Body temperature influences ethanol and ethanol/pentobarbital lethality in mice

The effect of body temperature on ethanol (ETOH) or ethanol plus pentobarbital (ETOH/PB) lethality was investigated in C57BL/6J mice. Decreasing ambient temperatures from 35-20 degrees C, decreased rectal temperatures from 38-20 degrees C and increased 8-hour survival from 0-93% for ETOH-treated and from 0-100% for ETOH/PB-treated mice. ETOH and ETOH/PB animals with no hypothermia (body temperatures = 38 degrees C) had the highest lethality. Those with body temperatures between 30-32 degrees C had the highest 24-hour survival. These results suggest that controlled hypothermia may be useful in reducing lethality from ethanol or ethanol/combination overdoses.

Body temperature and ethanol pharmacokinetics in temperature-challenged mice

The relationships between ambient temperature, body temperature, ethanol pharmacokinetics and behavioral sensitivity to ethanol were examined in C57BL/6 mice. Mice were injected intraperitoneally with 3.6 or 2.0 g/kg ethanol. Exposure to increasing ambient temperatures of 4-34 degrees C immediately after ethanol injection resulted in a significant increase in body temperature, ethanol elimination rate and brain:blood ethanol concentration ratios in 3.6 g/kg ethanol-injected mice, but not in mice injected with 2.0 g/kg ethanol. As the mean body temperature increased from 26.0 to 38.2 degrees C in the 3.6 g/kg mice, there was a 50% increase in ethanol elimination rate. Delayed (30 min) exposure to increasing ambient temperatures following injection of 3.6 g/kg ethanol resulted in a significant increase in ethanol elimination rate, a marked increase in the duration of loss of righting reflex and a decrease in ethanol concentration at the regain of righting reflex. The results indicate that temperature-induced changes in the absorption, distribution and elimination of ethanol do not appear to mediate the effects of temperature on behavioral sensitivity to ethanol in C57 mice.

Body temperature differentially affects ethanol sensitivity in both inbred strains and selected lines of mice

Offsetting ethanol-induced hypothermia in five inbred strains of mice changed ethanol sensitivity within strains and markedly reduced differences between strains in brain sensitivity to hypnotic ethanol doses. The present study extended this work to mice selectively bred for sensitivity and resistance to ethanol-induced loss of righting reflex (LORR) and hypothermia. In all experiments LORR duration and ethanol concentrations at return of righting reflex were measured after i.p. hypnotic ethanol doses and exposure to 22 or 34 degrees C. In experiment 1, C57BL/6J, A/HeJ, 129/J, LS/lbg and SS/lbg mice were given 4.2 g/kg ethanol. In experiment 2, the same mouse genotypes were tested with different ethanol doses (2.5-4.9 g/kg) selected to produce an equivalent degree of impairment (60 min LORR duration). In experiment 3, HOT and COLD lines of mice were given 4.0 g/kg ethanol. In agreement with previous work, offsetting hypothermia reduced differences between genotypes in ethanol sensitivity. Comparisons within genotypes indicated that ethanol sensitivity in C57, A/He, SS, HOT and COLD mice increased as body temperature increased. In contrast, ethanol sensitivity in 129 and LS mice decreased as body temperature increased. These results extend previous findings indicating that body temperature during intoxication contributes to differences between genotypes in ethanol sensitivity. The present findings also suggest that there are qualitative differences in the effects of temperature on ethanol sensitivity within genotypes.

Interactions between benzodiazepine antagonists, inverse agonists, and acute behavioral effects of ethanol in mice

The behavioral manifestations of acute ethanol intoxication resemble those of benzodiazepines, barbiturates and general anesthetics. This has led to speculation that these drugs share common mechanisms or sites of actions within the brain. The discovery of a specific benzodiazepine receptor site, and the subsequent development of selective receptor antagonist and inverse agonist drugs, provides a framework to test the involvement of the benzodiazepine receptor complex in mediating ethanol's behavioral effects. The partial inverse agonist Ro15-4513, an analog of the benzodiazepine receptor antagonist Ro15-1788 (flumazenil), has been reported to block or reduce some of ethanol's acute effects in rodents by a benzodiazepine receptor-mediated action. There has been some controversy over whether the "antialcohol" effect of Ro15-4513 is a unique property of this compound or is shared by other benzodiazepine antagonists with inverse agonist activity. We have studied the effects of Ro15-4513 and other benzodiazepine receptor antagonists on acute ethanol intoxication in mice and have obtained evidence that 1) Ro15-4513 differentially affects acute effects of ethanol, 2) an "antialcohol" property is not a general feature of all benzodiazepine antagonists and inverse agonists, and 3) "antialcohol" activity may not be unique to Ro15-4513.

