The effect of cyanamide and 4-methylpyrazole on the ethanol-induced locomotor activity in mice

To assess the role of cyanamide and 4-methylpyrazole (4-MP) in mediating ethanol-induced locomotor activity in mice, they were pretreated with cyanamide (12.5, 25, or 50 g/kg) prior to one ethanol injection (2.4 g/kg) and showed significantly depressed locomotor activity compared with control groups. Cyanamide (25 mg/kg) also cancelled out the biphasic action of ethanol (0, 0.8, 1.6, 2.4, 3.2, or 4 g/kg) on locomotor activity. The action of cyanamide and 4-MP in combined administration was also tested. Our data show that pretreatment with 4-MP alone does not change the spontaneous or ethanol-induced locomotor activity. Conversely, when mice were pretreated with cyanamide and 4-MP, the depressive effect of cyanamide on the locomotor activity induced by ethanol disappeared, and the locomotor activity rose to levels similar to those of the control group, recovering the biphasic ethanol effect. These effects cannot be attributed to peripheral elevated blood acetaldehyde levels, as pretreatment with 4-MP prevents accumulation of acetaldehyde. These data might suggest some influence of brain catalase and aldehyde dehydrogenase (ALDH) on the effects of ethanol.     

Concurrent administration of diethyldithiocarbamate and 4-methylpyrazole enhances ethanol-induced locomotor activity: the role of brain ALDH

RATIONALE: It has been proposed that brain aldehyde dehydrogenase (ALDH) plays a role in the modulation of some psychopharmacological effects of ethanol. Diethyldithiocarbamate (DDTC), an ALDH inhibitor, elevates blood acetaldehyde levels in the presence of ethanol. Concurrent administration with 4-methylpyrazole (4-MP), an alcohol dehydrogenase inhibitor, prevents peripheral accumulation of acetaldehyde by DDTC. OBJECTIVE: To investigate the effects of concurrent DDTC and 4-MP administration on ethanol-induced locomotor activity in mice. METHODS: Mice were pretreated IP with saline (S+S) or 4-MP (10 mg/kg) (S+4-MP), then received IP injections of ethanol (0, 0.8, 1.6, 2.4, 3.2 and 4 g/kg) prior to testing in the open field. RESULTS: Pretreatment with 4-MP does not modify the spontaneous or ethanol-induced locomotor activity. In the second experiment, the DDTC (114, 228 and 456 mg/kg) and 4-MP (DDTC+4-MP) were administered 8 h prior to testing locomotor activity in the open field. Animals were then treated with ethanol (0, 0.8, 1.6, 2.4, 3.2 and 4 g/kg), and placed in open field chambers. The locomotor activity of animals pretreated with DDTC and 4-MP was significantly enhanced here compared to groups S+S and S+4-MP. These effects cannot be attributed to elevated blood acetaldehyde levels, as pretreatment with 4-MP prevented peripheral accumulation of acetaldehyde. CONCLUSIONS: These data suggest that brain ALDH may contribute to the effects of ethanol on locomotor activity. This role of the enzyme ALDH in some of the psychopharmacological effects of ethanol may be a result of its ability to regulate levels of acetaldehyde in brain.     

The metabolism of acetaldehyde and not acetaldehyde itself is responsible for in vivo ethanol-induced lipid peroxidation in rats

A single oral administration of ethanol (5 g/kg) to rats induced a marked increase in lipid peroxidation, in the liver and kidney within 9 hr, as assessed by malondialdehyde accumulation. The pretreatment with alcohol dehydrogenase (ADH) inhibitor, 4-methylpyrazole (1 mmol/kg) caused approximately 50% inhibition of the hepatic ADH activity and abolished this ethanol-induced lipid peroxidation. The disulfiram treatment (100 mg/kg) significantly inhibited 63% of the hepatic low Km aldehyde dehydrogenase (ALDH) but not the high Km ALDH. The cyanamide treatment (15 mg/kg) effectively decreased 83% of the low Km and 70% of the high Km ALDH in the liver. Although there was more than a 20-fold elevation of acetaldehyde levels by the inhibition of acetaldehyde metabolism with disulfiram or cyanamide, the ethanol-induced lipid peroxidation was significantly suppressed by pretreatment with these drugs. More than 90% inhibition of xanthine oxidase and dehydrogenase by the pretreatment with allopurinol (100 mg/kg), with no effect on the hepatic ADH and ALDH activities, did not alter the enhancement of lipid peroxidation following ethanol administration. We propose that the metabolism of acetaldehyde (probably via the low Km ALDH) and not acetaldehyde itself is responsible for the ethanol-induced lipid peroxidation in vivo and that the contribution of xanthine oxidase, as an initiator of lipid peroxidation through acetaldehyde oxidation is minute during acute intoxication.     

