Ethanol-induced hypothermia and biogenic amine metabolites

Ethanol is known to cause hypothermia. The rectal temperature of rats receiving ethanol, 4 g/kg i.p., at an ambient temperature of 23 degrees C decreased by 2 degrees C. This body temperature decrease could be prevented by keeping the animals at an ambient temperature of 34 degrees C. Irrespective of the body temperature it was found that the concentration of the major metabolites of dopamine and serotonin in brain tissue was significantly increased. Thus, the change in brain monoamine metabolite levels in rats after administration of ethanol are not due to ethanol-induced hypothermia.     

Drug interactions with ethanol. Effects on body temperature and motor impairment

Single doses of d-amphetamine, chlorpheniramine or diazepam were combined with ethanol under two conditions: (i) in drug-naive mice and (ii) in mice which had been given a single dose of ethanol 72 hr previously. Ethanol was administered orally at doses of 6.0, 3.0 or 1.5 g/kg; doses of d-amphetamine, chlorpheniramine or diazepam were given intraperitoneally. Three parameters were measured; changes in rectal temperature, forced motor coordination, as evaluated by rotarod performance and concentrations of ethanol in blood. d-Amphetamine and chlorpheniramine attenuated the hypothermia induced by ethanol but had no effect on the motor-impairing effect of ethanol. Hypothermia induced by diazepam was unaffected by ethanol, but the combination appeared to impair maximally rotarod performance. Concentrations of ethanol in blood did not differ between ethanol-naive mice and mice which had received the same dose of ethanol 72 hr previously. Changes in body temperature and intoxication have been attributed to central actions of ethanol; however, the differential results obtained from the interactions between these drugs suggest differing sensitivities of the various systems which are affected by ethanol.     

Effects of methamphetamine and methyldopa on ethanol induced hypothermia in mice

The effects of D-methamphetamine HCl (1, 2 and 4 mg/kg, i.p.) and alpha-methyldopa (1, 2 and 4 mg/kg, i.p.) on rectal temperature and on ethanol (3 g/kg, i.p.)-induced hypothermia have been investigated in mice. Methamphetamine caused a dose-dependent hyperthermia, but methyldopa induced hypothermia, which decreased with increases in dose. Methamphetamine antagonized the hypothermic effect of ethanol, but methyldopa (1 and 2 mg/kg) did not affect it. Methyldopa (4 mg/kg), however, reversed ethanol hypothermia. Ethanol pretreatment significantly potentiated the hypothermic effect of methyldopa (4 mg/kg), and it prevented methamphetamine-induced hyperthermia. A possible central action for the tested drugs on biogenic monoamines and a peripheral component in their thermoregulatory effects are discussed in this report.     

Ethanol-mediated inhibition of mitogen-activated protein kinase phosphorylation in mouse brain

Ethanol (1.5-3.5 g/kg body weight) was administered intraperitoneally to mice and the phosphorylation of MAP (mitogen-activated protein) kinase in the cerebral cortex was determined using phospho-specific MAP kinase antibodies. Ethanol inhibited the phosphorylation of MAP kinase in a dose- and time-dependent manner. Developmental studies demonstrated that the levels of phospho-MAP kinase increased from fetal cortex (prenatal) to 16-day-old mice (postnatal) and remained constant up to 4 months of age. However, ethanol (3.5 g/kg) decreased the phospho-MAP kinase staining in all of the age groups studied. Subcellular fractionation studies demonstrated that ethanol inhibited the phosphorylation of MAP kinase in both the cytosol as well as nucleus, but did not alter the levels of MAP kinase. Likewise, MK-801 (0.4 mg/kg) or flurazepam (75 mg/kg) also decreased the phospho-MAP kinase content. These data indicate that ethanol may inhibit the phosphorylation of MAP kinase in vivo by either inhibiting NMDA receptors or activating GABA receptors.     

Conditioned and unconditioned influences on body temperature and ethanol hypothermia in laboratory rats

Both a naive group and a group of chronically handled rats were observed to develop hyperthermia when their cages (rats in situ) were removed from their usual positions on cage rack shelving and placed upon the laboratory bench for a period of 60 minutes. That procedure apparently functioned as a stressful unconditioned stimulus for the naive group. The extent of hyperthermia was more pronounced in the chronic group, presumably owing to the classical conditioning of environmental cues to the stressful events that had repeatedly been associated in the past with placement of the cage onto the benchtop. Doses of naloxone (10 mg/kg) and of ethanol (1 g/kg) that normally produced negligible effects on body temperature were found to significantly reduce the hyperthermia that developed when cages were placed onto the benchtop. The hypothermic response to 2 g/kg of ethanol was lessened in both groups by placement of the cages onto the benchtop.     

