Effects of gamma-butyrolactone,amphetamine, and haloperidol in mice differing in sensitivity to alcohol

Gamma-butyrolactone (GBL) induced longer loss of righting reflex in mice (LS-line) selectively bred for greater sensitivity to ethanol than in less sensitive SS-line mice. GBL also induced a three-fold greater increase of brain dopamine levels in LS than in SS mice. Among three inbred strains, GBL-induced loss of righting reflex was greater in BALB/c, and greater in DBA/2 than in C57BL/6 mice. A low dose of GBL produced biphasic effects on locomotor activity. Both an initial depressant action and a later increase in activity were greater in LS than in SS mice. These GBL effects on activity were modified in a genotypedependent fashion by amphetamine. Results of these experiments as well as greater catalepsy-inducing properties of haloperidol in SS mice suggest that genotypic influences on motor reactivity to ethanol may be modeled by GBL effects on brain dopamine systems.     

An evaluation of the locomotor stimulating action of ethanol in rats and mice

The locomotor activity of groups of three CD-1 female mice was increased by 1.0 and 2.0 g/kg ethanol, IP, was decreased during the first hour and increased during the second hour by 3.0 and 4.0 g/kg, and was decreased by 5.0 g/kg. The dose (2.0 g/kg) that caused the greatest increase in locomotor activity did not impair motor coordination, measured by the height of aerial righting in mice. Tests after oral administration of ethanol showed that the increase in locomotor activity of mice was not due to peritoneal irritation. The same dose (2.0 g/kg) did not increase the locomotor activity of C57BL/6J mice. Ethanol (0.1 to 3.0 g/kg) had no effect or decreased the locomotor activity of individual male Sprague-Dawley rats. These findings suggest that biological differences in strains and species of laboratory rodents contribute to the apparent variability of locomotor stimulation caused by ethanol. The presence or absence of an ethanol-induced increase in locomotor activity was not dependent on the sex or number of mice or rats tested. Intertrial-interval crossing by rats acquiring or performing an active avoidance task in a shuttle box was increased by ethanol. This action was dependent on the presentation of electric foot shock. Apomorphine (0.25 and 2.5 mg/kg) and fenmetozole (7.5 and 15.0 mg/kg) failed to inhibit the ethanolinduced increase in intertrial-interval crossing by rats, although these drugs have been shown previously to antagonize the ethanol-induced increase in the activity of mice ethanol treatment. The ethanol-induced increases in the spontaneous locomotor activity of CD-1 mice in photocell activity monitors and in intertrial-interval crosses in rats in a shuttle box task thus do not appear to share a common mechanism.     

Behavioral characterization of acetaldehyde in C57BL/6J mice: locomotor, hypnotic, anxiolytic and amnesic effects

Rationale Acetaldehyde, the first metabolite of ethanol, was recently suggested to contribute to many behavioral effects of ethanol, although few studies have directly investigated the behavioral effects of acetaldehyde itself.Objectives The aim of the present study was to characterize the locomotor, hypnotic, anxiolytic-like and amnesic effects of acetaldehyde in C57BL/6J mice.Methods Increasing doses of acetaldehyde (0–300 mg/kg) were injected intraperitoneally and their effects on a series of representative behaviors were investigated. The locomotor effects of acetaldehyde were measured in activity boxes. The duration of the loss of righting reflex was used as an index of the hypnotic effects of acetaldehyde. The anxiolytic-like effects of acetaldehyde were tested with an elevated plus-maze and the amnesic effects with the one-trial passive avoidance test. Finally, brain and blood acetaldehyde concentrations were assessed.Results Acetaldehyde induced a significant hypolocomotor effect at 170 mg/kg and higher doses. In addition, the hypnotic effects of acetaldehyde were demonstrated by a loss of righting reflex after the administration of 170 and 300 mg/kg acetaldehyde. The elevated plus-maze showed that acetaldehyde does not possess anxiolytic-like properties. Finally, acetaldehyde (100–300 mg/kg) dose-dependently altered memory consolidation as shown by a reduced performance in the passive avoidance test.Conclusions The present results show that acetaldehyde induces sedative, hypnotic and amnesic effects, whereas it is devoid of stimulant and anxiolytic-like properties in C57BL/6J mice. However, the behavioral effects of acetaldehyde after intraperitoneal administration were apparent at very high brain concentrations. The present results also indicate that acetaldehyde is unlikely to be involved in the anxiolytic properties of ethanol in mice.     