Effects of cyanamide and acetaldehyde accumulation on the locomotor stimulant and sedative effects of ethanol in mice

Ethanol administration induces both locomotor stimulant and sedative effects depending upon blood ethanol concentrations. Recent studies in rats and mice suggest that acetaldehyde, the first product of ethanol metabolism, might be involved in the expression of both the stimulant and the sedative effects of ethanol. A number of studies have used the drug cyanamide in an attempt to clarify the role of acetaldehyde in the behavioral effects of ethanol. The results of such studies are, however, difficult to interpret because cyanamide is an inhibitor of the enzymes catalase and aldehyde dehydrogenase, two enzymes with opposite effects on brain acetaldehyde concentrations. This study was aimed at clarifying the effects of cyanamide on ethanol-induced locomotor stimulant and sedative effects in Swiss mice. The locomotor stimulant effects of ethanol were measured in standard activity boxes, whereas the sedative effects of ethanol were quantified using the loss of righting reflex procedure. Cyanamide prevented the locomotor stimulant effects of 2 g/kg ethanol, although this was mainly due to a potentiation of the inhibitory effects of ethanol as evidenced by a prolongation of ethanol-induced loss of righting reflex. Additionally, 4-methylpyrazole, an inhibitor of the enzyme alcohol dehydrogenase, prevented these effects of cyanamide. It is concluded that in vivo the effects of cyanamide are predominantly due to the inhibition of the enzyme aldehyde dehydrogenase, rather than to its effects on catalase.     

Role of acetaldehyde in ethanol-induced conditioned taste aversion in rats

Rationale. In spite of many recent studies on the effects of acetaldehyde, it is still unclear whether acetaldehyde mediates the reinforcing and/or aversive effects of ethanol. Objectives. The present study reexamined the role of acetaldehyde in ethanol-induced conditioned taste aversion (CTA). A first experiment compared ethanol- and acetaldehyde-induced CTA. In a second experiment, cyanamide, an aldehyde dehydrogenase inhibitor, was administered before conditioning with either ethanol or acetaldehyde to investigate the effects of acetaldehyde accumulation. Methods. A classic CTA protocol was used to associate the taste of a saccharin solution with either ethanol or acetaldehyde injections. In experiment 1, saccharin consumption was followed by injections of either ethanol (0, 0.5, 1.0, 1.5 or 2.0 g/kg) or acetaldehyde (0, 100, 170 or 300 mg/kg). In experiment 2, the rats were pretreated with either saline or cyanamide (25 mg/kg) before conditioning with either ethanol or acetaldehyde. Results. Both ethanol and acetaldehyde induced significant CTA. However, ethanol produced a very strong CTA relative to acetaldehyde that induced only a weak CTA even at toxic doses. Cyanamide pretreatments significantly potentiated ethanol- but not acetaldehyde-induced CTA. Conclusions. The present results indicate that ethanol-induced CTA does not result from brain acetaldehyde effects. In contrast, it is suggested that the reinforcing effects of brain acetaldehyde might actually reduce ethanol-induced CTA. Our results also suggest that the inhibition of brain catalase activity may contribute to the potentiating effects of cyanamide on ethanol-induced CTA. Electronic Publication     

Blood acetaldehyde levels in alcohol-dosed rats after treatment with ANIT, ANTU, dithiocarbamate derivatives, or cyanamide

