/kg. In a second experiment,psychological dependence was induced by a 1-year intermittentexposure to ethanol (a choice between 10% ethanol and waterfor 24 h each week, followed by an i.p. injection of 2.0 g/kgof ethanol). After this year, the rats were given a continuouschoice between ethanol and water. A 3-week treatment with diazepam(20 mg/kg/day, i.p.) was started in week 68, during which perioda choice of 10% (w/v) ethanol was available only on the firstand the last days of treatment. On the first day of the diazepamtreatment, ethanol intake was decreased from a pre-experimentalvalue of 2.7±0.3 g/kg/day to 1.2±0.1 g/kg/day(P<0.001). On the last day of the treatment, voluntary intakewas higher than before the treatment (3.8±0.27 g/kg/day,P<0.01). Ethanol intake remained elevated during the weekafter the end of the diazepam treatment (P<0.05). When singledoses of diazepam (20 mg/kg) were re-tested 10 and 19 weeksafter the treatment, there was no decrease in ethanol intake,indicating that the initial effect had not been re-established.     

CONSTANT ABSOLUTE ETHANOL INTAKE BY SARDINIAN ALCOHOL-PREFERRING RATS INDEPENDENT OF ETHANOL CONCENTRATIONS

The present study was designed to evaluate ethanol drinkingbehaviour in Sardinian alcohol-preferring (sP) and Sardinianalcohol-non-preferring (sNP) rats in the presence of differentethanol concentrations. Ethanol intake was tested under thetwo-bottle, free-choice regimen and continuous access schedule.Ethanol-naive sP and sNP rats were initially given ethanol solutionat the standard, constant concentration of 10% (v/v) for 8 consecutivedays (Phase 1). As expected, daily ethanol intake in sP ratsrose from 4 to {small tilde}l6g/kg; in contrast sNP rats consumed<10g/kg/day ethanol. Subsequently, an ascending series ofethanol concentrations, ranging from 3 to 60% (v/v), was presentedto sP and sNP rats over a 28-day period (Phase 2). At concentrationsvarying from 7 to 30%, sP rats consumed constant amounts ofabsolute ethanol per kg of body weight ({small tilde}6.0 g/kg/day).Daily ethanol intake in sNP rats remained constantly lower than1.0 g/kg, irrespective of the ethanol concentration. Data fromPhase 2 demonstrate the ability of sP rats to precisely adjustdaily ethanol intake and support the hypothesis that voluntaryethanol drinking in sP rats is sustained by specific pharmacologicaleffects of ethanol.     

EFFECTS OF THE CALCIUM CHANNEL ANTAGONIST DARODIPINE ON ETHANOL WITHDRAWAL IN RATS

The effect of the dihydropyridine calcium channel antagonist,darodipine, on ethanol withdrawal syndrome was examined in ratsmade dependent on ethanol by repeated ethanol administrationfor six consecutive days. Chronic co-administration of darodipineprevented the severity of ethanol withdrawal signs in a dose-dependentfashion. By contrast, acute administration of darodipine duringthe ethanol withdrawal phase was ineffective in reversing thewithdrawal symptoms. The results suggest that the presence ofdarodipine in the central nervous system during the adaptativeresponses to ethanol is necessary to reduce the severity ofthe withdrawal syndrome. They also provide further evidencefor a potential clinical usefulness of dihydropyndine calciumchannel blockers in treatment of ethanol withdrawal.     

DIET AND DIURETICS IN THE REDUCTION OF VOLUNTARY ALCOHOL DRINKING IN RATS

Three rats were trained and given extensive experience withan operant-conditioning model of alcohol self-administrationwhich produces pharmacologically significant drug intake. Inthis model, lever presses on a fixed ratio (FR) schedule ofreinforcement allowed the animal brief access to an 8% (w/v)alcohol solution. Drug intake was then assessed when the animalswere given a low-sodium diet and a low-sodium diet in combinationwith injections of the salt-losing diuretic furosemide (Lasix).In all cases, the low-sodium diet/furosemide treatment produceda substantial reduction in drug self-administration withoutchanging water self-administration. In one case, introducingfurosemide into the home-cage drinking water without a changeof diet also brought about a decrease in alcohol self-administration.The low-sodium diet alone was ineffective in this regard. Thesefindings corroborate earlier work using this form of treatmentand are discussed in terms of the possible functional mode(s)of action of the treatment. The viability of this treatmentfor human drug-taking is also considered.     

