And Alcohol-avoiding Research Articles

The quinoline compound, S4 effectively antagonizes alcohol intake in mice: Possible association with the histone H3 modifications

Opioidergic system plays an important role in controlling alcohol seeking behavior. We have previously shown that a quinoline compound, S4 (2-(2-methylquinolin-4-ylamino)-N-phenyl acetamide), having dual affinity for µ- and κ-opioid receptors, could successfully inhibit withdrawal symptoms in mice rendered dependent on morphine. Accordingly, in the present study, we sought to determine the potential of S4 in attenuating voluntary alcohol intake in alcohol-preferring (AP) mice and the mechanism thereof. The study was conducted in different mice strains initially screened for AP and alcohol-avoiding (AA) behavior. S4 was injected subcutaneously (20 mg/kg) to evaluate its efficacy in reducing voluntary alcohol consumption along with prevention of body weight loss during withdrawal from alcohol after discontinuation of the drug. The results showed that S4 significantly reduced the alcohol intake in AP mice and also in a dose dependent manner. Mechanistic studies on the post translational histone H3 modifications in brain of AP mice compared to the AA mice were determined. Compared to AA mice, histone H3 trimethylation at lys9 and its regulators, jumonji domain containing 2A and phosphorylated histones H3 at thr11 as well as the expression of 14-3-3 protein and phosphorylated histones H3 at ser28, were altered in the AP animals, most of which were restored post S4 treatment in the AP mice. Together, the present results suggest that S4 effectively blocked alcohol drinking behavior by restoring the altered epigenetic signature in the AP mice. The study provides a novel compound which could lead to developing effective drugs against alcoholism/alcohol abuse.

Accumbal FosB/ΔFosB immunoreactivity and conditioned place preference in alcohol-preferring AA rats and alcohol-avoiding ANA rats treated repeatedly with cocaine

Transcription factor ΔFosB has been implicated in the psychomotor responses and rewarding effects of drugs of abuse. In the present study, we compared the effects of cocaine on the expression of ΔFosB-like proteins by immunohistochemistry in striatal brain areas of alcohol-preferring (AA) and alcohol-avoiding (ANA) rats. Cocaine was administered using a previously verified treatment paradigm that sensitized the locomotor response to cocaine in AA but not in ANA rats. We also studied the rewarding effects of cocaine with a conditioned place preference (CPP) paradigm in both lines of rats. Cocaine treatment increased the FosB/ΔFosB immunoreactivity (IR) in the nucleus accumbens of AA rats but not in ANA rats. In addition, after repeated saline injections the accumbal FosB/ΔFosB IR was significantly greater in saline-injected AA rats than in ANA rats. In the caudate–putamen cocaine significantly increased FosB/ΔFosB IR, but no differences were found between the rats of two lines. In the CPP experiment, AA rats treated with cocaine 2.5 mg/kg preferred the cocaine-associated compartment, in contrast to ANA rats, which did not show such a preference. In conclusion, our findings show that AA rats are more sensitive to cocaine than ANA rats, and suggest that one possible mediator for this increased sensitivity could be the increased expression of fosB-derived proteins in the nucleus accumbens of AA rats.