Temperature affects ethanol lethality in C57BL/6, 129, LS and SS mice

The effect of ambient and body temperature on ethanol lethality in inbred strains and selected lines of mice was investigated. C57BL/6J, 129/J, LS/Ibg and SS/Ibg mice were exposed to 23 or 34 degrees C following IP injection of lethal ethanol doses (8.2, 6.0, 6.5 or 7.0 g/kg ethanol, respectively). All mice exposed to 23 degrees C during intoxication became markedly hypothermic, with mean body temperatures dropping to lows of 27.9, 30.3, 33.0 and 33.3 degrees C in C57, LS, SS and 129 animals, respectively. Compared to the 23 degrees C groups, exposure to 34 degrees C offset the ethanol-induced hypothermia and significantly increased percent mortality in all four mouse genotypes. Exposure to 34 degrees C increased mortality at 24 hours postinjection from 15% to 95% in SS mice, from 37.5% to 100% in 129 mice and from 50% to 100% in LS and C57 mice. Blood ethanol data suggest that the present results cannot be explained by temperature-related changes in ethanol elimination. These results provide further evidence that body temperature during intoxication can have major effects on mortality rates in mice.

Chronic ethanol exposure increases peripheral-type benzodiazepine receptors in brain

The effect of chronic ethanol exposure, withdrawal from chronic exposure and short-term ethanol exposure on mouse brain peripheral-type benzodiazepine receptors (PBR) and on PBR from selected peripheral tissues was studied. Male C57BL/6J mice were fed an ethanol-containing liquid diet for 7.75 or 9 days under conditions which produced physical dependence. Control mice received the diet with isocaloric carbohydrates substituted for ethanol. The binding of [3H]Ro5-4864 to PBR was increased in brain membranes, but not heart or kidney membranes, of mice exposed to ethanol for 7.75 days. Scatchard plot analysis indicated that the increase was due to an increase in the apparent number of binding sites and not to a change in receptor affinity. The same results were obtained in ethanol-dependent mice that were withdrawn from the ethanol for 12 h prior to binding determinations. The binding of [3H]PK-11195 to brain PBR was likewise increased in mice made physically dependent on ethanol after 9 days exposure. In contrast to the effects of chronic exposure using the liquid diet, repeated short-term exposure to ethanol following a procedure known to cause functional tolerance (3.6 g/kg i.p. once daily for 4 days) did not significantly affect the binding of [3H]Ro5-4864 to brain when compared to saline-injected and naive control mice. The results are consistent with previous findings and suggest that ethanol exposure causes time-dependent changes in brain PBR that may be linked to the development of physical dependence. However, further studies are necessary to determine whether the increase in brain PBR sites of alcohol-dependent mice is causally related to the development of alcohol dependence.

Genetically determined differences in ethanol sensitivity influenced by body temperature during intoxication

The present study investigated the importance of body temperature during intoxication in mediating differences between five inbred strains of mice (C57BL/6J; BALB/cJ; DBA/2J; A/HeJ; 129/J) in their acute sensitivity to the hypnotic effects of ethanol. Mice exposed to 22 degrees C after ethanol injection became hypothermic and exhibited statistically significant differences between strains in rectal temperatures at the return of the righting reflex (RORR), duration of loss of the righting reflex (LORR), and blood and brain ethanol concentrations at RORR. Exposure to 34 degrees C after injection offset ethanol-hypothermia and markedly reduced strain-related differences in rectal temperatures and blood and brain ethanol concentrations at RORR. Brain ethanol concentrations at RORR were significantly lower in C57, BALB, DBA and A/He mice exposed to 34 degrees C compared to mice exposed to 22 degrees C during intoxication suggesting that offsetting hypothermia increased ethanol sensitivity in these strains. Taken with previous in vitro studies, these results suggest that genetically determined differences in acute sensitivity to the behavioral effects of ethanol reflect differences in body temperature during intoxication as well as differences in sensitivity to the initial actions of ethanol at the cellular level.