Cocaine produces low dose locomotor depressant effects in mice

Cocaine produces several behavioral effects, most notably locomotor stimulation. Biochemically, cocaine is known to inhibit reuptake at the three monoamine transporter sites, and may have highest affinity at the serotonin transporter. Serotonin augmentation has been associated with decreases in behavioral activity, but cocaine has not been reported to produce behavioral depressant effects except at high doses which cause stereotypy and disruption of behavior. This study examined the effects of relatively low doses of cocaine, in the range of 0.1–10 mg/kg, on locomotor activity in C57BL/6J and DBA/2J mice. A biphasic dose-response curve was seen for both strains. At the lowest doses, activity was depressed. As the dose of cocaine increased, activity returned to baseline, and at the highest doses, increases in locomotor activity were found. DBA/2J mice were depressed at a lower dose of cocaine than were C57BL/6J mice; however, C57BL/6J mice showed locomotor depression over a broader range of doses. Activity was maximally depressed at 0.1 mg/kg for DBA/2J mice, and maximally depressed at 0.3 mg/kg for C57BL/6J mice. Thus, low doses of cocaine are shown to produce significant decreases in locomotor activity in two strains of mice. It is postulated that these low doses of cocaine which depress locomotor activity do so via inhibition of serotonin uptake, resulting in potentiation of serotonergic activity.     

An analysis of cocaine effects on locomotor activities and heart rate in four inbred mouse strains

The effects of cocaine on Y-maze activity and heart rate have been examined in four inbred strains of mouse (BALB, C57BL, C3H and DBA). In addition, brain [3H]-cocaine concentrations were measured at the time of maximal response to cocaine. Cocaine produced a dose-related increase in Y-maze cross activity in C3H, DBA and C57BL, with C3H mice being considerably more sensitive than DBA or C57BL. Cocaine was without effect on Y-maze cross activity in BALB mice. Cocaine produced a biphasic effect on rearing activity in C3H mice, a dose related depression in BALB mice, and was without effect on C57BL and DBA mice. At the highest dose studied (15 mg/kg), cocaine produced a small decrease in heart rate in C3H mice. Strain differences in behavior were maximal 15 minutes after a dose of 5 mg/kg, IP. At this dose and time interval, brain [3H]-cocaine concentrations were not significantly different among the four strains of mice. The results suggest a genetically-determined difference in CNS sensitivity to cocaine.     

Behavioral interactions of ethanol and methylxanthines

The effect of the methylxanthines caffeine, theophylline and isobutylmethylxanthine (IBMX) on ethanol-induced ataxia and loss of righting reflex was investigated in three strains of mice. A significant potentiation of ethanol-induced ataxia was produced in all strains of mice at 20, 45 and 75 min after ethanol in mice pretreated with 62.5 mg/kg caffeine and 12.5 mg/kg IBMX. In mice pretreated with 40 mg/kg caffeine potentiation of ethanol-induced ataxia was observed only at 20 min after ethanol. Theophylline pretreatment produced no alteration in ethanol-induced ataxia. The results of methylxanthine pretreatment on ethanol-induced ataxia were similar, regardless of a shorter (10 min) or longer (75 min) pretreatment time. The methylxanthines produced no effect on motor coordination or behavior when administered separately. Although ethanol-induced loss of righting reflex was shortened by theophylline, neither caffeine nor IBMX altered the duration of loss of righting reflex. It is possible that inhibition of adenosine uptake, a known effect of the methylxanthines, may be a more likely explanation for the modulation of the behavioral effects of ethanol.     