EVIDENCE OF ACETALDEHYDE-PROTEIN ADDUCT FORMATION IN RAT BRAIN AFTER LIFELONG CONSUMPTION OF ETHANOL

Acetaldehyde, the first metabolite of ethanol, has been shown to be capable of binding covalently to liver proteins in vivo, which may be responsible for a variety of toxic effects of ethanol. Acetaldehyde-protein adducts have previously been detected in the liver of patients and experimental animals with alcoholic liver disease. Although a role for acetaldehyde as a possible mediator of ethanol-induced neurotoxicity has also been previously suggested, the formation of protein-acetaldehyde adducts in brain has not been examined. This study was designed to examine the occurrence of acetaldehyde-protein adducts in rat brain after lifelong ethanol exposure. A total of 27 male rats from the alcohol-preferring (AA) and alcohol-avoiding (ANA) lines were used. Four ANA rats and five AA rats were fed 10-12% (v/v) ethanol for 21 months. Both young (n = 10) and old (n = 8) rats receiving water were used as controls. Samples from frontal cortex, cerebellum and liver were processed for immunohistochemical detection of acetaldehyde adducts. In four (two ANA, two AA rats) of the nine ethanol-exposed rats, weak or moderate positive reactions for acetaldehyde adducts could be detected both in the frontal cortex and cerebellum, whereas no such immunostaining was found in the remaining five ethanol-treated rats or in the control rats. The positive reaction was localized to the white matter and some large neurons in layers 4 and 5 of the frontal cortex, and to the molecular layer of the cerebellum. Interestingly, the strongest positive reactions were found among the ANA rats, which are known to display high acetaldehyde levels during ethanol oxidation. We suggest that acetaldehyde may be involved in ethanol-induced neurotoxicity in vivo through formation of adducts with brain proteins and macromolecules.

Effect of adrenalectomy and exposure to corticosterone on alcohol intake in alcohol-preferring and alcohol-avoiding rat lines.

The daily fluid intake of male rats of the alcohol-preferring (AA) and alcohol-avoiding (ANA) lines with simultaneous access to 10% (v/v) ethanol and water was determined during a baseline period (2 weeks), following adrenalectomy (1 week), and for 2 weeks following corticosterone treatment. The results showed that adrenalectomized AA rats decreased their ethanol intake compared to the sham-operated AA controls and that treatment with corticosterone restored the intake of ethanol to that observed during the baseline period. In contrast to the AA rats, there were no alterations in ethanol intake after adrenalectomy and following corticosterone replacement in the ANA rats. These results suggest that corticosterone stimulates ethanol intake in animals with pronounced high preference for ethanol.

The dynorphin and enkephalin systems in alcohol-preferring (AA) and alcohol-avoiding (ANA) rats

The dynorphin and enkephalin systems in alcohol-preferring (AA) and alcohol-avoiding (ANA) rats

Differences between Alcohol‐Preferring (AA) and Alcohol‐Avoiding (ANA) Rats in the Prodynorphin and Proenkephalin Systems

The motivation to drink alcohol and the eventual risk of becoming addicted are in part genetically determined. Because opioid peptides are considered central to motivated behaviors, we have analyzed opioid peptides in relevant areas of the brain of two outbred lines of rats: the alcohol-preferring [Alko Alcohol (AA)] line who voluntarily drink alcohol and the alcohol-avoiding [Alko Non-Alcohol (ANA)] line with negligible intake. (Met)enkephalinArg6Phe7 (MEAP) was measured as a marker of proenkephalin, and dynorphin A, dynorphin B, and (Leu)enkephalinArg6 as markers of the prodynorphin system. The major line differences and effects of alcohol intake were observed in mesolimbic brain areas. The mesolimbic dopamine pathway, which projects from the ventral tegmental area (VTA) to the nucleus accumbens, is central in the reward system. Basal levels of MEAP and dynorphin peptides were low in the nucleus accumbens of AA rats, whereas (Leu)enkephalinArg6 levels were lower in the VTA of these rats. Alcohol drinking caused MEAP levels in the accumbens to rise, but had no effect on prodynorphin peptides. Opioids also influence the nigrostriatal dopamine pathway. However, this study showed no significant differences for any peptide between rat lines, or effect of alcohol intake, in either substantia nigra or striatum, except for a decrease of nigral and striatal (Leu)enkephalinArg6 levels in alcohol-drinking AA rats. Large line differences were observed in the pituitary gland. AA rats had high basal levels of MEAP, which became even higher after voluntary alcohol consumption for 4 weeks, and low levels of dynorphin peptides, not affected by alcohol drinking.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in dopamine metabolism by intraperitoneal ethanol in rats selected for high and low ethanol preference: A 3-methoxytyramine study