Antagonism of ethanol-induced depression of mouse locomotor activity by hyperbaric exposure

Previous studies have shown that exposure to hyperbaric helium + oxygen (HEOX) antagonizes the acute depressant effect of hypnotic doses of ethanol on rodent behavior, precipitates and exacerbates withdrawal in ethanol-dependent mice, and attenuates the development of chronic functional ethanol tolerance. The present study extends these investigations to the sub-hypnotic dose range by determining the effect of hyperbaric exposure on ethanol-induced depression of locomotor activity. Male C57BL/6J mice were given two treatments, 2.5 g/kg ethanol and saline, spaced one week apart according to a within subjects, balanced crossover design. Following injection, animals were exposed individually to 1 atmosphere absolute (ATA) air or to 1 ATA or 12 ATA HEOX inside a 15 liter hyperbaric chamber. Chamber temperatures were adjusted to offset ethanol hypothermia and the cooling effect of helium. Locomotor activity was measured continuously, beginning 10 min after injection, and recorded at prescribed intervals for 60 min. Multivariate analysis of variance of the measured activity revealed statistically significant differences between groups based on atmospheric condition, treatment, and time after injection. Within group comparisons indicated that ethanol treatment induced a significant reduction in locomotor activity in mice exposed to either 1 ATA air or 1 ATA HEOX. In contrast, ethanol-injected mice exposed to 12 ATA HEOX did not show a significant ethanol-induced decrease in locomotor activity, indicating antagonism of ethanol's effect. Hyperbaric exposure did not significantly alter blood ethanol concentrations measured 70 min after ethanol injection, thus making a pharmacokinetic explanation for these results unlikely. These findings are consistent with, and extend, previous evidence suggesting that hyperbaric exposure antagonizes molecular actions of ethanol leading to intoxication.

Ro15-4513 differentially affects ethanol-induced hypnosis and hypothermia

Recent reports of in vivo antagonism of the acute anti-conflict, ataxic, and lethal effects of ethanol with the partial inverse agonist imidazobenzodiazepine Ro15-4513 implicate the GABAa/benzodiazepine receptor in mediating several acute effects of ethanol. These data raise the question as to whether all of the acute effects of ethanol can be antagonized by Ro15-4513. The present study addressed this issue by investigating the effect of Ro15-4513 on ethanol-induced loss of righting reflex and hypothermia in mice. We found that Ro15-4513 antagonized the hypnotic, but not the hypothermic, effects of ethanol when tested under identical conditions. These results suggest that the GABAa/benzodiazepine receptor may not be involved in mediating all pharmacological effects of ethanol.

Chronic functional ethanol tolerance in mice influenced by body temperature during acquisition

Previous studies have found that body temperature during intoxication influences brain sensitivity to ethanol with the sensitivity being less at cool than at warm body temperatures. If this effect of temperature reflects alterations in the acute membrane perturbing action of ethanol, as suggested by in vitro studies, then body temperature reduction (hypothermia) during tolerance acquisition should reduce the effectiveness of a given ethanol concentration and, in turn, should reduce the development of chronic functional ethanol tolerance. To test this hypothesis, adult drug-naive C57BL/6J mice were injected i.p. once daily for five days with 3.6 g/kg ethanol (20% w/v) and were exposed to 34 degrees C or 25 degrees C for five hours following injection. On day 6, both ethanol acquisition groups and naive mice were injected i.p. with 4.0 g/kg ethanol and exposed to 25 degrees C. During acquisition, the group exposed to 34 degrees C had significantly higher body temperatures than the mice exposed to 25 degrees C, and there were no statistically significant differences in blood ethanol concentrations between treatment conditions. The extent of tolerance on day 6, measured by sleep-times and wake-up blood and brain ethanol concentrations versus naive mice, was significantly greater in the 34 degrees C acquisition group than in the 25 degrees C acquisition group. The results demonstrate that body temperature influences tolerance development in the manner predicted by membrane perturbation theories of anesthesia and adaptation based tolerance theories.