Inherent differences in sensitivity to methylxanthines among inbred mice

The behavioral effects of caffeine, theophylline, paraxanthine, and theobromine on locomotor activity were analyzed in four strains of inbred mice that were previously shown to differ in their acute toxic responses to caffeine administered at high dosages. Dose response curves for the effects of caffeine, theophylline, paraxanthine and theobromine on locomotor activity were established in CBA/J, C57BL/6J, DBA/2J and SWR/J strains of inbred mice. Paraxanthine was the maximally effective methylxanthine in the CBA/J, DBA/2J and SWR/J strains, while in the C57BL/6J strain, caffeine was the maximally effective methylxanthine. Theophylline failed to stimulate locomotor activity in the C57BL/6J strain and theobromine failed to stimulate activity in all of the strains tested. Decreases in locomotor activity were seen at the 100 mg/kg dose of caffeine in the C57BL/6J mice and at the 100 mg/kg dose of theophylline in the C57BL/6J, DBA/2J and SWR/J strains. Theobromine produced decreases in locomotor activity in the C57BL/6J, DBA/2J and SWR/J strains of mice. In contrast to the other methylxanthines, paraxanthine failed to decrease activity across the range of doses tested (1.0-150 mg/kg). These data suggest that the methylxanthines have genetically specified multiple modes of action upon locomotor activity and that the use of genetically distinct strains of mice may have important value in the neurochemical and pharmacological dissection of methylxanthine-induced behavioral effects.     

Effects of naloxone and naltrexone on locomotor activity in C57BL/6 and DBA/2 mice

Administration of naloxone or naltrexone in DBA/2 (DBA) mice was followed by dose related depressant effects. The locomotor activity of the C57BL/6 (C57) mice injected with naltrexone was also depressed. Low doses of naloxone induced a decrease in activity in the C57 strain. This effect gradually disappeared at intermediate doses and recurred again at higher doses. The results are discussed in terms of differences in type number and/or distribution of the receptors influenced by naloxone and naltrexone in the two strains of mice tested.     

Ethanol-induced mouse strain differences in locomotor activity.

C57BL/6J mice showed dose dependent devreases in locomotor activity with increasing IP doses of ethanol (0.0, 0.75, 1.50 and 2.25 g/kg), while BALB/cJ mice showed dose dependent increases in activity; both strains were equally active with saline. Whether this finding represents decreased CNS responsivity in C57BL mice to ethanol's excitatory effect or increased response to its depressant action at sub-hypnotic doses is unclear, since anesthetic doses produce anesthesia of far shorter duration in the C57BL strain than in the BALB strain. It is possible that the biphasic action of alcohol is under the control of separate and distinct mechanisms, rather than a common one, and that these two mechanisms are differentially affected by alcohol. Endogenous as well as ethanol-induced neurochemical differences in biogenic amines may also be correlated with the gentic variation in CNS responsivity towards alcohol.     

Taurine and ethanol interactions: behavioral effects in mice

Taurine is an abundant amino acid in the brain that shares pharmacological effects and similar potency with ethanol. Recently, taurine-containing beverages have been reported to enhance the euphoric effects of ethanol, though the extent of this effect and the role of taurine remain speculative. The present study was designed to explore interactions between taurine and ethanol on several behaviors including locomotion, ataxia, and loss of righting. Two strains of mice, C57BL/6J and DBA/2J mice, were used to examine potential strain differences. In the first experiment, effects of various doses of taurine (0.3-3.0 g/kg), ethanol (1.0-4.2 g/kg), or taurine in combination with ethanol were assessed in a within-subjects design. Although taurine did not appear to alter effects of ethanol on any measure in either strain, the development of tolerance to locomotor effects and sensitization to ataxic effects of ethanol in DBA/2J mice complicated interpretation of these results. In a second experiment, drug-na?ve mice were assigned to one of four treatment groups: saline+saline, saline+ethanol (1.78 g/kg), taurine (1.78 g/kg)+saline, or ethanol+taurine. In this experiment, taurine pretreatment significantly attenuated the locomotor-stimulating effect of ethanol in both strains (but to a greater extent in C57BL/6J mice) and appeared to reduce the ataxic effects of ethanol in C57BL/6J mice. In conclusion, the interaction between taurine and ethanol is subtle. Further, results are inconsistent with the notion that taurine plays a major role in the locomotor, ataxic, or loss of righting effects of ethanol.     