In adult female Wistar rats, pretreated by gavage with two doses - 16 or 256 mumol/kg - of cyanamide, TMTD (tetramethylthiuram disulfide), TMTM (tetramethylthiuram monosulfide), Ziram or Zineb at 90 min or 18 h before administration of 2 g of ethanol/kg i.p., the blood acetaldehyde levels were significantly increased for 90 - 240 min after ethanol administration (exceptions were noted after exposure to Zineb for 90 min or to low-dosed cyanamide for 18 h). After pretreatment for identical periods with ANTU (N-1-naphthylthiourea) or ANIT (1-naphthylisothiocyanate) at doses extending into the LD50 range, the blood acetaldehyde levels of rats given the same dose of ethanol remained uninfluenced. The increase in blood acetaldehyde recorded after 16 mumol/kg p.o. of TMTM and TMTD remained detectable for up to 48 h. Onset of the cyanamide action occurred already after 45 min. While recognizing that results from animal experiments cannot be transposed without restriction to the human situation, it is concluded that occupational contacts with ANTU or ANIT are not likely to elicit increased blood acetaldehyde levels in man after ingestion of alcohol. The risk of an ethanol intolerance reaction due to a rise in blood acetaldehyde therefore does not appear to be warranted. The present findings indicate, however, that exposure to TMTD, TMTM, Ziram, Zineb or cyanamide is associated with a definite health risk; because of the long persistence of these substances in the body, the risk exists for a long time post-exposure.     

The roles of the hepatocellular redox state and the hepatic acetaldehyde concentration in determining the ethanol elimination rate in fasted rats

Ethanol administration (2 g/kg i.p.) to fasted male Wistar rats caused, on average, a 64% decrease in the cytosolic free NAD+:NADH ratio and a 41% decrease in the mitochondrial free NAD+:NADH ratio measured 90 min after ethanol was injected. Treatment of animals with either Naloxone (2 mg/kg i.p.) 1 hr after ethanol or 3-palmitoyl-(+)-catechin (100 mg/kg p.o. 1 hr before ethanol) prevented these ethanol induced redox state changes, without affecting the ethanol elimination rate or the hepatic acetaldehyde concentration measured at 90 min after ethanol administration. The thiol compounds cysteine and malotilate (diisopropyl-1,3-dithiol-2-ylidene malonic acid) significantly lowered the hepatic acetaldehyde concentrations measured at 0.75, 1.5 and 6.0 hr after ethanol, and caused a 29% and 12% increase respectively in the ethanol elimination rate, without affecting the ethanol induced alterations in the NAD+:NADH ratio. Pretreatment of animals with the aldehyde dehydrogenase inhibitor, cyanamide (1 mg/kg or 15 mg/kg p.o. one hour before ethanol), caused increases of up to 23-fold in the hepatic acetaldehyde level, without influencing the cytosolic NAD+:NADH ratio in ethanol dosed rats, while significantly reducing the ethanol elimination rate by up to 44%, compared with controls. These results suggest that ethanol oxidation by cytosolic alcohol dehydrogenase may be regulated in part by the hepatic acetaldehyde concentration achieved during ethanol metabolism rather than NADH reoxidation, either to supply NAD for the dehydrogenase, or to reduce inhibition of the enzyme by NADH, being a rate-limiting factor in ethanol metabolism in fasted rats.     

Distribution of oral 4-methylpyrazole in the rat: inhibition of elimination by ethanol

4-Methylpyrazole (4-MP), a potent competitive inhibitor of alcohol dehydrogenase activity, is being studied as a therapeutic agent for methanol and ethylene glycol poisoning. In order to evaluate the distribution of 4-MP using doses in the potentially therapeutic range, male Sprague-Dawley rats were administered 4-MP orally at zero time in doses of 5, 10, or 20 mg/kg. Half of the rats were also treated orally at 0, 1, 2, and 3 h with ethanol (1 g/kg each h) and half with glucose in isocaloric amounts. At doses of 10 and 20 mg/kg, 4-MP elimination appeared to be saturated, with an elimination rate of 10 mumol/L/h. Elimination at 5 mg/kg was non-conclusive as to the order. The rate of 4-MP elimination was decreased about 50% by concomitant administration of ethanol. Urinary excretion of unchanged 4-MP accounted for only about 1% of the dose; the amount excreted unchanged was significantly increased by ethanol administration. The results demonstrate the mutual inhibition of metabolism by ethanol and 4-methylpyrazole, which may explain why the inhibition of ADH by 4-MP can be longer than that predicted by the elimination rate of 4-MP alone.     

Inhibition of acetaminophen hepatotoxicity by acetaldehyde in the rat.