Rectal and brain temperatures in ethanol intoxicated mice

The present study tested the assumption that deep rectal temperature reflects brain temperature in ethanol-intoxicated mice exposed to a range of ambient temperatures. Adult C57BL/6J mice were injected IP with one of three hypnotic doses of ethanol (3.2, 3.6, or 4.0 g/kg, 20% w/v) or with normal saline and were exposed to ambient temperatures of 15, 22, 32, or 34 degrees C. Thirty minutes post-injection, the mice were killed by cervical dislocation, decapitated and their rectal and brain temperatures were recorded simultaneously. Rectal and brain temperatures in the intoxicated mice increased significantly as the ambient temperature increased and were highly correlated and linearly related with each other. Although correlated, brain and rectal temperatures in these mice did not change in parallel, with brain temperatures increasing less rapidly than rectal temperatures. Additional studies indicated that similar relationships (correlated, but non-parallel) exist between the brain and rectal temperatures at 60, 120, and 180 min after injection of 3.6 g/kg ethanol. These findings suggest that rectal temperature can be used to quantify brain temperature in intoxicated mice, and extend to intoxicated animals evidence that brain temperature is controlled independently from rectal temperature.

Ethanol-induced inhibition of mouse brain adenosine triphosphatase activities: lack of interaction with norepinephrine in vitro

The in vitro effects of ethanol on C57BL/6J mouse forebrain ATPase activities were investigated in the presence and absence of norepinephrine. Three enzyme activities (Na + K-ATPase, Mg-ATPase, and low affinity Ca-ATPase) were studied in forebrain homogenates using a colorimetric assay. The effect of norepinephrine on ethanol inhibition of Sprague-Dawley rat brain Na + K-ATPase activity was examined in selected experiments for direct comparison with the results obtained using mouse brain. Ethanol (250-2000 mM) inhibited all ATPase activities in a concentration-dependent manner. In each case the IC50 was well beyond what would be a lethal concentration in vivo. Ethanol inhibition of mouse forebrain Na + K-ATPase activity was competitive with regards to K+ ion concentration, but was uncompetitive for inhibition of Mg-ATPase and Ca-ATPase activities. Norepinephrine (0.1 mM) did not sensitize mouse brain Na + K-ATPase activity to ethanol-induced inhibition. In contrast, norepinephrine sensitized rat brain Na + K-ATPase to ethanol inhibition when tested simultaneously with mouse brain under identical conditions. These results cannot be explained by differences in assay conditions and suggest that the interaction between norepinephrine and ethanol inhibition of Na + K-ATPase activity may be species specific. Norepinephrine alone stimulated mouse and rat brain Na + K-ATPase activity when assayed in imidazole buffer, but not when assayed in tris buffer. Furthermore, 0.1 mM norepinephrine slightly antagonized the inhibitory effect of ethanol on mouse brain Mg-ATPase activity, but did not affect ethanol-induced inhibition of Ca-ATPase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature dependence of ethanol depression in rats

The relationship between ambient temperature, body temperature, and brain sensitivity to ethanol was investigated in rats. Drug naive male Long Evans rats were injected IP with a hypnotic dose of ethanol (2.75 g/kg, 20% w/v). Immediately after injection, separate groups were exposed to one of five ambient temperatures from 12 to 34 degrees C. Ambient temperature significantly affected wake-up rectal temperature, sleep-time, and wake-up brain ethanol concentration. Sleep-times in individual rats increased 387% (from 24.0 min at 12 degrees C to 116.8 min at 34 degrees C) and wake-up brain ethanol concentrations decreased 79% (from 3.6 mg/g at 12 degrees C to 2.3 mg/g at 34 degrees C) as body temperatures increased from 35 to 41 degrees C. In addition, wake-up rectal temperatures were significantly, positively correlated with sleep-times (r = 0.32, P less than 0.05) and significantly, negatively correlated with wake-up brain ethanol concentrations (r = -0.49, P less than 0.01), further suggesting that brain sensitivity to ethanol increases as body temperature increases. These results are consistent with previous findings in mice, fit membrane perturbation theories of anesthesia, and indicate that temperature dependence of ethanol sensitivity is a general phenomenon extending across species. In conjunction with previous findings, the results also suggest that body temperature during intoxication may participate in mediating species differences in ethanol sensitivity.

