Stable preference for high ethanol concentrations after ethanol deprivation in Sardinian alcohol-preferring (sP) rats.

Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.     

Effects of ethanol administration on corticosterone levels in adolescent and adult rats

Adolescent humans and rodents have been shown to consume more alcohol than their adult counterparts. Given that corticosterone (CORT) has been shown to be related to the intake of several drugs of abuse, this study assessed the ontogenetic effects of low-moderate doses of ethanol on CORT increases and recovery. Despite no significant differences in baseline (home cage) CORT levels, CORT responses to ethanol were greater in females than in males and in adult females than in adolescent females; males, however, showed less marked age differences in CORT levels after ethanol consumption. Adolescent blood ethanol concentrations (BECs) were lower than those of adults, although these BEC differences appear insufficient to account for the ontogenetic differences in CORT levels. Collectively, these findings suggest that it is unlikely that age differences in CORT elevations provide a major contribution to the ontogenetic differences in alcohol intake seen between adolescents and adults.     

Tetrahydropapaveroline in brain regions of rats after acute ethanol administration

Tetrahydropapaveroline (THP), the condensation product of dopamine, and its aldehyde, dopaldehyde, have been detected in brain regions of rats after acute ethanol administration. THP levels were determined in eight brain regions of animals that received ethanol (3.0 g/kg) by intraperitoneal injection 100 or 120 minutes before decapitation. The levels of THP in two brain regions, i.e., the midbrain and striatum, were determined at time intervals ranging from 50 to 120 minutes after ethanol administration. THP was not found in brain regions of untreated animals. However, significant levels of THP were found in pooled midbrains (0.50 pmol/g tissue) and pooled hypothalami (0.20 pmol/g tissue) of animals that received ethanol 120 minutes before decapitation. Most brain regions had detectable levels of THP 100 minutes after the animals received ethanol and the striatum contained the highest concentration of the alkaloid. The concentration of THP in striata tissue of rats at 50, 70, 90, or 100 minutes after ethanol administration were 0.33, 0.38, 0.33, and 0.33 pmol/g tissue, respectively. These results demonstrate that THP can be detected in specific brain regions of the rat after acute ethanol administration.     

Hepatic catalase and superoxide dismutases after acute ethanol administration in rats

The administration of an acute ethanol load (2.3 g/kg, IP) to rats is followed by a decrease of the hepatic activity of cytosolic catalase, a decrease which precedes a reduction in the cytosolic Cu, Zn-superoxide dismutase (SOD) activity. Desferrioxamine, an iron chelator and scavenger of superoxide radicals, administered prior to ethanol, prevents the changes in the cytosolic catalase activity, changes which are unaffected by the administration of allopurinol, an inhibitor of xanthine oxidase. These data favour the hypothesis that acute ethanol results in an overproduction of oxygen free radicals which affects primarily the cytosolic catalase activity and increases hereby susceptibility of Cu, Zn-SOD to these radicals. They suggest also that xanthine oxidase does not play a major role in oxygen radical production in the liver cytosol during acute alcohol intoxication.     

Effects of adolescent ethanol exposure on ethanol consumption in adult rats.

Ethanol exposure during early development could predispose an individual to increased ethanol consumption. Given the high prevalence of adolescent ethanol abuse, it is important to assess the potential impact of adolescent ethanol exposure on the development of alcohol drinking. The following study was designed to assess the initiation of ethanol consumption in adult rats after exposure to ethanol vapors during adolescence. Male Sprague-Dawley rats (n = 23) were exposed to ethanol vapor for 12 h per day for 10 consecutive days between postnatal days 30 and 40. Ethanol vapor exposure maintained blood ethanol levels averaging 250 mg/dl. All rats were subsequently trained to self-administer ethanol after a 52-day withdrawal period. When ethanol consumption was assessed in the adult rats (>3 months old) there were no significant differences in initiation or maintenance of ethanol self-administration between ethanol-exposed and control rats. In addition, there were no group differences in the ability of a noise stressor presented before the drinking session to transiently decrease ethanol intake. Overall, these findings indicate that forced exposure to ethanol vapor during adolescence does not seem to be sufficient to alter initiation or maintenance of limited-access ethanol self-administration.     