HIGH SENSITIVITY TO {lambda}-HYDROXYBUTYRIC ACID IN ETHANOL-PREFERRING sP RATS

Sensitivity to the sedative effect of     

EFFECTS OF 5-HT3 RECEPTOR AGONISTS ON VOLUNTARY ETHANOL INTAKE IN RATS MAINTAINED ON A LIMITED ACCESS PROCEDURE

Recent evidence from a variety of laboratory studies suggeststhat the central effects of ethanol (EtOH) are mediated by serotonin5-HT₃ receptors. Notably, EtOH is able to potentiate 5-HT actionon 5-HT₃ ionophore, and 5-HT₃ antagonists are known to reducecertain effects of EtOH. In the present study, we evaluatedthe effects of two agonists of 5-HT₃ receptors, 2-methyl-5-HT(2-Me-5-HT) and m-chlorophenylbiguanide (m-CPBG) that were microinjectedi.c.v. and into the nucleus accumbens (NAC) on EtOH intake inWistar rats with high EtOH preference. 2-Me-5-HT given i.c.v.(1 and 10 µg per rat) and into the NAC (bilaterally 1and 10 µg per site) significantly reduced EtOH intakein the limited access paradigm (2 h session). On the other handm-CPBG was inactive after intra-NAC administration. It is concludedthat central 5-HT₃ receptors are involved in the regulationof EtOH consumption.     

长期酒精摄入对大鼠胰岛素分泌功能的影响

目的:研究长期酒精摄入对大鼠血糖、血清胰岛素及胰岛素基因表达影响。方法:清洁级Wistar大鼠80只,雌雄各半,随机分为对照组和低、中、高剂量组,摄入酒精剂量分别为0、0.8、1.6和2.4g/(kgbw?d)。给予酒精18w后,进行口服葡萄糖耐量试验(OGTT),第19w末,断头处死,测定空腹血糖和血胰岛素水平,计算Homa-β功能指数(HBCI)。提取胰腺总RNA,半定量RT-PCR测定胰岛素mRNA表达水平。结果:雌性大鼠高剂量组空腹血糖升高、空腹血清胰岛素下降,中、高剂量组HBCI及胰岛素基因表达均降低;雄性大鼠OGTT高剂量组0和1.5h血糖升高,空腹血糖高剂量组升高,低、中剂量组空腹血胰岛素升高,随着剂量增加,HBCI及胰岛素基因表达先升高后降低。结论:长期高剂量酒精摄入可导致胰岛素mRNA基因表达改变,胰岛β细胞功能受损。     

长期酒精摄入引起大鼠胰岛素抵抗及其分子机制

目的研究酒精摄入与胰岛素敏感性之间的关系并深入探讨其相关的分子机制。方法清洁级Wistar大鼠80只(雌雄各半),按体重随机分为对照组和低、中、高剂量共4组,每天摄入酒精剂量分别为0、0.8、1.6、2.4g/(kg·bw)。第19w末,断头处死大鼠,测定空腹血糖和血胰岛素,计算HOMA胰岛素抵抗指数(HOMA-IR)。提取肝组织,通过Western blot方法测定磷脂酰肌醇3激酶p85亚单位(p85subunit of phosphoinositide3-kinase,PI-3Kp85),葡萄糖转运体2(Glucose transporter-2)蛋白表达水平。结果与对照组相比,雄性大鼠高剂量组空腹血糖升高,低、中剂量组空腹胰岛素水平升高,各酒精剂量组HOMA-IR指数均升高PI3-K、GLUT-2蛋白在高剂量组表达降低;与对照组比较,雌性大鼠高剂量组空腹血糖升高、空腹血胰岛素下降。各剂量组HOMA-IR指数与对照组比较差异无显著性,PI3-K、GLUT-2蛋白在中,高酒精剂量组的表达均降低。结论长期酒精摄入可以引起胰岛素抵抗,肝脏PI-3K(p85),Glu-4蛋白表达水平的降低,可能是酒精胰岛素抵抗的分子机制之一。     

SEROTONIN IS REDUCED IN THE FRONTAL CORTEX OF SARDINIAN ETHANOL-PREFERRING RATS

Ethanol-naive Sardinian alcohol-preferring (sP) and Sardinianalcohol-non-preferring (sNP) rats were tested to evaluate thelevels of serotonin (5-HT) and 5-hydroxyindol-3-yl-acetic acid(5-HIAA) in the frontal cortex, hypothalamus, and nucleus accumbens,and the levels of dopamine (DA) and 3,4-dihydroxyphenylaceticacid (DOPAC) in the hypothalamus and nucleus accumbens. Comparedwith the sNP line, the sP rats had lower 5-HT and 5-HIAA concentrationsin the frontal cortex, whereas no differences were found inthe other brain areas tested, neither for neurotransmittersnor their metabolites. As the decreased 5-HT function is a featureshared by different alcohol-preferring strains, it could belinked to the genetic predisposition to voluntary ethanol consumption.     

