Combined effects of aldehyde dehydrogenase variants and maternal mitochondrial genes on alcohol consumption

Two lines of rats bred to differ in their voluntary alcohol consumption — the alcohol-abstaining UChA rats and the alcohol-drinking UChB rats — differ in how effectively toxic acetaldehyde is removed during alcohol metabolism. UChB animals carry efficient variants of the aldehyde dehydrogenase 2 (ALDH2) genes and have active mitochondria, resulting in fast removal of acetaldehyde. UChA animals, in contrast, carry less efficient ALDH2 variants and less active mitochondria, which result in transient elevations of acetaldehyde levels after alcohol ingestion. Cross-breeding studies have demonstrated that the presence of active mitochondria inherited from UChB females can fully abolish the reduction of alcohol consumption associated with the presence of less efficient ALDH2 variants — a phenomenon known as epistasis. These and other findings suggest that mitochondrial activity during alcohol metabolism should be considered a new modulator of alcohol consumption not only in rats but also in other species, including humans

Effect of concurrent saccharin intake on ethanol consumption by high-alcohol-drinking (UChB) rats

This study examined the effect of concurrent presentation of a highly palatable saccharin solution on ethanol consumption during the acquisition or maintenance of ethanol drinking by high-alcohol-drinking (UChB) rats. Rats were exposed to ethanol (10% v/v) and water under a home cage, two-bottle, free-choice regimen with unlimited access for 24 hours/day. After 7 days (acquisition) of ethanol exposure, a third bottle containing saccharin (0.2% w/v) was concomitantly offered for an additional seven consecutive days, and the same process was repeated after 3 months (maintenance) of ethanol exposure. We found that concurrent saccharin intake significantly reduced ethanol intake by UChB rats after 7 days of ethanol exposure indicating that preference for sweet taste tends to override the preference for ethanol. However, the concurrent saccharin presentation to rats after 3 months of stable ethanol consumption did not reduce ethanol intake, whereas their saccharin consumption reached polyd

Effect of captopril on voluntary consumption of ethanol, water and solid food by UChA and UChB rats

Angiotensin converting enzyme inhibitors (ACEI) have been reported to reduce ethanol consumption in rats, but it is unclear whether this effect is specific for ethanol or secondary to effects on appetite or satiation for calories or water. In the present study we assessed the effect of captopril, an ACEI, on the voluntary consumption of 10% ethanol solution, water and solid food in our strain of rats genetically selected for their voluntary consumption of ethanol, namely UChA (low consumer) and UChB (high consumer). Captopril (30 mg/kg) was injected intraperitoneally for 3 consecutive days to UChA and UChB rats and ethanol, water and food intake were measured before, during and after captopril treatment; these results were compared with those produced by a control saline solution. Results showed that captopril produced a significant reduction of alcohol voluntary consumption in UChB but not in UChA rats. However, this effect was not specific for ethanol since captopril also induced a

Effect of a dose of ethanol on acute tolerance and ethanol consumption in alcohol drinker(UChB) and non-drinker (UChA) rats

Acute tolerance that develops within minutes of ethanol exposure appears to influence the apparent acute behavioral sensitivity of laboratory animals to ethanol actions. The existence of a correlation between voluntary ethanol consumption and the speed of acquiring acute tolerance has been proposed. In the present paper we investigated the effect of an acute dose of ethanol on tolerance development and on ethanol voluntary consumption in our two selected bred strains, UChA (low ethanol drinker) and UChB (high ethanol drinker) rats. Acute tolerance developed to motor impairment induced by a dose of ethanol of 2.3g/kg. administered intraperitoneally was evaluated by the tilting plane test. Voluntary ethanol consumption was compared in rats receiving the ethanol dose, to rats receiving a saline intraperitoneal (i.p.) injection. The results show that UChB rats receiving an intoxicating dose of ethanol develop more tolerance and they significantly increased their ethanol consumption compar

Ethanol intake: Effect on liver and brain mitochondrial function and acetaldehyde oxidation

The effect of a chronic ethanol consumption by forcing rats to drink a 20% v/v ethanol solution as sole drinking fluid, for 3 months, was evaluated on: liver and brain mitochondrial function, the capacity of isolated mitochondria to oxidize acetaldehyde, as well as on the low Km mitochondrial AlDH activity, in rats. The O2 uptake by liver and brain mitochondria in the presence of glutamate + malate, succinate or ascorbate + TMPD, was measured polarographically with a Clark electrode. Acetaldehyde oxidation was measured by the disappearance rate in presence of the intact or disrupted mitochondria (AlDH activity) by gas chromatography. Results indicate that an ethanol intake of 11 g/kg b.wt. per day produce a significant reduction of the liver mitochondrial respiration tested with all the substrates used, including acetaldehyde. In contrast, the activity of AlDH in disrupted mitochondria remained unchanged. These results are in accord with the idea that a progressive deterioration of li

Sensitivity of Liver Mitochondrial Functions to Various Levels of Ethanol Intake in the Rat