Strain dependent effects of ketamine on locomotor activity and antinociception in mice

The effects of ketamine (12.5, 25 and 50 mg/kg) on locomotor activity and response to nociceptive stimuli were investigated in the inbred strains of mice: BALB/c (BALB), C57BL/6 (C57) and DBA/2 (DBA). In the BALB and in the C57 mice ketamine exerted activity stimulating effects, which were already present at doses lower than those inducing antinociception. Locomotor depressant effects were evident in the DBA mice following the administration of doses higher than those necessary to induce analgesia. It is suggested that: (1) ketamine affects locomotor activity and response to painful stimuli through different mechanisms, (2) the brain regional and biochemical differences reported for the strains considered may account for their different responses to ketamine administration.     

Age and strain differences in the rate of development of functional tolerance to ethanol by mice

The time course of development of functional tolerance to ethanol was investigated in mice during the inhalation of ethanol vapour, using loss of righting reflex as the behavioural end-point. In male mice of the TO Swiss strain, weanling mice (18 days) showed no development of tolerance during continuous or repeated exposure to ethanol vapour for 6 h. Adolescent TO Swiss mice (35–40 days) showed rapid development of functional tolerance, reaching a state where 2x the original effective concentration of ethanol in blood was required to produce loss of righting reflex within 5 h. Older adult mice (150–200 days) showed some development of tolerance during continuous or repeated exposure to ethanol for 5 h but this was much less than that seen in adolescent mice. When adolescent males of the C57BL, TO Swiss and DBA2 strains were compared, marked differences were observed. C57BL mice showed very rapid development of functional tolerance to ethanol in which more than 2 × the original effective dose was required to produce loss of righting reflex after about 3 h of ethanol exposure. TO Swiss mice showed somewhat slower development of ethanol tolerance. DBA2 mice showed little evidence of development of functional tolerance over the time course of these experiments. Evidence was also obtained that similar age and strain differences may exist with respect to tolerance to the hypothermic effects of ethanol. These results are discussed in relation to current concepts of ethanol sensitivity, tolerance and physical dependence.     

Effect of tolbutamide and chlorpropamide on acetaldehyde metabolism in two inbred strains of mice

The mechanisms by which chlorpropamide and tolbutamide disrupt acetaldehyde metabolism were studied in C57BL and DBA mice. Acute po administration of varying doses of tolbutamide or chlorpropamide 2.5 hr before a 3.0 g/kg ip dose of ethanol to C57BL and DBA mice resulted in significant elevations of blood acetaldehyde when measured 2.5 hr after ethanol dosing. Dose-response analysis revealed a significant (p less than .05) difference in ED50 values for the elevated blood acetaldehyde response to tolbutamide in DBA (60 mg/kg) and C57BL (100 mg/kg) mice. The ED50 value for potentiation by chlorpropamide of blood acetaldehyde concentration was similar (23 to 32 mg/kg) in both inbred strains. At higher doses of chlorpropamide, DBA mice displayed elevations of blood acetaldehyde nearly threefold greater than those measured in C57BL mice treated identically. Measurements of aldehyde dehydrogenase (ALDH) in hepatic subcellular fractions, obtained from both inbred strains treated with 100 mg/kg tolbutamide or chlorpropamide prior to a 3.0 g/kg dose of ethanol, revealed a 50 to 80% inhibition of the low-Km ALDH present in mitochondria. Chlorpropamide and tolbutamide did not inhibit ALDH in vitro, suggesting that metabolites of these hypoglycemic agents may be responsible for the genotypic-dependent alterations in in vivo acetaldehyde oxidation.     