Since we have observed that acetaldehyde, an oxidative metabolite of ethanol, inhibits acetaminophen activation in rat liver microsomes, the in vivo effect of acetaldehyde on acetaminophen hepatotoxicity was tested. In vivo experiments in 3-methylcholanthrene-pretreated male Sprague-Dawley rats showed that administration of cyanamide (20 mg/kg, i.p.) and acetaldehyde (600 mg/kg, s.c.) given 3 and 1 h, respectively, prior to acetaminophen (500 mg/kg, i.p.) but not cyanamide alone prevented acetaminophen hepatotoxicity as assessed by serum transaminases and histology. Acetaldehyde may partly be responsible for the inhibitory effect of ethanol on acetaminophen hepatotoxicity.     

Effect of 4-methylpyrazole and pyrazole on the induction of fatty liver by a single dose of ethanol

Pyrazole (272 mg/kg), 4-methylpyrazole (4-MP; 200 mg/kg) or saline was injected intraperitoneally into fasted male and female rats. Ten min later, ethanol (4 or 6 g/kg) or an equicaloric dose of sucrose was given by stomach tube. Hepatic triglyceride (TG) levels were measured at 6, 12 or 16 hr after the gavage. With a 4 g/kg dose of ethanol, pyrazole reduced the accumulation of TG at 6 hr in females, but not at 12 and 16 hr. In males, ethanol gave relatively little TG accumulation at 6 hr and pyrazole did not affect this, but at 16 hr the TG levels in the ethanol-pyrazole group had not risen as much as in the ethanol-saline group. In contrast to pyrazole, 4-MP by itself increased liver TG content, and significantly increased the TG accumulation caused by a 4 g/kg dose of ethanol in both males and females at 16 hr. However, 4-MP caused a significantly smaller TG accumulation in females at 6 hr after the ethanol, but not in males. With a larger dose of ethanol (6 g/kg), both pyrazole and 4-MP decreased the accumulation of TG at 16 hr in males. It is concluded that ethanol per se, ethanol as a metabolic substrate, and pyrazoles as pharmacological agents with complex actions may all contribute to the development of acute fatty liver. Therefore, pyrazole and 4-MP do not appear to be suitable tools for resolving the controversy about the mechanism of production of alcoholic fatty liver.     

Role of ethanol metabolism in the alcohol-induced increase in urinary folate excretion in rats

Chronic ethanol use can lead to folic acid deficiency in humans. In rats, acute doses of ethanol produce a marked increase in the urinary excretion of folate which is followed by a decrease in plasma folate levels. To assess the respective roles of ethanol and its metabolism in these effects, five groups of male Sprague-Dawley rats were treated orally as follows: (1) ethanol in four doses of 1 g/kg each at 0, 1, 2 and 3 hr; (2) ethanol as above plus the alcohol dehydrogenase inhibitor 4-methylpyrazole (4-MP) at 50 mg/kg, i.p., 15 min prior to 0 hr; (3) glucose in four isocaloric doses; (4) glucose plus 4-MP as above; and (5) methanol in four doses of 1 g/kg. Total folate levels in the urine peaked in both ethanol- and methanol-treated rats at the same time as the urine alcohol levels (after 6-8 hr) and then declined over the same time course as the alcohol levels. Concurrent administration of 4-MP inhibited the metabolism of ethanol and maintained the increase in urinary folate excretion throughout 24 hr. Ethanol administration produced minor changes in the relative distribution of folate derivatives in the urine, and these changes were not prevented by 4-MP treatment. The urinary levels of formic acid, which is metabolized by folate-dependent processes, were increased by ethanol administration; this increase was prevented by 4-MP. These results suggest that ethanol is not unique among alcohols in increasing urinary folate excretion and that ethanol metabolism plays no role in the increased urinary folate excretion. However, ethanol metabolism contributes to a second effect of ethanol on the folate system, which leads to increased urinary levels of formic acid.     

Endogenous acetaldehyde in rats. Effects of exogenous ethanol, pyrazole, cyanamide and disulfiram

Male Long-Evans rats consumed the alcohol and aldehyde dehydrogenase inhibitors pyrazole, cyanamide or disulfiram, for 6 days. No endogenous blood acetaldehyde could be detected in controls and pyrazole treated rats, endogenous blood concentrations up to 2-5 nmoles/ml were, however, measured in the cyanamide and disulfiram-treated animals. Other rats received daily ethanol gastric intubations in addition to the consumption of the inhibitors. Little or no acetaldehyde was detected in the controls and pyrazole treated animals during acute ethanol intoxication or on the subsequent days. High blood levels (200-500 nmoles/ml) were observed in the rats consuming cyanamide and disulfiram, and concentrations up to 10-12 nmoles/ml were still found on the following day after all the ethanol had been eliminated. This acetaldehyde and the endogenous acetaldehyde could only be observed with the hemolyzation method in which blood hemolyzates were directly heated prior to headspace GC analysis; none was detected if blood proteins were first precipitated and removed with perchloric acid. It is suggested that aldehyde dehydrogenase inhibitors elevate endogenous concentrations of bound acetaldehyde and that exogenous ethanol increases this form of acetaldehyde.     

