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The present study deals with the effect of L-cysteine on the acute stimulating effects of ethanol. Swiss albino mice were pretreated with 0.0, 18.75, 37.50, or 75.00 mg/kg of cysteine simultaneously, 30 or 60 min, before the administration of saline or 0.8, 1.6, 2.4, or 3.2 g/kg of ethanol at 20% vol./vol. After these treatments, mice were left in the open-field chamber for 20 min, and locomotor activity was evaluated for the last 10 min. The specificity of the effects of L-cysteine was analyzed with the use of two drugs that also induce locomotor activity--d-amphetamine and methanol. Mice received L-cysteine (37.5 mg/kg), and 30 min after this treatment d-amphetamine (2 mg/kg) or methanol (2.4 g/kg) was injected. Data showed that L-cysteine at 37.5 mg/kg was able to increase locomotion induced by 2.4 and 3.2 g/kg of ethanol when it was administered 30 min before ethanol injection. The effects of L-cysteine are specific for the stimulation of ethanol on locomotion, because L-cysteine does not alter d-amphetamine-induced locomotor activity or methanol-induced locomotion. Moreover, blood ethanol levels were not affected by L-cysteine pretreatment. Therefore, the present findings demonstrated that ethanol-induced locomotor effects are enhanced by L-cysteine, in a manner similar to that of other sulfur amino acids.

The involvement of brain catalase in modulating the psychopharmacological effects of ethanol was investigated by examining ethanol-induced locomotor activity in sodium azide-treated mice. Mice were pretreated with i.p. injections of the catalase inhibitor sodium azide (5, 10, or 15 mg/kg) or saline. Following this treatment, animals received i.p. injections of ethanol (0.0, 1.6, 2.4, or 3.2 g/kg). Ten minutes after ethanol administration, locomotor activity was recorded during a 10-min testing period in open-field chambers. The time effect between the two treatments (0, 30, 60, or 90 min) was also evaluated. Results indicated that sodium azide alone did not change spontaneous locomotor activity. However, this catalase inhibitor significantly reduced ethanol-induced locomotor activity when it was injected simultaneously or 30 min before ethanol injections. Moreover, perfused brain homogenates of mice treated with sodium azide also showed a significant reduction of catalase activity. No differences in blood ethanol levels were observed between sodium azide and saline pretreated animals. Results of an additional experiment showed that sodium azide (10 mg/kg, at 30 min) did not produce an effect on d-amphetamine- (2 mg/kg) or tert-butanol- (0.5 g/kg) induced locomotor activities. A specific interaction between ethanol and sodium azide at the level of the central nervous system is suggested. These results provide further support for the involvement of brain catalase in ethanol-induced behavioral effects. They also support the notion that acetaldehyde may be produced directly in the brain by catalase and that it may be an important regulator of ethanol's locomotor effects.

Several reports have demonstrated that chronic lead administration decreases brain catalase activity in animals. Other reports have shown a role of brain catalase on ethanol-induced behaviors. In the present study, we questioned whether mice treated chronically with lead, and therefore functionally devoid of brain catalase activity, exhibit some alterations in ethanol-induced behaviors. Swiss-Webster mice were exposed to drinking fluid containing either 500 ppm lead acetate or sodium acetate (control group) for 0, 15, 30, or 60 days before an acute ethanol administration. Following ethanol injection (2.5 g/kg, i.p.), animals were placed in open field chambers and locomotor activity was measured. Lead exposure had no effect on spontaneous locomotor activity. However, a reduction in ethanol-induced locomotor activity was found at all periods of lead exposure. After 60 days of treatment, the lead group demonstrated 35% less activity than the control group. Brain catalase activity was significantly reduced in the lead group following 60 days of exposure. This reduction in ethanol-induced locomotor activity and in brain catalase activity persisted after 40 days of lead withdrawal. The fact that brain catalase and ethanol-induced locomotor activity followed a similar pattern could suggest a relationship between both lead acetate effects and also a role for brain catalase in ethanol-induced behaviors.