Rapid ethanol tolerance mediated by adaptations in acute tolerance in inbred mouse strains

It has been postulated that decreased acute sensitivity to ethanol is an important genetically-mediated risk factor for the development of alcoholism. Previous work in mice and rats has indicated that ethanol sensitivity can be reduced in a genotype-dependent manner by a single dose of ethanol 24 h prior to testing, so-called 'rapid' tolerance. The current studies were undertaken to determine if the observed rapid tolerance was mediated by alterations in initial sensitivity or acute functional tolerance (AFT), the two primary components of acute sensitivity. Separate groups of C57BL/6, DBA/2, ILS, and ISS inbred mouse strains were administered a single pretreatment dose of saline or ethanol (5 g/kg). The original and modified versions of the loss of righting reflex test, ethanol-induced hypothermia, and ataxia on a stationary dowel rod were tested 24 h later. Dependent on the test and strain, varying degrees of rapid tolerance were observed; a pronounced sensitization was detected in one case. There was a concomitant increase in the rate and/or magnitude of AFT with little change in initial sensitivity suggesting that rapid tolerance was mediated primarily by alterations in AFT. This conclusion may have implications for the contribution of acute sensitivity to human alcoholism.     

Acute tolerance in inbred and selected lines of mice

Mice of the C57Bl and C3H strains regained their righting reflex at higher brain ethanol levels than those at which they had lost their righting reflex, indicating that these animals developed acute tolerance. DBA mice did not develop acute tolerance. DBA mice "slept" significantly longer than C57Bl mice, but all mice lost their righting reflex at similar brain ethanol levels. Mice of SS and LS lines also showed no evidence for developing acute tolerance but differed significantly in brain ethanol levels upon loss of righting reflex. Both acute tolerance development and initial brain sensitivity to ethanol seem to determine duration of ethanol "sleep time" in mice.     

Interactions of antidepressants and ethanol on spontaneous locomotor activity and rotarod performance in NMRI and C57BL/6 mice

In order to find appropriate doses for studying antidepressant-ethanol interaction in two mouse strains, spontaneous locomotor activity and rotarod performance were first studied in NMRI mice after amitriptyline 3-30 mg/kg, mianserin 3-30 mg/kg, nomifensine 1- 10 mg/kg, citalopram 3-100 mg/kg, and ethanol 1-3 g/kg intraperitoneally. Ethanol increased significantly locomotor activity at 1 g/kg and impaired rotarod performance at 2 and 3 g/kg. Amitriptyline and mianserin decreased dose-dependently locomotor activity at doses ≥ 10 mg/kg. Nomifensine and citalopram increased locomotor activity at 10 mg/kg and citalopram 100 mg/kg decreased it. Rotarod performance was affected only by amitriptyline 10 and 30 mg/kg and citalopram 100 mg/kg, which impaired performance. Interaction studies with the two strains using amitriptyline, mianserin, nomifensine and citalopram 10 mg/kg and ethanol 1 g/kg showed that C57BL/6 mice were less sensitive than NMRI mice to the stimu lating effects of ethanol and more sensitive to impairment of rotarod performance by amitrip tyline and mianserin. C57BL/6 mice had a significantly poorer baseline performance on rotarod, and the citalopram plus ethanol combination impaired their performance severely, although drugs alone did not impair this test. The results suggest that decreased locomotor activity as a measure of antidepressant-induced sedation does not parallel with impaired performance on rotarod and that significant strain differences can be seen in psy chopharmacological tests and responses to drugs in mice.     

Comparative metabolism of benzene and trans,trans-muconaldehyde to trans,trans-muconic acid in DBA/2N and C57BL/6 mice