SUPPRESSION BY GAMMA-HYDROXYBUTYRIC ACID OF ETHANOL WITHDRAWAL SYNDROME IN RATS

The ability of gamma-hydroxybutyric acid to suppress ethanolwithdrawal syndrome was tested in male rats rendered physicallydependent on ethanol by several intragastric administrationsof ethanol (9–15 g/kg daily for 7 days). Gamma-hydroxybutyrate(0.25, 0.50 and 1.00 g/kg i.p.), administered 8 hr after thelast ethanol dose, produced a dose-dependent inhibition of withdrawalsigns such as tremors and audiogenically-induced seizures; thehighest dose tested suppressed all ethanol withdrawal symptoms.     

REDUCTION IN STRIATAL 5-HYDROXYTRYPTAMINE TURNOVER FOLLOWING CHRONIC ADMINISTRATION OF ETHANOL TO RATS

Male Sprague–Dawley rats were given 10% (v/v) ethanolto drink for 28 days and the effects of the drug on the brain5-hydroxytryptamine (5-HT) turnover were studied. Turnover wasdecreased in the corpus striatum after ethanol treatment dueto a decrease in 5-hydroxyindol-3-ylacetic acid (5-HIAA), andan increase in 5-HT, concentration. Noradrenaline concentrationwas also increased in this region, but those of dopamine andGABA were similar to control values. Ethanol had no effect onany of the neurotransmitters studied in the brain stem and hippocampus,nor on the activity of monoamine oxidase type A (MAO-A) and5-HT uptake in the three brain regions. Chronic ethanol administrationcaused a selective decrease in striatal 5-HT turnover whichwas unrelated to either its rate of inactivation, or the activityof other brain neurotransmitters. These findings are discussedin relation to those obtained in previous studies.     

PREVENTION BY CYCLOHEXIMIDE OF THE AUDIOGENIC SEIZURES AND TRYPTOPHAN METABOLIC DISTURBANCES OF ETHANOL WITHDRAWAL IN RATS

Cycloheximide (20 mg/kg body wt, given intraperitoneally at—1 and 3 h after withdrawal of an ethanol-containing liquiddiet) prevents the activation of liver tryptophan pyrrolase,the consequent inhibition of synthesis of brain 5-hydroxytryptamine,and the audiogenic seizures observed at 7 h after alcohol withdrawal.We suggest that a rapidly-turning-over protein mediates thealcohol withdrawal syndrome and discuss the possible role ofliver tryptophan pyrrolase.     

RECITATION OF SALT INTAKE IN RATS

Bilateral lesions in the ventredial nuclei of the hypothalamus impair rat's ability to sense sodium depletion.     

THE LIVER PEPTIDES AFTER CHRONIC ADMINISTRATION OF ETHANOL IN RATS

The liver peptide fractions labelled with ³H-arginine afterchronic administration of ethanol to rats have been analysedby gel filtration chromatography and tlc. Specific ³H-arginineradioactivity in the liver peptide fraction calculated per µgof -amino nitrogen was significantly decreased by alcohol. Theamount of peptide spots obtained by tlc in the ethanol-treatedgroup was reduced in comparison with the control group. Thefindings suggest a change in the protein metabolism in hepaticdysfunction in rats receiving ethanol over a prolonged period.     

THE EFFECT OF CHRONIC ETHANOL CONSUMPTION ON IRON ABSORPTION IN RATS

Alcoholics often have an increased amount of iron in the liverwhich may contribute to the development of alcoholic liver disease,although the mechanism is unknown. It has been shown that chronicethanol intake decreases the enterocyte turnover and enhancesgalactose absorption. Whether it affects iron absorption isstill controversial. The aim of this study was to investigatethe effect of chronic ethanol ingestion on whole body iron absorptionin rats. Twenty-eight adult male Sprague-Dawley rats were pair-fed aliquid diet containing either ethanol as 36% of total caloriesor an isocaloric diet where fat was substituted, for ethanol.On the 28th day, four-hour fasted rats were given an oral doseof ⁵⁹Fe (0.5µCi) and were immediately counted by a wholebody counter. ⁵⁹Fe levels were then monitored over the followingnine days. Although ethanol- and control-fed rats had a similarhepatic iron content (59.5±5.8 vs 60.2±7.4 µg/100mg dry liver weight) (mean±S.E.M.), the ⁵⁹Fe total bodycontent was greater in the ethanol group (75%±3%) comparedwith the control group (45%±4%). These results show thatchronic ethanol ingestion increased iron absorption in rats.A reduction of enterocyte turnover may play a role in determiningthis effect.     