The role of brain catalase in modulating the psychopharmacological effects of ethanol was investigated by examining ethanol induced motor activity in normal, C3H-N, and a corresponding group of acatalasemic C3H-A, mice. Following administration of one of three doses of ethanol (0.8, 1.6, and 3.2 g/kg) or saline, mice were placed in open field chambers and locomotor and rearing activity was measured during a 10-min testing period. A significant increase in locomotor activity was recorded in both groups of mice at lower doses of ethanol, while the higher dose produced a marked depression. Normal mice demonstrated more locomotor activity than acatalasemic mice at all ethanol doses. No differences between both groups of mice were observed in rearing activity. Also, no differences in blood ethanol levels were observed between the two substrains. Brain and liver residual catalase activity in the acatalasemic mice was found to be 40% and 50%, respectively, of normal mice. Furthermore, evidence for possible involvement of the peroxidatic activity in ethanol-induced motor activity is presented. These results suggest a role for centrally formed acetaldehyde as a factor mediating some of ethanol's psychopharmacological effects.

The effect of a centrally acting noradrenergic agonist on voluntary ethanol intake was investigated in the laboratory rat. Doses of 1.5, 7.5, 15 and 25 mg/kg of FLA-136 were administered to animals chronically exposed to ethanol on a free choice basis. Administration of the highest dose of the drug brought about a 40% reduction in voluntary ethanol intake with no significant effect on total fluid consumption. These results would seem to indicate a possible functional relationship between rate of norepinephrine turnover and amounts of ethanol voluntarily consumed by the laboratory rat.

The possible existence of a biological marker system mediating voluntary consumption of ethanol in rats has been examined in a series of studies. The working hypothesis underlying this research was that acetaldehyde, the primary metabolite of ethanol, mediates the positive reinforcing properties of ethanol and thus underlies the voluntary consumption of ethanol in both animals and humans. We further hypothesized that brain catalase and aldehyde dehydrogenase, the enzymes controlling the production and elimination of acetaldehyde in the brain, may represent a biological marker system underlying the affinity of the animals to consume ethanol. Data demonstrating that the activity levels of these enzymes are positively correlated with alcohol ingestion seems to suggest that it is likely that the enzyme activity can serve as a predictor of the propensity to drink alcohol. A predictive model is proposed which describes the modulation of voluntary ethanol intake through the activity of these enzymes and their role in determining rates of formation and degradation of acetaldehyde in the brain.

The relationship between voluntary ethanol consumption and brain catalase activity was investigated in male Long Evans rats. In the first study, rats which were voluntarily consuming alcohol or water for 25 days were sacrificed by decapitation immediately (group A) or 15 days (group B) following withdrawal of alcohol and their brains analysed for catalase activity. Mean brain catalase activity did not differ among the two groups of rats exposed to ethanol and the ones exposed to water only. Furthermore, there were significant positive correlations between individual voluntary ethanol intake and catalase activity in both groups, (group A:r = .69, p less than or equal to 0.05; group B:r = .54, p less than or equal to 0.05). In the second study, rats were forced to drink high levels of ethanol presented as the only source of fluid for 25 days. Rats were sacrificed and brain, liver, muscle and heart tissue were extracted and analysed for catalase activity. There were no differences in mean brain catalase activity between water and forced ethanol drinking rats indicating that the enzyme was not inducible by high volume ethanol consumption. The results suggest that inherent differences in brain catalase activity may be one of the factors in determining an animal's propensity to voluntarily consume ethanol.

The relationship between voluntary ethanol intake and brain aldehyde dehydrogenase (ALDH) activity was investigated in the laboratory rat. Voluntary ethanol intake was compared to subcellular forms of brain ALDH. Mitochondrial, microsomal and cytosolic fractions were prepared and recovered ALDH activity of each form was compared to voluntary ethanol intake in Long Evans rats. Strong correlations were found between both mitochondrial and microsomal ALDH fractions and ethanol intake. No activity was observed in cytosolic fraction as measured with aromatic or aliphatic aldehydes. In addition, microsomal activity was detected with aromatic aldehydes only, whereas the mitochondrial form would oxidize both aromatic and aliphatic aldehydes.