Effects of acute administration of ethanol on cerebral glucose utilization in adult alcohol-preferring and alcohol-nonpreferring rats.

Local cerebral glucose utilization (LCGU) rates, as determined by the [(14)C]-2-deoxyglucose (2-DG) technique, were examined after acute ethanol administration within selected brain regions of alcohol-preferring (P) and alcohol-nonpreferring (NP) rats. Adult male P and NP rats were injected with saline, 0.25 g/kg, or 1.0 g/kg ethanol, intraperitoneally (ip), 10 min before an intravenous bolus of [(14)C]2-DG (125 microCi/kg). Timed arterial blood samples were collected over 45 min and assayed for plasma glucose, ethanol, and [(14)C]2-DG levels. Image densities were determined using quantitative autoradiography and LCGU values calculated. Data were collected from several key limbic, basal ganglionic, cortical, and subcortical structures. Low-dose ethanol (0.25 g/kg) significantly decreased LCGU rates in several brain regions including the medial prefrontal cortex, olfactory tubercles, and the CA1 subregion of the hippocampus of P rats. Low-dose ethanol had no significant effects on LCGU rates in the NP rats. Moderate-dose ethanol (1.0 g/kg) also significantly lowered LCGU rates in many brain regions of P rats, including key limbic structures, such as the medial prefrontal cortex, olfactory tubercles, ventral tegmental area, basolateral nucleus of the amygdala, lateral septum, and ventral pallidum. Moderate-dose ethanol also significantly lowered LCGU rates in the medial prefrontal cortex as well as in the habenula of NP rats. All other regions were unaffected in the NP rats. These findings support the suggestion that certain central nervous system regions of P rats may be more sensitive than those of NP rats to the effects of low to intermediate doses of ethanol.     

Periodicity of chronic ethanol administration as a variable in the induction of dependence in rats

The effect of periodicity of chronic ethanol intragastric administrations on the induction of physical and behavioral dependence on ethanol has been assessed in two groups of rats. In the two groups, rats initially selected for an identical sensitivity to ethanol, were administered daily 10 g per kg b.w. during 15 days. In one group, this daily dose was administered in six intragastric pulses of 1.7 g/kg each, 3 hours apart. In the other group, the same 10 g/kg daily dose was administered in three pulses of 3.33 g/kg, 6 hours apart. In control rats determinations of blood ethanol level in these two treatment conditions showed that the daily area of blood alcohol was 2.5 times higher in the first condition than in the second one. After the 15 days of chronic forced administration, experimental rats were subjected during 6 days to an alternate eight hours single bottle presentation of 10% ethanol solution and water. In this final test of the induced behavioral dependence, rats chronically treated by small frequent doses, displayed the highest intake of ethanol solution versus water. It is concluded that periodicity of a chronic administration or intake of ethanol is an important parameter in the induction of dependence, and the frequent administration of a small daily dose distributed in higher and less frequent unitary administrations.     

Effects of chronic naltrexone treatment in rats on place preference and locomotor activation after acute administration of cocaethylene or ethanol plus cocaine.

When cocaine and ethanol are taken together a cocaine metabolite called cocaethylene is produced. Investigators have determined that cocaine, ethanol, and cocaethylene all produce a conditioned place preference when administered intraperitoneally. On the basis of the moderate success of naltrexone at attenuating the rewarding effects of ethanol and cocaine administered independently, we examined the ability of chronic naltrexone treatment (administered by means of subcutaneous implant across 6 days) to reduce the preference and motor-stimulating effects resulting from intraperitoneal administration of cocaethylene (Experiment 1) and the co-administration of ethanol with cocaine (Experiment 2) in outbred rats. Results demonstrated naltrexone modestly reduced conditioned place preference for cocaethylene but had no effect on the locomotor stimulation resulting from cocaethylene administration. Naltrexone failed to decrease the preference for the chamber paired with co-administration of ethanol and cocaine and did not change the degree of locomotor activation produced by these drugs. These results support the suggestion that naltrexone as a pharmacotherapy to treat co-abuse of ethanol and cocaine in human beings may have limited benefits.     

Effect of chronic ethanol administration on disposition of ethanol and its metabolites in rat.

