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It has been suggested that some of the behavioral effects produced by ethanol are mediated by its first metabolite, acetaldehyde. The present research addressed the hypothesis that catalase-dependent metabolism of ethanol to acetaldehyde in the brain is an important step in the production of ethanol-related affective properties. Firstly, we investigated the contribution of brain catalase in the acquisition of ethanol-induced conditioned place preference (CPP). Secondly, the specificity of the catalase inhibitor 3-amino-1,2,4-triazole (AT) was evaluated with morphine- and cocaine-induced CPP. Finally, to investigate the role of catalase in the process of relapse to ethanol seeking caused by re-exposure to ethanol, after an initial conditioning and extinction, mice were primed with saline and ethanol or AT and ethanol and tested for reinstatement of CPP. Conditioned place preference was blocked in animals treated with AT and ethanol. Morphine and cocaine CPP were unaffected by AT treatment. However, the reinstatement of place preference was not modified by catalase inhibition. Taken together, the results of the present study indicate that the brain catalase-H(2)O(2) system contributes to the acquisition of affective-dependent learning induced by ethanol, and support the involvement of centrally-formed acetaldehyde in the formation of positive affective memories produced by ethanol.

The C57BL/6J strain of inbred mice shows a characteristic pattern of ethanol-induced behaviors: very weak acute locomotor stimulation, a lack of locomotor-sensitizing effect of ethanol, and a high level of ethanol intake. This strain has relatively low levels of activity of the ethanol metabolizing enzyme catalase, and it has been proposed that brain catalase plays a role in the modulation of some behavioral effects of ethanol. In the first study of the present paper, we investigated the effects of pharmacological manipulations of brain catalase activity on C57BL/6J mice in acute ethanol-induced locomotion and ethanol intake. Results indicated that the reduction in motor activity produced by ethanol was reversed by pretreatment with catalase potentiators and it was enhanced by catalase inhibitors. In addition, ethanol intake was highly correlated with brain catalase activity in mice treated with a catalase potentiator. In the second study, F1 hybrid mice (SWXB6) from the outbred Swiss-Webster mice and the inbred C57BL/6J mice were used. Basal brain catalase activity levels of F1 mice were intermediate between to those of the two progenitor genotypes. That profile of catalase activity was parallel to the acute-ethanol-induced locomotion and to repeated-ethanol-induced motor sensitization effects observed across the three types of mice. These data suggest that brain catalase activity modifications in the C57BL/6J strain change the pattern of several ethanol-related behaviors in this inbred mouse.

Anabolic-androgenic steroids are synthetic derivatives of testosterone, which are increasingly abused by adolescent populations who also abuse psychoactive substances. All these compounds lead to complex behavioral syndromes and the effects of their interactions remain unclear. The main aim of the present study was to determine the influence of testosterone on the locomotor activity-promoting effect of cocaine on male mice in an open field. In the three experiments, animals received two injections: firstly, testosterone or peanut oil, and secondly, cocaine or saline solution. In Experiments 1 and 2, testosterone (or oil) and cocaine (or saline) were injected 45 and 10 min, respectively, prior to activity recording. In the first experiment, we studied the effects of testosterone (2 mg/kg) on locomotor activity induced by different doses of cocaine (2, 4, 8, 10 or 12 mg/kg). In Experiment 2, we explored the effects of supraphysiological doses of testosterone (2, 6, 10 or 14 mg/kg) on animals treated with 10 mg/kg cocaine. Finally, in the third experiment, 14 mg/kg testosterone or vehicle was administered 15, 30, 45 or 75 min before activity data collection to animals that received 10 mg/kg cocaine or saline. Testosterone itself had no effects on spontaneous locomotor activity and, as was expected, cocaine increased locomotor activity dose-dependently. Given together, testosterone enhanced the cocaine-induced hyperactivity although not dose-dependently, the highest effects being found 45 min after testosterone injection. The present study confirmed the existence of an interaction between testosterone and cocaine at the central nervous system.

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.