Comparative effects of chronic ethanol and acetaldehyde exposure on myocardial function in rats

This study was conducted to compare separately the chronic effects of high blood levels of ethanol and acetaldehyde on the metabolism of the heart. Levels of ethanol and acetaldehyde were altered by administration of either 4-methylpyrazole (4-MP), a potent alcohol dehydrogenase inhibitor, or pargyline (PAR), a monoamine oxidase inhibitor that markedly increases acetaldehyde levels in the blood following ethanol administration. Measurements were made in rats consuming ethanol for three to four weeks. Mitochondrial respiration, in vitro contractility of glycerinated heart muscle fibers, and myocardial protein synthesis were determined. As compared to animals receiving only ethanol, administration of either-4-methyl-pyrazole or pargyline plus ethanol resulted in more severe damage to mitochondrial respiration and myocardial protein synthesis. The data illustrate that both acetaldehyde and ethanol in high concentrations can cause severe damage to myocardial metabolism.     

Demonstration of a functional blood-testis barrier to acetaldehyde. Evidence for lack of acetaldehyde effect on ethanol-induced depression of testosterone in vivo

In vitro studies have shown that acetaldehyde is a more potent inhibitor of testicular steroidogenesis than ethanol. The present study examined the in vivo role of acetaldehyde in ethanol-induced reduction of testosterone by (1) determining the levels of acetaldehyde to which the testes were exposed subsequent to acute ethanol administration to mice; and (2) examining the effect of ethanol on testosterone in animals subsequent to drug pretreatment which decreased or increased ethanol-derived acetaldehyde. Ethanol-induced (3 g/kg) depression of testosterone was dependent upon gonadotropin stimulation. The increase in hCG-induced testosterone was suppressed (P less than 0.01) in ethanol- as compared to saline-treated animals [39.8 +/- 2.6 (S.E.M.) vs 28.1 +/- 2.3 ng/ml]. Pargyline (100 mg/kg) or cyanamide (8.4 mg/kg) increased (P less than 0.05) plasma and testicular acetaldehyde, while having no effect on the testosterone response to ethanol. Similarly, 4-methylpyrazole (25 mg/kg) reduced blood and testicular acetaldehyde to nondetectable levels, while having no effect on testosterone. Testicular acetaldehyde was lower (P less than 0.001) than plasma levels (14 +/- 2 vs 2.0 +/- 0.2 microM). This functional blood-testis barrier to acetaldehyde could be explained by testicular aldehyde dehydrogenases in the mitochondria (Km for acetaldehyde = 1.5 microM) and in the cytosol (Km = 123 microM) whose maximal activities totaled to more than 25-fold greater than that of testicular alcohol dehydrogenase (ADH). ADH was concentrated in the Leydig cells, while aldehyde dehydrogenase was evenly distributed in the testis. Ethanol prevented further hCG-induced rises in testosterone rather than inhibiting testosterone production to below pre-ethanol values. The above data argue against a significant role of acetaldehyde in the in vivo response of testosterone to ethanol. Ethanol appears to impair gonadotropin-testicular receptor interaction in vivo.     

Blood Acetaldehyde Levels in Alcohol-Dosed Rats After Treatment with Anit,Antu, Dithiocarbamate Derivatives,or Cyanamide