We studied the effects of chronic alcohol intake on the disposition of alcohol and its metabolites in the rat. We used male Wistar rats for all of the experiments in this study. Using a pair-feeding process, rats were fed a liquid diet containing alcohol or without alcohol for 6 weeks. Ethanol solutions (0.5, 1.0, 1.5, and 2.0 g/kg body weight [BW]) were administered as a bolus, intravenously. We then measured blood ethanol and acetate concentrations. Simultaneous multiline fitting was performed using mean blood alcohol concentration (BAC)-time curves fitted to the one-compartment open model with parallel first-order and Michaelis-Menten elimination kinetics. At low doses (0.5, 1.0, and 1.5 g/kgBW), no differences were observed between the alcohol group and the control group with respect to ethanol elimination rate, area under the curve of ethanol (AUC(EtOH)), and mean residence time of ethanol (MRT(EtOH)). At higher doses (2.0 g/kgBW), ethanol elimination rate in the alcohol group was significantly higher than in the control group (P<.5%). These findings were also substantiated by corresponding changes in AUC(EtOH) and MRT(EtOH). At low doses, no differences were observed between the alcohol group and the control group with respect to plateau concentration of acetate (AcT) (concentration of steady state=C(ss)AcT), area under the curve of AcT (AUC(AcT)), and mean residence time of AcT (MRT(AcT)). However, at higher doses, although there were no differences in C(ss)AcT, both AUC(AcT) and MRT(AcT) were significantly lower in the alcohol group when compared to the control group (P<.5%). Chronic alcohol consumption increases ethanol oxidation and AcT metabolism in rats, as observed at high blood alcohol concentrations (BACs). These effects were observed at BACs of 3.5-4.5 mg/ml, and were not observed at lower doses. Thus, with general alcohol consumption, interindividual differences and intra-individual changes in alcohol metabolism may not take into account increased or accelerated metabolism due to alcohol tolerance.     

Formation of ethyl nitrite in vivo after ethanol administration.

The purpose of the current study was to ascertain whether ethyl nitrite could be detected in vitro from the reaction of ethanol with peroxynitrite, as well as after administration of ethanol to mice. Ethyl nitrite analyte was determined by using gas chromatography--mass spectrometry with headspace analysis with the use of a solid-phase microextraction device. Peroxynitrite was allowed to react with ethanol under a variety of conditions in vitro. Ethyl nitrite was generated when peroxynitrite was allowed to react with ethanol. Male, inbred short-sleep mice were injected intraperitoneally with either ethanol [5.2 g/kg; 15.0% (weight/volume) ethanol in saline] or a 50:50 mixture of deuterium-labeled ethanol (D5-ethanol) and ethanol. Blood samples, as well as whole brain and liver sections, were obtained from mice 30 min later for determination of ethanol, D5-ethanol, ethyl nitrite, and deuterium-labeled ethyl nitrite (D5-ethyl nitrite). Time courses for the appearance of ethyl nitrite in blood samples, as well as in whole brain and liver sections, obtained from mice were carried out. After ethanol administration, ethyl nitrite was detected and quantitated in mouse blood, brain, and liver. A small fraction of ethyl nitrite was present. When a 50:50 mixture of ethanol and D5-ethanol was given to animals, both ethyl nitrite and D5-ethyl nitrite were found in blood and brain in approximately the same ratio as that of ethanol and D5-ethanol. The level of D5-ethyl nitrite in liver was more than twice that of ethyl nitrite, indicating a possible isotope effect in the metabolism of ethyl nitrite. Ethyl nitrite is a new metabolite of ethanol in vivo. The mechanism of ethyl nitrite formation is most likely the reaction of ethanol with peroxynitrite generated in vivo from nitric oxide.     