Effects of an ethanol dose (1 g/kg, IP) on the metabolism of dopamine (DA) in the nucleus accumbens, striatum and hypothalamus of ethanol-naive alcohol-preferring (AA) and alcohol-avoiding (ANA) rats were studied. Rats were sacrificed by focused-beam microwave irradiation of the brain 20 minutes after ethanol administration, and the concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), assumed to reflect DA metabolism, and of 3-methoxytyramine (3-MT), assumed to reflect DA release, were measured using gas chromatography-mass spectrometry. Basal striatal DOPAC and HVA concentrations were higher in the AA rats in comparison with ANA rats. Ethanol increased HVA, but not DOPAC, concentration in the nucleus accumbens and striatum, but not in the hypothalamus. There was a significant rat line × ethanol treatment interaction with respect to HVA concentration in the nucleus accumbens. The increase in HVA was higher in the AA than ANA rats. Basal 3-MT concentration was not changed by ethanol, except in the nucleus accumbens, where a significant rat line × ethanol treatment interaction was found. A decrease in 3-MT concentration was only detected in the ANA rats. After inhibition of monoamine oxidase with pargyline hydrochloride (75 mg/kg, IP, 10 min before sacrifice), 3-MT accumulation was decreased by ethanol, especially in the nucleus accumbens of both AA and ANA rat lines as well as in that of nonselected Wistar rats. The results suggest that 1) DA metabolism to DOPAC and HVA is dissociable from DA release as reflected by 3-MT production, 2) ethanol, if anything, reduces DA release, and that 3) the AA and ANA rats differ in their basal DA metabolism and in the ethanol effects thereupon, but not in ethanol-induced changes in DA release.

Audiogenic immobility reaction and open-field behavior in AA and ANA rat lines

Individual predispositions in emotional reactivity have been suggested as factors involved in the development of alcoholism. To approach this problem, we assessed emotional reactivity in alcohol-naive animals from the alcohol-preferring (AA) and alcohol-avoiding (ANA) rat lines of Alko Ltd. AA rats are known to have higher brain levels of 5-hydroxytryptamine (5-HT) than ANA rats. Emotional reactivity was therefore assessed by an audiogenic immobility reaction (freezing), which is specifically sensitive to and shortened by depletion of 5-HT. The results showed that AA rats of both sexes displayed increased immobility reactions compared to the corresponding sex of the ANA rats. During the period of adaptation to the test cage ANA rats of both sexes showed increased locomotor activity compared to the corresponding sex of the AA rats. Levels of plasma corticosterone did not differ between the rat lines, either during resting or stressful conditions. The present results suggest that a passive, inhibited style of defensive behavior is associated with a high alcohol consumption.

Dietary regulation of voluntary alcohol consumption in rats: Influence of a high protein diet and a methylene blue diet

The importance of glucose homeostatis for high voluntary alcohol consumption was studied in alcohol-preferring (AA) and alcohol-avoiding (ANA) rats fed either a control diet, a protein-rich diet or a control diet supplemented with methylene blue. AA rats on the control diet were found to receive 13.6% of their daily energy intake from alcohol. On the high-protein or methylène blue diet, the alcohol consumption of the AA rats was respectively 40% and 48% higher than on the control diet. The voluntary alcohol consumption of ANA rats corresponded to 0.8–2.3% of their daily energy intake irrespective of diet. The protein diet increased the blood glucose concentration of AA rats by 20% but no increase was observed after the methylene blue diet. The diets had no effect on the blood glucose levels of ANA rats. In AA rats, the protein diet reduced the hepatic concentration of the three major glucogenic amino acids (serine, glycine, alanine) on average by 24%, suggesting an increased utilization for gluconeogenesis. No such reduction was observed in AA rats on the methylene blue diet or in ANA rats on any diet. The utilization of amino acids for maintenance of glucose balance in AA rats is further supported by the observed negative correlation between plasma concentration of urea, the end product of amino acid catabolism, and the sum of the concentrations of the three glucogenic amino acids in the liver, and by the positive correlation between plasma urea and blood glucose concentration. Furthermore, in AA rats, but not in ANA rats, the concentration of alanine, the main amino acid used in gluconeogenesis, correlated negatively with the amount of alcohol consumed. These findings indicate that the maintenance of glucose homeostatis is important for high voluntary alcohol consumption.