Hypothalamic catecholamines and tolerance for severe cold in ethanol-treated guinea-pigs.

1 The effect of ethanol (2g/kg) on hypothalamic catecholamines in guinea-pigs kept at room temperature (20 degrees C) and in severe cold (-20 degrees C) for 1.5 h was determined. Serum glucose, triacyl-glycerols and free fatty acids (FFAs), glycogen in liver and skeletal muscle and total lipid and triacyglycerols in the interscapular adipose tissue were also determined. 2 Ethanol increase the noradrenaline and adrenaline content of the hypothalamus at 20 degrees C and reduced ther rectal temperature by about 2 degrees C. The hypothalamic noradrenaline content of the ethanol-treated guinea-pigs exposed to cold, in which the fall in rectal temperature was about 8 degrees C, was higher than in the controls, whose rectal temperature decreased only by about 2 degrees C. 3 Cold exposure increased FFA concentration in serum and reduced skeletal muscle glycogen and serum glucose concentrations in both groups, but no significant differences were found in the carbohydrate and lipid values between the groups at -20 degrees C. 4 It is possible that the diminished cold tolerance in the ethanol-treated guinea-pigs might be due, at least in part, to the effect of ethanol on the catecholamines in the hypothalamus.     

Brain temperature and ethanol sensitivity in C57 mice: a radiotelemetric study

This study investigated the relationship between ethanol sensitivity and brain temperature using radiotelemetric techniques. Radiotelemetric brain probes were implanted in the lateral cerebral ventricle of C57BL/6 mice. Rectal and brain temperatures, duration of loss of righting reflex (LORR), and blood and brain ethanol concentrations at the return of righting reflex (RORR) were measured following intraperitoneal (IP) injection with 3.6 g/kg ethanol and exposure to 12, 15, 22 or 34 degrees C. Rectal and brain temperatures were significantly correlated in untreated and intoxicated mice. Brain temperatures were lower than rectal temperatures in untreated mice, but were not different than rectal temperatures in intoxicated mice. Ethanol sensitivity, measured by the duration of LORR and ethanol concentrations at RORR, was significantly correlated with brain as well as rectal temperatures at RORR. Brain probe implantations did not significantly affect ethanol sensitivity. The direct positive relationship between brain temperature and ethanol sensitivity in C57 mice fits predictions based on membrane actions of ethanol and supports the hypothesis that temperature-induced changes in behavioral sensitivity to ethanol are mediated through changes in brain membrane temperature.     

Regional rat brain content of adenosine 3',5'-cyclic monophosphate and guanosine 3',5'-cyclic monophosphate after acute and subacute treatment with ethanol

Acute administration of ethanol (1.0, 2.0, and 5.0 g/kg, ip) to naive male rats (Sprague-Dawley) caused a dose-dependent depression of cerebellar guanosine 3′,5′-cyclic monophosphate (cGMP), and a reduction in cortical cGMP at the highest dose of ethanol. The cGMP content was not altered in the anterior hypothalamus, posterior hypothalamus, or striatum. On examining adenosine 3′,5′-cyclic monophosphate (cAMP) levels, only the area of the striatum was reduced (5.0 g/kg, ethanol). In these acute experiments there was a negative correlation between blood ethanol concentrations and body temperatures. An elevated environmental temperature (31 ± 1°C) to prevent hypothermia from ethanol administration indicated that hypothermia was not a contributory factor. In the subacute experiments animals showed at the end of 24 hr of ethanol inhalation less hypothermia than naive animals with similar blood ethanol concentrations, a reduction in cGMP in the cerebellum and cortex, but no alteration in regional brain cAMP. When the animals were injected with ethanol (2.0 g/kg, ip) 48 hr after removal from the chamber (ethanol vapor, 24 hr), ethanol produced no significant reduction in body temperature (tolerance), but a decrease in cerebellar cGMP. The cAMP content of the tissues was similar to control animals. Ethanol administration (2.0 g/kg, ip) 48 hr later to animals which were previously exposed to air only in the chamber (24 hr) demonstrated a reduction in body temperature as compared with tolerant animals, a decrease in cerebellar cGMP, and no depletion of cAMP in regional sections of the brain. From this in vivo study the data seem to suggest that brain cyclic nucleotides, particularly cAMP, may have a limited role in ethanol-induced intoxication and tolerance to the hypothermic effect of ethanol.     