Ethanol withdrawal in mice precipitated and exacerbated by hyperbaric exposure

Mice were fed an ethanol-containing liquid diet for 9 days. On removal of the diet, exposure to 12 atmospheres absolute of a mixture of helium and oxygen precipitated earlier withdrawal, increased withdrawal scores for the first 6 hours, and increased the peak withdrawal intensity compared to dependent animals exposed to control conditions. The enhanced withdrawal did not appear to reflect alterations in ethanol elimination, oxygen or helium partial pressures, body temperature, or general excitability. These results extend to chronically treated animals the evidence that hyperbaric exposure antagonizes the membrane actions of ethanol.

Temperature dependence of ethanol depression: linear models in male and female mice

The relationship between body temperature and ethanol sensitivity was studied in male and female mice. Age-matched drug-naive mice of both sexes were injected with 3.6 g/kg ethanol (20% w/v) and placed into a chamber kept at one of 8 designated temperatures from 13 to 36 degrees C. In both sexes, wake-up rectal temperatures were significantly, positively correlated with chamber temperatures and sleep-times and were significantly, negatively correlated with wake-up brain and blood ethanol concentrations. Linear regression analyses indicated that wake-up temperature accounted for up to 71% of the variability in sleep-times and wake-up ethanol concentrations in these mice. Similar relationships were found when the change in body temperature from baseline (delta T) was substituted for wake-up rectal temperature. Adding body weights and baseline temperatures did not improve the predictive ability of linear models based on wake-up rectal temperature alone. The results support the contention that body temperature represents an important determinant of ethanol sensitivity in both sexes. These findings provide additional evidence that ethanol sensitivity varies with body temperature in accordance with membrane perturbation theories of anesthesia.

Temperature modulates ethanol sensitivity in mice: generality across strain and sex

Findings in our laboratory indicate that body temperature alters ethanol potency as measured by sleep-time, wake-up brain ethanol concentration and mortality in male C57BL/6J mice. The current studies tested the generality of these results. Experiment one tested age-matched, drug-naive, male C57BL/6S and BALB/cS mice. Experiment two tested age-matched, drug-naive, male and female C57BL/6J mice. Each mouse was injected IP with 3.6 g/kg ethanol (20% w/v). After losing its righting reflex, the mouse was placed into a v-shaped sleep tray within a chamber kept at a designated temperature from 12 to 36 degrees C. Upon awakening, rectal temperature was measured and blood and brain samples were taken for gas chromatographic analysis. As in previous studies, ambient temperature modulated the body temperatures and sleep-times of intoxicated animals. More important, wake-up rectal temperatures were positively correlated with sleep-times and negatively correlated with wake-up ethanol concentrations in all animals tested. These results support the hypothesis that brain sensitivity to ethanol depression varies with body temperature in accordance with membrane perturbation theories of anesthesia.

Reduced lethality from ethanol or ethanol plus pentobarbital in mice exposed to 1 or 12 atmospheres absolute helium-oxygen

The present experiments investigated the effects of 1 and 12 atmospheres absolute (ATA) helium-oxygen on potentially lethal doses of ethanol given alone or in combination with pentobarbital. Drug-naive, male C57BL/6J mice were injected IP with 5.4-6.5 g/kg ethanol, 4.5-6.9 g/kg ethanol plus 20 mg/kg pentobarbital, or 50-110 mg/kg pentobarbital plus 2.5 g/kg ethanol. Following injection, the mice were placed into chambers and exposed to environments of 1 ATA air, 1 ATA helium-oxygen, or 12 ATA helium-oxygen. Exposure to 1 or 12 ATA helium-oxygen significantly reduced the lethal effect (percent mortality at given doses and LD50) of ethanol given alone or with 20 mg/kg pentobarbital when compared to animals exposed to 1 ATA air. The pattern and degree of reduction in lethality for the 1 and 12 ATA helium-oxygen treatments were similar, suggesting that the antagonism resulted from increased helium or decreased nitrogen and not from increased atmospheric pressure. Exposure to these environments did not reduce lethality in mice given 2.5 g/kg ethanol in combination with relatively high doses (50-110 mg/kg) of pentobarbital. These findings suggest that helium-oxygen breathing mixtures may be useful in the treatment of some overdose patients.