Sensitization to social anxiolytic effects of ethanol in adolescent and adult Sprague-Dawley rats after repeated ethanol exposure

Ontogenetic studies using a social interaction paradigm have shown that adolescent rats are less sensitive to anxiolytic properties of acute ethanol than their adult counterparts. It is not known, however, whether adaptations to these anxiolytic effects on repeated experiences with ethanol would be similar in adolescents and adults. The present study investigated sensitivity to the anxiolytic effects of ethanol in adolescent and adult male and female Sprague-Dawley rats after 7 days of exposure (postnatal day [P] 27-33 for adolescents and P62-68 for adults) to 1 g/kg ethanol or saline (intraperitoneally]) and in animals left nonmanipulated during this time. Anxiolytic effects of ethanol (0, 0.75, 1.0, 1.25, and 1.5 g/kg for adolescents and 0, 0.25, 0.5, 0.75, 1.0, and 1.25 g/kg for adults in experiments 1 and 2, respectively) were examined 48 h after the last exposure using a modified social interaction test under unfamiliar test circumstances. At both ages, repeated ethanol exposure resulted in the development of apparent sensitization to anxiolytic effects of ethanol, indexed by enhancement of social investigation and transformation of social avoidance into social indifference or preference and expression of tolerance to the socially inhibiting effects induced by higher ethanol doses. Evidence for the emergence of sensitization in adults and tolerance at both ages was seen not only after chronic ethanol but also after chronic saline exposure, suggesting that chronic manipulation per se may be sufficient to alter the sensitivity of both adolescents and adults to socially relevant effects of ethanol.     

The effect of chronic ethanol administration on lipogenesis in liver and adipose tissue in the rat

Rates of lipogenesis de novo have been studied in liver and epididymal fat pads of male rats chronically treated with ethanol. A solution of ethanol (150 ml/l) was administered as the only drinking fluid for 3 months with a standard solid diet; both food and drink were available ad lib. Lipogenesis in vivo was measured by the incorporation of tritiated water into lipid fractions: non-saponifiable lipid and fatty acids. Non-saponifiable lipid, both in liver and in adipose tissue, was unaffected by ethanol treatment. However, fatty acid synthesis de novo was significantly enhanced in both liver and adipose tissue, by 150 and 300% respectively. Plasma triacylglycerol and non-esterified fatty acid levels were unchanged and plasma glucose concentration slightly increased by ethanol administration. The rate of lipogenesis increased when insulin: glucagon increased twofold due to the effect of ethanol.     

Absence of effect of 3-amino-1,2,4-triazole pretreatment on blood ethanol levels after oral administration, in rats

Blood ethanol levels registered in rats receiving 90 mmole/kg by gavage were not different in rats pretreated with aminotriazole (1 g/kg IP) 1 hour before, than in untreated controls. Results are consistent with the idea that no measurable gastrointestinal catalase first pass effect is present in rats.     

T-cell activation after chronic ethanol ingestion in mice.

Chronic excessive consumption of ethanol causes immunodeficiency in human beings and in mice. Immunologic changes have been described in both species, including T-cell and innate immune system cell activation, among others. The features of chronic ethanol-induced activation have similarities in the two species, including an increased effector subset in both CD4+ and CD8+ T cells. There are also features of activation observed in the splenic macrophages of mice consuming ethanol chronically, including increased up-regulation of CD80 and CD86. Because these molecules are involved in T-cell-antigen-presenting cell interactions in vivo, it is of interest to ask whether these and other pathways of interaction are important in the T-cell activation and cytokine skewing described in chronic ethanol abuse. Preliminary findings from comparisons of wild-type, CD40 ligand knock-out, and CD28 knock-out C57BL/6 mice strongly support the suggestion of a critical role for T-cell-antigen-presenting cell interactions in the immune alterations observed in chronic ethanol abuse.     

Effects of chronic ethanol exposure on sleep in rats.