Effects of ethanol on body temperature of rats at high ambient pressure

Separately, ethanol and high ambient pressure cause hypothermia in laboratory animals. However, ethanol and high pressure have mutually antagonistic effects on several biological functions and the present experiments investigate their combined action on body temperature. Rats given saline, 1.5 g/kg ethanol or 3.5 g/kg ethanol were exposed to 1 bar air at 25-26 degrees C, 1 bar helium-oxygen at 30-31 degrees C, or 48 bar helium-oxygen at 33.5-34.5 degrees C. Ambient, colonic and tail-skin temperatures were monitored for 60 min. There were no significant differences in mean ambient or tail-skin temperatures between groups belonging to the same ambient condition. Colonic temperatures under the 1 bar conditions were 1.5-2 degrees C lower in the 3.5 g/kg ethanol group than in the saline and 1.5 g/kg ethanol groups, while no significant differences were observed between the groups at 48 bar. Comparisons of the colonic temperatures at the end of the observation period, i.e., 60 min after administration of ethanol, demonstrated that their values at 48 bar were significantly lower than at 1 bar after saline, significantly higher after 3.5 g/kg ethanol and identical across conditions in the 1.5 g/kg groups. The results suggest that high ambient pressure may counteract rather than potentiate the hypothermic effect 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.     

Effect of exogenous selenium on the testicular toxicity induced by ethanol in rats

The effects of supplementation of selenium at a dose of 10 microg/ kg body weight were investigated on ethanol induced testicular toxicity in rats. In the present study, four groups of male albino rats were maintained for 60 days, as follows: (1) Control group (normal diet) (2) Ethanol group (4g/kg body weight) (3) Selenium (10 microg/kg body weight) (4) Ethanol + Selenium (4g/kg body weight + 10 microg/kg body weight). Results revealed that ethanol intake caused drastic changes in the sperm count, sperm motility and sperm morphology. It also reduced the levels of testosterone and fructose. The activities of 3betaHSD, 17betaHSD in the testis and SDH in the seminal plasma were also reduced. Lipid peroxidation was also enhanced as the lipid peroxidation products were increased and the activities of the scavenging enzymes were reduced. But on coadministration of selenium along with alcohol all the biochemical parameters were altered to near normal levels indicating a protective effect of selenium. These results were reinforced by the histopathological studies.     

Antagonism of the stimulant and depressant effects of ethanol in rats by naloxone

The action of naloxone (0.5 and 2 mg/kg IP) on the behavioural effects of a low (2 g/kg PO) and a high dose (4 g/kg PO) of ethanol was studied in rats. Ethanol at the low dose increased spontaneous motility, enhancing open-field external ambulations and reducing shuttle-box latency. All these effects were antagonized by naloxone. Ethanol at the high dose produced hypomotility, decreasing open-field external ambulations and impairing shuttle-box performance. In this case, naloxone also reduced the ethanol effect, but its action was less consistent. Therefore, although mechanisms other than a specific opioid receptor blockade by naloxone must be considered, an involvement of opioid peptides in the effects of ethanol cannot be discounted.     

The effect of ethanol on behavioral temperature regulation in mice

Mice were injected with 20% ethanol in 0.9% NaCl, or with 0.9% NaCl without ethanol during sessions of behavioral thermoregulation in a tubular temperature gradient (ambient temperature range approximately 9-38 degrees C). Internal temperature was monitored with an implanted telemetry device. An imaging system recorded the position (selected temperature) of the mouse within the gradient every 5 sec. A dose of either 2.25 or 2.60 g ethanol/kg body wt. produced significantly lower body temperatures than control (NaCl) injections. The 2.60 g/kg dose produced significantly lower selected temperatures than either the NaCl or 2.25 g/kg injections. Doses of 2.75 g ethanol/kg and above incapacitated the mice, precluding accurate behavioral thermoregulation. Utilizing a thermoregulatory index to compare the responses following experimental and control injections indicated that 2.25 or 2.60 g ethanol/kg leads to a decrease in the regulated temperature of mice.     

Transient induction of hepatic metallothionein following oral ethanol administration

Chronic ethanol ingestion has been associated with alterations of zinc homeostasis. Various treatments that alter zinc disposition induce hepatic metallothionein (MT). Therefore, this study was performed to determine the effect of acute ethanol exposure on hepatic MT levels. Adult male CF-1 mice were administered ethanol intragastrically and their hepatic MT was quantified at various times thereafter by the Cd-radioassay method. Ethanol (5 g/kg, ig) produced significant increases in hepatic MT as early as 4 hr after dosing. Maximal hepatic MT concentrations (19-fold increase) were observed 24 hr after ethanol and returned to control concentrations by 48 hr. Hepatic MT levels were increased 24 hr after 5 or 7 g ethanol/kg but were not altered by 1, 2, or 3 g/kg. Elevations in pancreatic MT, but not in renal or intestinal MT, also occurred 24 hr after ethanol (5 g/kg). Actinomycin D (1.25 mg/kg, ip) prevented the increase in hepatic MT produced by ethanol, whereas inhibition of ethanol oxidation by pyrazole (150 mg/kg, ip) did not prevent the induction of hepatic MT. Gel filtration chromatography and uv spectral analysis confirmed the presence of MT in the livers of ethanol-treated mice. These data show that acute ethanol administration produces a marked elevation of hepatic MT that is transient.     