Effect of norepinephrine on inhibition of mouse brain (Na+ + K+)-stimulated, (Mg++)-dependent, and (Ca++)-dependent ATPase activities by ethanol

Norepinephrine (0.1 mM) has been reported to "sensitize" (Na+ + K+)-ATPase activity of rat brain homogenates to inhibition by ethanol. The present study extends these investigations to the mouse and includes other ATPase activities. We measured the effects of norepinephrine on the sensitivity of ethanol-induced inhibition of (Na+ + K+)-stimulated (E.C. 3.6.1.3), (Mg++)-dependent (E.C. 3.6.1.4) and (Ca++)-dependent ATPase activities. Whole forebrains from C57BL/6J mice were homogenized and assayed in vitro for ATPase activity using standard conditions. Ethanol (0.125-2.0 M) caused a dose-dependent inhibition of all three ATPases. Norepinephrine (0.1 mM) had no appreciable effect on ethanol's inhibition of (Na+ + K+)-stimulated or (Ca++)-dependent ATPase activities, but slightly antagonized ethanol's effect on (Mg++)-ATPase. These results suggest that norepinephrine has little effect on the sensitivities of specific ATPases to ethanol inhibition in mouse brain.

Temperature dependence of ethanol depression in C57BL/6 and BALB/c mice

The relationship between environmental temperature, body temperature and brain sensitivity to ethanol was investigated in male C57BL/6S and BALB/cS mice. Age-matched, drug-naive mice of both strains were injected with 3.6 g/kg ethanol (20% w/v) and placed into a chamber kept at one of eight designated temperatures from 12 to 36 degrees C. Chamber temperature significantly affected wake-up rectal temperatures, sleep-times and wake-up brain ethanol concentrations in the intoxicated mice. Wake-up rectal temperatures were significantly, positively correlated with sleep-times and significantly, negatively correlated with wake-up brain ethanol concentrations in both strains. Linear regression analyses indicated that up to 47% of the variability in ethanol sensitivity of C57 mice and up to 31% of the variability in sensitivity of BALB mice could be accounted for by their wake-up rectal temperatures suggesting that the effects of ambient temperature on ethanol sensitivity were mediated, in part, by the resultant body temperatures. These results replicate and extend previous findings and demonstrate that temperature dependence of ethanol depression is not strain specific. The correlational and regression analyses provide additional evidence that brain sensitivity to ethanol depression varies with body temperature in accordance with membrane perturbation theories of anesthesia.

The importance of experience in the development of tolerance to ethanol hypothermia

Studies were conducted to determine if an animal has to experience a reduction in body temperature during the acquisition period in order to develop tolerance to the hypothermic effect of ethanol. Adult, drug-naive C57BL/6J mice were injected with 2.6 or 3.6 g/kg ethanol or normal saline once daily for 6 days. During the tolerance acquisition period, days 1-5, mice were placed into warmed chambers (36 +/- 2(0)C) which offset ethanol hypothermia or into chambers at room temperature (24 +/- 1(0)C). On day 6, all mice were injected with ethanol and placed into chambers at room temperature. Tolerance to ethanol's hypothermic effect did not develop in the ethanol-warm acquisition group. These mice had a significantly greater degree of hypothermia on test day than the ethanol-room temperature acquisition group, which showed tolerance, and their degree of hypothermic response was similar to that of mice injected with saline during acquisition. The differences between groups cannot be attributed to pharmacokinetic alterations or to conditioned responses since there were no differences between groups in blood or brain ethanol concentrations on test day and all groups were exposed to the same acquisition and test situations. These results extend previous work to suggest that the development of tolerance to the physiological, as well as behavioral, aspects of ethanol intoxication requires more than simple exposure to ethanol.