Characteristics of ethanol tolerance in alcohol drinking (AA) and alcohol avoiding (ANA) rats.

The development of tolerance to ethanol was examined in two rat lines selected for high (AA) and low (ANA) ethanol consumption. In the first experiment, the acquisition of tolerance to the motor-impairment, hypothermic and hypnotic effects of ethanol produced by daily treatment with 5 g/kg ethanol for a period of 24 days was examined. Tolerance to these effects of ethanol was observed in the AA rats while marginal or no tolerance was demonstrated in the ANA rats. In the second experiment the development of rapid tolerance to the hypothermic and hypnotic effects of ethanol was examined. The hypothermic and hypnotic responses to IP injection of 3.5 g/kg ethanol were found to be attenuated in the AA but not the ANA rats by a single equivalent ethanol injection given 24 h earlier. These results suggest some relationship between the capacity to develop tolerance and voluntary ethanol intake.

EFFECT OF PRENATAL ALCOHOL EXPOSURE ON NEONATAL SLEEP-WAKE BEHAVIOUR AND ADULT ALCOHOL CONSUMPTION IN THE AA AND ANA RAT LINES

To study the role of genetic factors in the effects of prenatal alcohol exposure on behaviour, dams of two rat lines developed to differ in voluntary alcohol intake, alcohol-preferring (AA) and alcohol-avoiding (ANA) rats were given a 5-10% alcohol solution mixed with a 1% sucrose solution as a sole drinking liquid throughout gestation. Sleep-wake behaviour of the offspring was studied at the ages of 7, 14 and 20 days, using a movement-sensitive mattress. In ANA rats, sleep recordings showed that prenatal alcohol exposure increased the percentage of waking but decreased the percentage of active sleep. Sleep-wake behaviour of the AA rats was not affected by alcohol exposure in utero. Prenatal alcohol exposure did not change open field behaviour in 1 month old rats, except that the alcohol-exposed AA rats' defaecation was decreased. When rats were 3 months old, voluntary intake of 10% (v/v) alcohol increased for alcohol-exposed ANA rats and decreased for alcohol-exposed AA rats as compared to the controls. The results indicate that AA rats may compensate for the effects of prenatal alcohol exposure on behaviour, whereas offspring of the alcohol-exposed ANA dams suffer from severe behavioural disturbances. These findings further suggest that genetic factors are responsible for the differences in the susceptibility of rat foetuses to alcohol-induced long-term effects on behaviour.

Electrolyte excretion in alcohol preferring and alcohol avoiding rats

Water and electrolyte metabolism was studied in alcohol preferring (AA) and alcohol avoiding (ANA) rats. During water diuresis AA rats had higher Mg, cAMP, creatinine and inorganic phosphate excretion, but lower urine and urinary protein output. During ethanol diuresis AA rats had lower Na, K, Ca, protein and urine output, but higher cAMP and inorganic phosphate excretion. Ethanol increased K, Ca and urine output in ANA rats only. A slight increase of blood pH was observed only in AA rats. Before ethanol ANA rats had higher plasma Ca concentration. Plasma aldosterone level was higher in AA rats. High salt excretion of ANA rats may lead them to prefer salt containing energy sources and therefore to avoid ethanol. On the other hand, renal salt conservation in AA rats may lead them to prefer ethanol.