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.     

Hypoglycemia and hypothermia induced by ethanol: antagonism by indomethacin

The influence of pretreatment with 5.0 or 10.0 mg/kg of indomethacin, a prostaglandin synthetase inhibitor, on the alterations in body temperature produced by 3.0 and 4.0 g/kg of ethanol, was studied in food-deprived and free-feeding rats. A partial antagonism of ethanol's hypothermic effect resulted from indomethacin pretreatments and this effect was found to be ethanol dose-dependent. This result could account for the conflicting reports in the literature on the effectiveness of indomethacin in antagonizing ethanol-induced hypothermia. Indomethacin (5.0 mg/kg) also antagonized ethanol-induced hypoglycemia in 48 hr starved rats. The relationship between two effects of ethanol, hypothermia and hypoglycemia, is discussed.     

Effects of lorazepam on the properties of brain polysomes.

This study determined the effects of acute administration of lorazepam (LRZ) on brain protein synthesis by examining the translational abilities of polysomal RNA under in vitro conditions compared to those produced by the CNS depressants, ethanol and pentobarbital. Lorazepam (2 mg/kg body weight), ethanol (4 g/kg body weight) or pentobarbital (40 mg/kg body weight) were given orally to 6-week old male Sprague-Dawley rats. Control groups were either untreated or received the vehicle sesame seed oil orally. The measurement of rectal temperature in each group before (baseline) and 60 min after drug administration showed no change in body temperature in the control or LRZ treated groups but there was a significant temperature drop in the ethanol and pentobarbital group. After 60 min of drug administration, experimental groups when compared to the controls showed significant inhibitions in the translational activities of the cerebral polysomes. The inhibition was most pronounced with polysomes from the LRZ treated group and was consistently observed over a 60 min time period. The findings suggest polysomal translation as one of the major sites of action of LRZ which is independent of changes in body temperature as compared to ethanol and pentobarbital. Since protein synthesis is known to play a key role in learning and memory, the observed inhibitory effects of LRZ may explain its interference with memory consolidation observed under experimental and clinical conditions.     

In utero alcohol heightens juvenile reactivity

The behavioral teratogenicity of ethanol was studied in a laboratory model of the fetal alcohol syndrome. Pregnant rats were placed in one of three groups: Ethanol (4 g ethanol/kg intubated twice daily; Purina Chow ad lib.); Sucrose (7 g sucrose/kg intubated instead of ethanol; Untreated (no intubations; Purina Chow ad lib.). Ethanol offspring did not differ from either control group in neonatal body weight or developmental measures. On Day 35, 2 female offspring per litter were tested for reactivity to acoustic startle stimuli. Activity was measured during the pre-stimulus foreperiod and during inter-stimulus intervals. Ethanol pups displayed heightened startle reactivity in the absence of hyperactivity or disrupted habituation. These data indicate that ethanol in utero produces hyperrectivity in the absence of morphological, body weight or developmental abberations.     

Effects of the acute administration of ethanol on the sleep of the rat: a dose-response study.

Seven-hr sleep recordings were performed on rats following intraperitoneal injection of saline or one of four doses of ethanol (1.1, 1.5, 2.0 or 2.5 g/kg). Total minutes of REM sleep and percentage REM sleep were decreased in a dose-dependent manner. Percentage nonREM sleep increased with progressively higher doses. The decrease in REM sleep appeared to be related to a decrease in the number of REM sleep episodes and an increase in the length of the REM-nonREM cycle. Other variables such as mean length of REM sleep episodes and REM sleep efficiency were unchanged. An analysis of the first and second 3.5 hr of the recording showed that ethanol continued to have marked effects on REM and nonREM sleep during the second 3.5 hr, when blood levels were declining. Ethanol produced decreases in sleep latency, but total sleep time was unchanged.     

Protective action of carnitine on liver lipid metabolism after ethanol administration to rats.

Ethanol administration to rats causes a significant increase in colonic temperature 18 hr after drug administration. Carnitine administration to such animals did not significantly decrease that temperature. Carnitine gave some protection against increases in SGOT levels in animals receiving ethanol. This protective action was independent of its effect on liver lipids. Carnitine significantly lowered blood triglycerides, but this action occurred with both normal rats and rats receiving alcohol. Higher amounts of carnitine (0.5 mg/g of body weight rat) produced a significant decrease in the liver triglycerides. This effect was more marked in animals receiving ethanol than in control rats. Carnitine also showed a significant lipotropic action which was reflected in a diminution of the total lipid content in liver. Again, the effect was more marked in animals receiving ethanol than in controls.