Temperature dependence of ethanol lethality in mice

The present study provides systematic evidence indicating a direct relationship between environmental temperature, rectal temperature and ethanol lethality. Male, C57 BL/6J mice, previously housed at room temperature (23 +/- 1 degree C), were injected intraperitoneally with 4.8 to 9.2 g kg-1 ethanol and then exposed for 24 h to ambient temperatures that did not appreciably exceed the thermally neutral range for sober mice (20 to 35 degrees C). There was a direct relationship between temperature and ethanol lethality at 8 and 24 h after injection. The 8 h LD50 increased by 64%, from 5.3 to 8.7 g kg-1, as environmental temperature decreased from 35 to 20 degrees C. The 24 h LD50 increased by 51%, from 5.3 to 8.0 g kg-1, across this temperature range. Each 5 degrees C reduction in ambient temperature induced a significant decrease in the rectal temperature of ethanol-injected mice. Mean rectal temperature ranged from 2.2 degrees C above baseline at an ambient temperature of 35 to 15 degrees C below baseline in the 20 degrees C environment. Ethanol induced a significant dose-related hypothermia in mice exposed to the 20, 25 and 30 degrees C environments but did not produce hypothermia in animals kept in the 35 degrees C environment. These findings indicate that the potency of potentially lethal ethanol doses varies with body temperature in accordance with partition and membrane expansion-fluidization theories of anaesthesia.

Lesion-Induced Sprouting in the Rat Dentate Gyrus Is Inhibited by Repeated Ethanol Administration

The effect of ethanol on hippocampal axonal sprouiting was studied with a histochemical technique for identifying acetylcholinesterase. Unilateral lesion of the entorhinal cortex in adult rats produced an increase in the density of acetylcho-linesterase staining in the outer molecular layer and a concomitant increase in the width of the pale-staining commissural-associational zone of the dentate gyrus. Other rats were given ethanol (11.3 +/- 0.45 grams per kilogram) for 2 weeks before and 9 days after receiving the lesion. Ethanol abolished the expansion of the commissural-associational zone. The effect of ethanol on sprouting axons suggests that it may inhibit recovery of function after brain injury.

Lesion-induced sprouting in the rat dentate gyrus is inhibited by repeated ethanol administration

The effect of ethanol on hippocampal axonal sprouting was studied with a histochemical technique for identifying acetylcholinesterase. Unilateral lesion of the entorhinal cortex in adult rats produced an increase in the density of acetylcholinesterase staining in the outer molecular layer and a concomitant increase in the width of the pale-staining commissural-associational zone of the dentate gyrus. Other rats were given ethanol (11.3 +/- 0.45 grams per kilogram) for 2 weeks before and 9 days after receiving the lesion. Ethanol abolished the expansion of the commissural-associated zone. The effect of ethanol on sprouting axons suggests that it may inhibit recovery of function after brain injury.

Interaction of apomorphine and amantadine with ethanol in men

Male moderate drinkers (n = 12) drank ethanol (0.8 g/kg) and then ingested one of the following: apomorphine (5 mg), amantadine (200 mg), or placebo. Subjects were tested on a battery of physiological and behavioral measures using a double-blind, within-subjects, crossover design. Postethanol ingestion of apomorphine significantly increased ethanol's effect on 3 out of the 8 measures employed (divided attention, objective and subjective inebriation ratings) without significantly altering blood ethanol concentrations or the rate of blood ethanol decline. There was no indication that apomorphine antagonized ethanol's effects. In contrast to reports indicating that amantadine antagonized ethanol depression in rodents, amantadine did not significantly alter the degree of ethanol intoxication in humans. The increase in intoxication induced by apomorphine supports suggestions that dopaminergic systems may be involved in mediating ethanol intoxication and that the sobering effect of catecholamine-augmenting drugs results from noradrenergic, rather than combined noradrenergic and dopaminergic, stimulation. Further studies are necessary to elucidate the role of pre- and postsynaptic dopaminergic receptors in mediating these effects.

Hyperbaric ethanol antagonism: role of temperature, blood and brain ethanol concentrations

Three studies investigated the mechanism of hyperbaric ethanol antagonism. C57 Bl/6j mice were injected intraperitoneally with 3.6 g/kg ethanol and were exposed to 1-12 atmospheres absolute (ATA) helium-oxygen or to 1 ATA air at temperatures that offset the cooling effects of helium or helium and ethanol. Hyperbaric treatment significantly reduced sleep-time and increased wake-up brain ethanol concentrations compared to temperature matched controls. Treatment with 12 ATA helium-oxygen increased the brain ethanol concentration and the brain-blood ethanol ratio at 150 minutes after ethanol administration. These results exclude helium or pressure-induced changes in body temperature, rate of blood ethanol decline or distribution to the brain as mechanisms mediating the antagonism. The data support a membrane site of antagonism.