Our laboratory recently identified trans,trans-muconaldehyde (MUC), a six-carbon diene dialdehyde, as a hematotoxic microsomal metabolite of benzene (Latriano et al., Proc Natl Acad Sci USA 83: 8356-8360, 1986). We also showed that MUC is metabolized in vitro to trans,trans-muconic acid (MA), a six-carbon diene dicarboxylic acid and known urinary metabolite of benzene. To elucidate further the role of ring-opened metabolites in benzene toxicity, the metabolism of benzene and MUC was examined in the benzene sensitive DBA/2N mouse strain and the less benzene sensitive C57BL/6 strain. A sensitive assay for urinary MA analysis was developed. The percent of benzene dose excreted as urinary MA within the first 24 hr after treatment decreased with an increase in benzene dose, i.e. from 9.8 to 0.4% in DBA/2N mice and from 17.6 to 0.2% in C57BL/6 mice treated with 0.5 to 880 mg/kg benzene. DBA/2N mice excreted significantly (P less than or equal to 0.05) more MA compared with C57BL/6 mice after treatment with hematotoxic benzene doses (220-880 mg/kg). At low benzene doses (0.5 to 2.5 mg/kg), C57BL/6 mice excreted significantly (P less than or equal to 0.05) more MA compared with DBA/2N mice. There were no significant differences in the metabolism of MUC to MA between the two strains after treatment with 0.5 to 3.0 mg/kg. Furthermore, mice from both strains excreted similar amounts of muconic acid when treated with 0.7 to 7.1 mg/kg MA. These results are consistent with the hypothesis that reactive ring-opened metabolites such as trans,trans-muconaldehyde play a role in benzene hematotoxicity. Sensitivity towards benzene may be due, in part, to increased metabolism to ring-opened compounds.     

Different effects of apomorphine on climbing behavior and locomotor activity in three strains of mice

Apomorphine (0.1, 0.25, 0.5, 1, 3 mg/kg, SC), induces a dose-dependent reduction of locomotor activity in DBA/2(DBA) and BALB/c(BALB) mice, while it enhances locomotor activity in a biphasic way in C57BL/6(C57) mice. On the other hand, apomorphine is ineffective in modifying climbing behavior in DBA mice while it increases climbing behavior in C57 and BALB mice. The results, taken together, suggest that these are two different behaviors, possibly controlled by different dopaminergic mechanisms depending on the genetic makeup.     

Studies on the interaction between ethanol and amfonelic acid

Amfonelic acid (AFA), a non-amphetamine central stimulant dose-dependently reduced the hypnotic effect of ethanol in C57B1/6 mice. It did not enhance the elimination of ethanol. Amfonelic acid failed to modify the duration of pentobarbitone-induced hypnosis or the ethanol-induced hypothermia in these animals. Combined treatment with amfonelic acid and a lipophilic alpha 1-adrenoceptor agonist was not more effective than amfonelic acid alone in blocking ethanol hypnosis. The stimulation of locomotor activity by amfonelic acid in C57B1/6 mice was more sensitive to the blocking effect of ethanol than stimulation induced by d-amphetamine. The blocking effect of amfonelic acid, but not that of d-amphetamine, on the effects of ethanol developed tolerance. In pimozide-pretreated mice, amfonelic acid failed to reduce the ethanol-induced hypnosis. Hence it appears that dopamine (DA) released by amfonelic acid is responsible for its antagonism of ethanol. However, though amfonelic acid acted as a strong releaser of DA in Swiss-Webster, CD-1, DBA-2 and BALB/c mice, in these strains it failed to reduce the effect of ethanol. Moreover, methylphenidate, a dopaminergic stimulant, which acts by a mechanism similar to that of amfonelic acid was not effective in reducing the hypnotic effect of ethanol in C57B1/6 mice. For these reasons, additional mechanisms may have to be considered to explain this strain-dependent effect of amfonelic acid.     

A diallel analysis of nicotine-induced hypothermia

The hypothermic responses of mice that occur after acute injection of nicotine show genetic influences. The body temperatures of mice of all five strains tested decreased after injection of either 0.75 or 1.5 mg/kg nicotine, but mice of the C3H strain were less affected than were those of the DBA, BALB, or C57BL strains. Mice of the A strain were the most sensitive to nicotine's effects. Genetic effects on nicotine-induced hypothermia were further examined using a five-by-five diallel cross. Additive genetic variance occurred at both nicotine doses. Substantial dominance variance, including directional dominance toward a large hypothermic response induced by injection of a low dose of nicotine (0.75 mg/kg), suggested that an intense response to a low drug dose is adaptive. The directional dominance was absent after treatment with a high dose (1.5 mg/kg) of the drug. Epistatic interactions occurring in crosses involving C57BL mice were pronounced.