Sleep disturbance is a common complaint in alcoholics. When polysomnographic studies are performed in alcoholics, reductions in slow wave sleep are a common finding; however, few studies have evaluated the effects of chronic alcohol exposure on sleep in animal models. In the present study, the sleep EEG was evaluated in 40 Wistar rats who were exposed to chronic alcohol or control conditions in vapor chambers. Rats were exposed to ethanol vapors or control chambers for 6 weeks and then withdrawn. Sleep EEG was recorded before exposure (baseline), immediately following exposure, and 5 weeks after withdrawal from the ethanol/control chambers. In the ethanol-exposed animals, blood ethanol levels averaged 192 mg/dL over 6 weeks of exposure. Chronic ethanol exposure and withdrawal was not found to affect either slow wave sleep latency or slow wave sleep duration; however, overall spectral power as well as power in the delta, theta, and beta frequencies were significantly reduced following chronic exposure (2-4 Hz, [F(1, 17) = 18.11, p = 0.001], 4-6 Hz, [F(1, 17) = 15.98, p = 0.001], 6-8 Hz [F(1, 17) = 15.52, p = 0.001], 8-16 Hz band [F(1, 17) = 18.73, p < 0.0001], 16-32 Hz [F(1, 17) = 10.13, p = 0.005], and 1-50 Hz [F(1, 17) = 17.03, p = 0.001]. After 5 weeks of withdrawal, significant decreases still persisted in the delta and theta frequencies (2-4 Hz [F(1, 16) = 6.21, 0.024], 4-6 Hz [F(1, 16) = 6.26, 0.024], and 6-8 Hz [F(1, 16) = 4.84, p = 0.043]). These findings suggest that spectral analysis of the EEG is a highly sensitive measure of the effects of ethanol on sleep. These findings additionally demonstrate that chronic ethanol exposure can produce persistent diminution in the systems that generate cortical slow waves in the rat and thus may provide a model for understanding the mechanisms underlying sleep disturbances associated with alcoholism.     

Ganglioside long-chain base composition of rat brain subcellular fractions after chronic ethanol administration

Rats of two different ages (2 and 7 months) were treated with an ethanol-containing liquid diet for 24 days and changes of the ceramide composition of gangliosides were studied in the brain synaptosomal, microsomal and myelin fractions. Greater differences were observed in the younger age, where ethanol treatment caused a significant increase of C20: 1 LCB in GM1 ganglioside of synaptosomes and microsomes and in GDla of myelin.     

Alterations in hepatic delta-aminolevulinic acid synthetase and heme oxygenase activities after chronic ethanol consumption in rats.

In the present study, the effect of chronic ethanol consumption in rats on the hepatic heme metabolism was investigated. Male Wistar rats were fed a nutritionally adequate liquid diet containing ethanol as 36% of the total calories for 5 weeks. After an overnight fast, the livers were excised and centrifuged to obtain mitochondrial and microsomal fractions. Chronic ethanol feeding of rats resulted in about 19% hepatomegaly as represented by the increased liver/body weight ratio. There was no difference in the mitochondrial protein content between the ethanol-treated and control rats, but the microsomal protein content was significantly increased in the ethanol-treated rats. Hepatic microsomal content of cytochrome P-450 (P-450) was markedly enhanced by chronic ethanol ingestion. Microsomal contents of cytochrome b5 (b5) and total heme were also increased to a lesser extent. After chronic ethanol abuse, the hepatic activity of delta-aminolevulinic acid (ALA) synthetase, which is a rate-limiting enzyme for heme production, was significantly increased and that of the heme oxygenase was slightly increased. These data indicate that ALA synthetase activity is induced by the negative feedback mechanism in order to compensate the depletion of heme caused by the utilization of heme for P-450. It is also speculated that, in response to excessive production of heme as described above, heme oxygenase activity is secondarily induced to regulate the amount of heme.     

Effect of chronic ethanol administration on thiamin metabolism in the rat

The effect of chronic alcohol administration on the absorption, excretion and metabolism of thiamin in the rat has been examined. In ethanol-fed rats receiving a marginal daily intake of thiamin (10 microgram/day) by stomach tube or by intraperitoneal injection, less of the vitamin and its metabolites were excreted in the urine as compared to controls administered the same diet except that sucrose replaced the energy represented by ethanol. More of the oral dose of thiamin was excreted in the feces of the ethanol-fed as compared to control rats. These data support previous reports of decreased adsorption of thiamin from the gut in animals exposed to ethanol. The studies in which the thiamin was administered by intraperitoneal injection also indicate an effect of ethanol on thiamin excretion in the urine which appears not to be related to absorption of the vitamin from the gut. An examination reveals no difference in the level of thiamin and its metabolites in the tissues of ethanol-fed as compared to control rats receiving thiamin by stomach tube. Thus, the decreased absorption of thiamin from the gut in the ethanol-fed rats seems to be balanced by a decreased excretion in the urine leading to a comparable accumulation of the vitamin in the tissues as controls.