OCCURRENCE IN VIVO OF 5-HYDROXYTRYPTOPHOL IN THE BRAIN OF RATS TREATED WITH ETHANOL

The effect of ethanol (EtOH) on the release of dopamine (DA)and 5-hydroxytryptamine (5-HT) and the efflux of their metabolites,3, 4-dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindol-3-ylaceticacid (5-HIAA) and 5-hydroxytryptophol (5-HTOL) from the striatumof the freely moving rat were studied in vivo using brain microdialysis.Striatal DA and 5-HT release was maximally enhanced at firstfraction after the administration of EtOH (2 g/ kg, i.p.). Thelevel of the DA-oxidized metabolite, DOPAC, decreased significantly.In the 5-HT metabolic pathway, the oxidized metabolite, 5-HIAA,did not show significant changes, whereas levels of the biogenicalcohol 5-HTOL were increased to 180% at 90 min following EtOHadministration. It is suggested that EtOH, most probably viaacetaldehyde, could shift 5-HT metabolism from the oxidativeto the reductive pathway in the rat brain.     

锌和维生素A对酒精致大鼠睾丸损伤的保护作用

[目的]观察锌和维生素A(VA)对长期摄入酒精致大鼠睾丸损害的保护作用及可能机制.[方法]40只健康雄性成年SD大鼠随机分为对照组、酒精组、酒精+葡萄糖酸锌组、酒精+VA组,各组每日分别灌胃给予酒精0、7.5 g/kg、酒精7.5 g/kg+葡萄糖酸锌7.7mg/kg、酒精7.5 g/kg+VA50μg/kg,连续13周.对各组大鼠的精子计数、精子活动率、精子畸形率、血清睾酮(T)、黄体生成素(LH)、卵泡刺激素(FSH)含量进行检测,光、电镜观察睾丸的形态改变.同时测定睾丸线粒体中丙二醛(MDA)的产生量,免疫组织化学法检测睾丸组织中iNOS的表达.[结果]与对照组相比,酒精组大鼠精子计数减少,精子活动率下降,精子畸形率升高(P＜0.05),血清T、LH、FSH水平明显降低(P＜0.05);睾丸生精上皮结构破坏,支持细胞和各级生精细胞均有退化变性;睾丸生精细胞iNOS表达明显增强(P＜0.05);睾九线粒体丙二醛含量明显升高(P＜0.05).与酒精组相比,葡萄糖酸锌组和VA组精子计数、精子活动率有所上升,生精细胞退化变性程度减轻,睾丸生精细胞iNOS表达减弱(P＜0.05),睾丸线粒体MDA减少,但血清T、LH、FSH水平仍低于对照组.[结论]长期摄入酒精不仅抑制精子发生和睾酮合成,还使下丘脑-垂体轴生殖内分泌功能受损.补充锌和VA可以限制酒精引起的睾丸过氧化损伤,保护睾丸的生精功能,但仍有生殖内分泌激素合成障碍.     

THE INFLUENCE OF CHRONIC ETHANOL ADMINISTRATION ON ADRIAMYCIN-INDUCED NEPHROTIC SYNDROME IN RATS

Alcoholic liver disease may be frequently complicated by mesangialproliferation with the deposition of IgA in glomeruli and glomeruloscierosis,but these glomerular lesions are usually mild and without greaterimpact on renal function. To evaluate the putative role of ethanolin glomerular pathology we studied the influence of chronicethanol administration on the development of experimental adriamycinnephropathy in rats. Nephrotic syndrome was induced by a singlei.v. dose of adriamycin (5 mg/kg body wt) both in rats givenethanol at a dose of 4 g/day for 3 months and control rats givenstandard chow. Further controls on both diets without adriamycinadministration were also studied. Blood and urine were examinedbefore and 3 and 6 weeks after adriamycin administration. Allrats were killed and examined histologically 6 weeks after adriamycinadministration. Ethanol fed nephrotic rats were more catabolicthan control nephrotic rats (with higher free fatty acids, lowerglycaemia, higher urea with similar creatinine) and had lowerproteinuria (0.55 ± 0.34 versus 5.79 ± 3.15 gof protein/mmol of creatinine, P<0.05), higher albuminaemia(5.41 ± 2.62 versus 1.92 ± 1.94 g/l, P<0.01),lower plasma cholesterol (6.54 ± 2.6 versus 10.57 ±2.92 mmol/l. P<0.01) and triglycerides. The development ofnephrotic syndrome and renal morphological changes after adriamycinadministration in rats seemed to be ameliorated, or at leastdelayed by chronic ethanol feeding with much milder and focalglomerulosclerosis as compared with more severe and diffuseglomerulosclerosis in control nephrotic animals. The mechanismof this effect of chronic ethanol feeding remains to be elucidated.Metabolic, immunosuppressive and pharmacological effects ofethanol should be taken into consideration.