ABSTRACT

In adult female Wistar rats, pretreated by gavage with two doses - 16 or 256 μmol/kg - of cyanamide, TMTD (tetramethylthiuram disulfide), TMTM (tetramethylthiuram monosulfide), Ziram or Zineb at 90 min or 18 h before administration of 2 g of ethanol/kg i.p., the blood acetaldehyde levels were significantly increased for 90 - 240 min after ethanol administration (exceptions were noted after exposure to Zineb for 90 min or to low-dosed cyanamide for 18 h). After pretreatment for identical periods with ANTU (N-1-naphthylthiourea) or ANIT (1-naphthylisothiocyanate) at doses extending into the LD₅₀ range, the blood acetaldehyde levels of rats given the same dose of ethanol remained uninfluenced. The increase in blood acetaldehyde recorded after 16 μmol/kg p.o. of TMTM and TMTD remained detectable for up to 48 h. Onset of the cyanamide action occurred already after 45 min. While recognizing that results from animal experiments cannot be transposed without restriction to the human situation, it is concluded that occupational contacts with ANTU or ANIT are not likely to elicit increased blood acetaldehyde levels in man after ingestion of alcohol. The risk of an ethanol intolerance reaction due to a rise in blood acetaldehyde therefore does not appear to be warranted. The present findings indicate, however, that exposure to TMTD, TMTM, Ziram, Zineb or cyanamide is associated with a definite health risk; because of the long persistence of these substances in the body, the risk exists for a long time post-exposure.     

Blood acetaldehyde and the ethanol-induced increase in splanchnic circulation

Acute oral administration of ethanol significantly increases (50-60%) portal blood flow to the liver. As earlier studies have indicated that this effect is maximal at concentrations of ethanol that saturate the alcohol dehydrogenase (ADH) system and is blocked by the ADH inhibitor 4-methylpyrazol, we investigated the possible role of acetaldehyde, a product in the ADH reaction, as a mediator of this effect. In the first series of experiments it was shown that, contrary to expectations, cyanamide administration prior to alcohol suppressed fully the effect of ethanol on portal blood flow without altering it in the absence of ethanol [ethanol = 69.5 +/- 5.6; ethanol + cyanamide 42.9 +/- 2.4; control = 43.0 +/- 3.0; cyanamide = 55.1 +/- 3.7 ml X min-1 X (kg body wt)-1]. Arterial blood concentrations of acetaldehyde were elevated from 3.6 +/- 0.3 microM in the presence of ethanol to 293 +/- 48 microM in the presence of ethanol + cyanamide. Infusion of acetaldehyde either into the left ventricle, resulting in arterial blood acetaldehyde levels of 227 +/- 77 microM, or into the portal circulation, resulting in arterial blood levels of 198 +/- 40 microM, did not modify portal blood flow or splanchnic hemodynamics, nor the effect of ethanol per se. The combination of cyanamide + ethanol significantly reduced total peripheral resistance (from 28 +/- 3 to 19 +/- 2 dyne X cm X sec-5), while neither ethanol or cyanamide per se, nor acetaldehyde affected total peripheral resistance. Data suggest that acetaldehyde is not involved in the ethanol-mediated increase in portal vein flow. Further studies indicate that the effects of cyanamide in suppressing the ethanol-induced increase in portal blood flow and increasing total peripheral resistance appear to be related to an ethanol-cyanamide interaction which is independent of the acetaldehyde levels in the circulation.     

Clinical Responses in Relation to Blood Acetaldehyde Levels

Abstract: A study was undertaken to examine the relationship between blood acetaldehyde levels and clinical responses in volunteers receiving the anti-alcohol drugs disulfiram and calcium cyanamide. In the first part of this study volunteers received different doses of disulfiram (125 mg and 500+250 mg), of calcium cyanamide (25 mg, 50 mg and 100 mg) and of ethanol (0.2 g/kg orally and 0.5 g/kg intravenously). The ensuing interactions ranged from no reaction at all to an intense hypotensive cyanamide-ethanol reaction (CER). A blood acetaldehyde concentration-effect relationship was suggested. In the second part of this study seven subjects received 50 mg of calcium cyanamide 4 hr prior to an intravenous ethanol dose of 0.2 g/kg. The maximum blood level of acetaldehyde ranged from 16 to 241 μM. Aversive interactions started to occur at acetaldehyde levels around 40–60 uM. Changes in flushing reaction and diastolic blood pressure appeared best to reflect changing blood acetaldehyde levels. As a rule, however, the expected cyanamide-ethanol and disulfiram-ethanol reactions are more clearly registered as an increase in acetaldehyde levels than as the ensuing physiological responses.     