It has been demonstrated that acute administration of lead to mice enhances brain catalase activity and ethanol-induced locomotion. These effects of lead seem to be related, since they show similar time courses and occur at similar doses. In the present study, in an attempt to further evaluate the relation between brain catalase activity and lead-induced changes in ethanol-stimulated locomotion, the interaction between lead acetate and 3-amino-1H,2,4-triazole (AT), a well-known catalase inhibitor, was assessed. In this study, lead acetate or saline was acutely injected intraperitoneally to Swiss mice at doses of 50 or 100 mg/kg 7 days before testing. On the test day, animals received an intraperitoneal injection of AT (0, 10, or 500 mg/kg). Five hours following AT treatment, ethanol (0.0 or 2.5 g/kg, ip) was injected and the animals were placed in open-field chambers, in which locomotion was measured for 10 min. Neither lead exposure nor AT administration, either alone or in combination, had any effect on spontaneous locomotor activity. AT treatment reduced ethanol-induced locomotion as well as brain catalase activity. On the other hand, ambulation and brain catalase activity were significantly increased by both doses of lead. Furthermore, AT significantly reduced the potentiation produced by lead acetate on brain catalase and on ethanol-induced locomotor activity in a dose-dependent manner. A significant correlation was found between locomotion and catalase activity across all test conditions. The results show that brain catalase activity is involved in the effects of lead acetate on ethanol-induced locomotion in mice. Thus, this study confirms the notion that brain catalase provides the molecular basis for understanding some of the mechanisms of the action of ethanol in the central nervous system.

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 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.

Homogenates of perfused rat brains incubated in the presence of ethanol (50-100 mM) and glucose (10 mM) were found to oxidize ethanol to acetaldehyde. The addition of glucose oxidase, a known hydrogen peroxide generator, to the incubation medium, significantly (P less than 0.05) increased the generation of acetaldehyde. The presence in the incubation medium of metyrapone, an inhibitor of cytochrome P450, or pyrazole, an alcohol dehydrogenase inhibitor, did not affect the levels of acetaldehyde obtained. Conversely, the presence of 3-amino-1,2,4-triazole, a known catalase inhibitor, induced a concentration-dependent reduction of the amount of acetaldehyde generated after incubation, even in the presence of glucose oxidase. Homogenates of perfused brains of rats treated with 3-amino-1,2,4-triazole or cyanamide (another H2O2-dependent catalase blocker) also showed a dose-dependent reduction of the acetaldehyde obtained. These findings support the notion that a catalase-mediated oxidation of ethanol is present in rat brain homogenates. It is suggested that this local oxidation of ethanol may have important biological implications. The data of both studies increase support for the notion that acetaldehyde is produced directly in the brain and that it may be the agent mediating some of the psychopharmacological properties of ethanol and be one of the factors determining the propensity of an animal to voluntarily consume ethanol.

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 results presented in this study demonstrate a progressive inhibition of rat brain catalase activity by AT in vivo. Furthermore, the inhibition of brain catalase by AT demonstrates the presence of hydrogen peroxide in brain, since AT inhibits catalase in the presence of this compound. The rate of inhibition of catalase seems to be dependent upon the rate by which H2O2 is generated. A time course study showed slower onset of the inhibition of brain as compared to liver catalase, possibly reflecting tissue hydrogen peroxide levels or, alternatively, a rate-limiting penetration of AT into brain and into the catalase compartment. The presence of AT in brain was confirmed over the time period of the observed inhibition of brain catalase. Catalase inhibitors are of particular interest in the study of the physiological role of catalase. This study further supports the use of AT in investigations designed to further understand the role of brain catalase.

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 present experiment demonstrated that acute administration of ethanol appeared to have a biphasic effect on the accumulation of 3-methoxy-4-hydroxyphenylethylene glycol sulfate (MHPG-SO4) in rat brain. The magnitude of these alterations in MHPG-SO4 levels was also observed to be highly correlated with peripheral blood ethanol levels. Since levels of MHPG-SO4 are considered to be an index of noradrenergic activity, the findings suggest that ethanol may affect norepinephrine activity in a specific dose- and time-dependent manner. These results are discussed in reference to previous reports describing apparent divergent effects on norepinephrine. Possible mechanisms for the biphasic actions are also suggested.

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.

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.