Mitochondrial function appears to be an early target for ethanol toxicity, however it is not clear to what extent the effects of ethanol, which occur at levels of intake lower than those already reported in the literature, can induce an alteration of it. To produce different levels of ethanol intake, the spontaneous consumption of ethanol by genetically low (UChA) and genetically high (UChB) rats, as well as the forced intake obtained by offering 10% v/v ethanol solution as the only source of drinking fluid, were employed. The O2 uptake by liver mitochondria of rats submitted to these conditions in the presence of glutamate + malate, succinate or ascorbate + TMPD, was measured polarographically with a Clark electrode at 25°C. Results indicate that alterations of the hepatic mitochondrial function can be detected at levels of ethanol intake much lower than those previously reported. Whereas, a level of a daily ethanol intake of 2–3 g/kg body weight in UChA rats under free choice was in

Acetaldehyde metabolism by brain mitochondria from UChA and UChB rats

The acetaldehyde (AcH) oxidizing capacity of total brain homogenates from the genetically high-ethanol consumer (UChB) appeared to be greater than that of the low-ethanol consumer (UChA) rats. To gain further information about this strain difference, the activity of aldehyde dehydrogenase (AIDH) in different subcellular fractions of whole brain homogenates from naive UChA and UChB rat strains of both sexes has been studied by measuring the rate of AcH disappearance and by following the reduction of NAD to NADH. The results demonstrated that the higher capacity of brain homogenates from UChB rats to oxidize AcH when compared to UChA ones was because the UChB mitochondrial low Km AIDH exhibits a much greater affinity for NAD than that of the UChA rats, as evidenced by four- to fivefold differences in the Km values for NAD. But the dehydrogenases from both strains exhibited a similar maximum rate at saturating NAD concentrations. Because intact brain mitochondria isolated from UChB rats

Effect of diet and disulfiram on acetaldehyde blood levels after ethanol in UChA and UChB rats

Acetaldehyde (AcH) levels in blood samples taken from different zones of the vascular system 2 h after a p.o. dose of ethanol (2.76 g/kg) were studied in UChA (low ethanol consumer) and UChB (high ethanol consumer) rats fed a diet devoid of animal products, diet 1 (D1), and a diet containing fish meal, diet 2 (D2), and in rats pretreated with disulfiram (600 mg/kg p.o.). The results showed that, while there is no significant difference between UChA and UChB rats fed D1 with respect to blood AcH levels and the basal activity of the hepatic mitochondrial high-affinity aldehyde dehydrogenase (AlDH), a significant strain difference was observed in rats fed D2, which induced high blood AcH levels in UChA rats but not in UChB ones. No strain differences were observed in blood ethanol levels in the two groups of rats. When rats fed D1 were pretreated with disulfiram, the raising of AcH blood levels induced by ethanol after disulfiram was significantly higher in UChA than in UChB rats in supr

Investigations on the ethanol-induced flushing reaction: effects of propranolol and dipyridamole on acetaldehyde and prostacyclin metabolism

Disulfiram, an aldehyde dehydrogenase (ALDH) inhibitor, induces a flushing reaction upon the ingestion of ethanol, exerting aversion against alcohol that has been used in the treatment of alcoholism. This unpleasant response has been associated with an accumulation of acetaldehyde, and more recently, with an increase in vascular prostacyclin (PGI2) production. To evaluate the possibility of evoking the flushing reaction with drugs less toxic than disulfiram, we studied the effects of propanolol and dipyridamole on ALDH and PGI2. Acetaldehyde oxidation rate was assessed by gas chromatography in mitochondria from rats treated with these drugs for seven days. Prostacyclin generation was determined in rat aortic rings incubated in Krebs-Ringer with these drugs separately and associated to acetaldehyde, and measured by radioimmunoassay of 6-keto-PGFaα. Propanolol inhibited acetaldehyde oxidation rate whereas dipyridamole did not. Furthermore, propanolol increased blood acetaldehyde levels

Baclofen reduces ethanol intake in high-alcohol-drinking University of Chile bibulous rats

Treatment with γ-aminobutiric acid (GABAB) receptor agonist, ±baclofen, has been shown to reduce ethanol intake in selectively bred Sardinian alcohol-preferring rats. The general goal of the present study was to characterize the high ethanol consumption high-alcohol-drinking University of Chile bibulous (UChB) rats with regard to the anti-alcohol effect of GABAB receptor stimulation. UChB rats were treated with the more active enantiomer of baclofen [R(+)-baclofen; at a dose of 1.0, 2.0 or 3.0 mg/kg] administered intraperitoneally once daily for four consecutive days or a single dose. When comparing ethanol and saccharin consumption in a free-choice regimen with unlimited access 24 hours/day, the dose of baclofen required to attenuate ethanol consumption significantly was 1.0 mg/kg administered once a day for three consecutive days while the dose that was sufficient to affect saccharin consumption significantly was 2.0 mg/kg, indicating that baclofen was more potent in reducing ethano