Binge ethanol administration enhances the MDMA-induced long-term 5-HT neurotoxicity in rat brain

Rationale Ecstasy abuse commonly occurs in hot, overcrowded environments in combination with alcohol. Around 90% of ecstasy users take ethanol; over 70% of these users also often drink alcohol at hazardous levels.Objectives We wished to examine whether binge ethanol administration enhanced the long-lasting 5-HT neurotoxicity induced by 3,4-methylenedioxymethamphetamine (MDMA) in rats maintained at high ambient temperature and the role of acetaldehyde.Materials and methods Rats were treated with a 4-day ethanol regimen leading to plasma ethanol levels of around 450 mg/dl. On day 5, rats were placed at 30°C and administered MDMA (5 mg/kg). Rectal temperature and hydroxyl radical formation were measured immediately before and up to 6 h after MDMA. 5-HT concentration and 5-HT transporter density were determined 7 days later. A group of rats received cyanamide (50 mg/kg) on days 1 and 3 of the 4-day-ethanol inhalation.Results In ethanol treated rats, MDMA produced a hyperthermic response similar to that observed in controls but enhanced the loss of 5-HT concentration and 5-HT transporter density in the hippocampus. Cyanamide elevated the plasma acetaldehyde concentration fivefold to sevenfold, reduced the MDMA-induced hyperthermia and increased the neuronal damage with neurotoxicity also appearing in the cortex. MDMA increased hydroxyl radical production in the hippocampus, the effect being more marked in rats pre-exposed to ethanol.Conclusions Binge ethanol administration enhances the MDMA-induced long-term 5-HT neurotoxicity by a mechanism not related to changes in acute hyperthermia but probably involving hydroxyl radical formation. The magnitude of this effect is more pronounced after increasing plasma acetaldehyde levels by aldehyde dehydrogenase inhibition.     

Clinical responses in relation to blood acetaldehyde levels.

A study was undertaken to examine the relationship between blood acetaldehyde levels and clinical responses in volunteers receiving the anti-alcohol drugs disulfiram and calcium cyanamide. In the first part of this study volunteers received different doses of disulfiram (125 mg and 500 + 250 mg), of calcium cyanamide (25 mg, 50 mg and 100 mg) and of ethanol (0.2 g/kg orally and 0.5 g/kg intravenously). The ensuing interactions ranged from no reaction at all to an intense hypotensive cyanamide-ethanol reaction (CER). A blood acetaldehyde concentration-effect relationship was suggested. In the second part of this study seven subjects received 50 mg of calcium cyanamide 4 hr prior to an intravenous ethanol dose of 0.2 g/kg. The maximum blood level of acetaldehyde ranged from 16 to 241 microM. Aversive interactions started to occur at acetaldehyde levels around 40-60 microM. Changes in flushing reaction and diastolic blood pressure appeared best to reflect changing blood acetaldehyde levels. As a rule, however, the expected cyanamide-ethanol and disulfiram-ethanol reactions are more clearly registered as an increase in acetaldehyde levels than as the ensuing physiological responses.     

The ethanol metabolite acetaldehyde inhibits the induction of long-term potentiation in the rat dentate gyrus in vivo.

1. Ethanol has been reported to inhibit the induction of long-term potentiation (LTP) in the hippocampus. However, the correlation between the effects of ethanol in vivo and in vitro remained unclear. In addition, previous works have little considered the possibility that the effect of ethanol is mediated by its metabolites. To solve these problems, we investigated the effects of ethanol and acetaldehyde, the first metabolite in the metabolism of ethanol, on the induction of LTP at medial perforant path-granule cell synapses in the dentate gyrus of anaesthetized rats in vivo. 2. Oral administration of 1 g kg-1 ethanol significantly inhibited the induction of LTP, confirming the effectiveness of ethanol in vivo. 3. A lower dose of ethanol (0.5 g kg-1) failed to inhibit the induction of LTP in intact rats, but significantly inhibited LTP in rats treated with disulfiram, an inhibitor of aldehyde dehydrogenase, demonstrating that LTP is inhibited by acetaldehyde accumulation following ethanol administration. 4. Intravenous injection of acetaldehyde (0.06 g kg-1) significantly inhibited the induction of LTP. 5. The inhibitory effect of acetaldehyde on LTP induction was also observed when it was injected into the cerebroventricules, suggesting that acetaldehyde has a direct effect on the brain. The intracerebroventricular dose of acetaldehyde effective in inhibiting LTP induction (0.1 - 0.15 mg brain-1) was approximately 10 fold lower than that of ethanol (1.0 - 1.5 mg brain-1). 6. It is possible that acetaldehyde is partly responsible for memory impairments induced by ethanol intoxication.