Body temperature influences on ethanol elimination rate

Individual Differences in Ethanol Drinking and Seeking Behaviors in Rats Exposed to Chronic Intermittent Ethanol Vapor Exposure is Associated with Altered CaMKII Autophosphorylation in the Nucleus Accumbens Shell

Chronic intermittent ethanol vapor exposure (CIE) in rodents produces reliable and high blood ethanol concentration and behavioral symptoms associated with moderate to severe alcohol use disorder (AUD)—for example, escalation of operant ethanol self-administration, a feature suggestive of transition from recreational to addictive use, is a widely replicated behavior in rats that experience CIE. Herein, we present evidence from a subset of rats that do not demonstrate escalation of ethanol self-administration following seven weeks of CIE. These low responders (LR) maintain low ethanol self-administration during CIE, demonstrate lower relapse to drinking during abstinence and reduced reinstatement of ethanol seeking triggered by ethanol cues when compared with high responders (HR). We examined the blood ethanol levels in LR and HR rats during CIE and show higher levels in LR compared with HR. We also examined peak corticosterone levels during CIE and show that LR rats have higher levels compared with HR rats. Lastly, we evaluated the levels of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) in the nucleus accumbens shell and reveal that the activity of CaMKII, which is autophosphorylated at site Tyr-286, is significantly reduced in HR rats compared with LR rats. These findings demonstrate that dysregulation of the hypothalamic–pituitary–adrenal axis activity and plasticity-related proteins regulating molecular memory in the nucleus accumbens shell are associated with higher ethanol-drinking and -seeking in HR rats. Future mechanistic studies should evaluate CaMKII autophosphorylation-dependent remodeling of glutamatergic synapses in the ventral striatum as a plausible mechanism for the CIE-induced enhanced ethanol drinking and seeking behaviors.

Genetic studies of acute tolerance, rapid tolerance, and drinking in the dark in the LXS recombinant inbred strains

BACKGROUND

We hypothesized that rapid tolerance (1-day tolerance) for the duration of the loss of righting reflex ("sleep time" [ST]) was mediated by an increase in acute functional tolerance (AFT). We also hypothesized that increased AFT would correspond to increased drinking. These questions were addressed using the LXS recombinant inbred mouse strain panel.

METHODS

Mice were given a pretreatment dose of either saline or 5 g/kg alcohol on day 1. On day 2, mice were tested for ST (4.1 g/kg) using a method with which it is possible to accurately assess AFT. Genetic correlation analysis was conducted among the ST-related variables and also with "drinking in the dark" (DID) which was previously measured by Saba and colleagues (2011).

RESULTS

Saline-pretreated mice showed a continuous distribution of ST ranging from ~40 minutes to over 3 hours. Of the 43 strains tested, 9 showed significantly decreased ST after alcohol pretreatment, while in 3 strains, ST was significantly increased. AFT scores ranged from 0 to over 200 mg% in the saline group, and in the alcohol group, 8 strains showed a significant increase in AFT and 2 strains showed significant decrease in AFT. In the saline group, AFT was significantly correlated with ST (r = -0.47), but not in the alcohol group (r = -0.22). DID was significantly correlated with only AFT in the alcohol pretreated group (r = 0.64).

CONCLUSIONS

The results suggest that AFT is an important component of the overall ST response, but that the alcohol pretreatment-induced change in AFT does not contribute to rapid ST tolerance. The significant correlation between DID and AFT in the alcohol group suggests that AFT may be a more relevant predictor of drinking behavior than the static measurement of ST. Moreover, preexposure to alcohol seems to change AFT in a way that makes it an even stronger predictor of drinking behavior.

Genetic Dissociation Between Ethanol Sensitivity and Rapid Tolerance in Mouse and Rat Strains Selectively Bred for Differential Ethanol Sensitivity

BACKGROUND

The Inbred Long- and Short-Sleep mice (ILS and ISS) and the Inbred High- and Low-Alcohol-Sensitive rats (IHAS and ILAS) were selectively bred for differential alcohol sensitivity with use of the duration of loss-of-righting-reflex test (LORR), with the IHAS and ILS animals being much more sensitive than the ILAS and ISS animals, respectively. The current study was undertaken to determine whether acute sensitivity in these strains is genetically correlated to a rapid tolerance to alcohol, a form of tolerance that is evident 24 hr after a single alcohol dose.

METHODS

Separate groups of animals were administered a single pretreatment dose of alcohol (0-6 g/kg for the mice; 0-4 g/kg for the rats). Alcohol sensitivity was tested 24 hr later with the LORR test, and blood ethanol concentration was tested at regain of righting (BECRR). Alcohol-induced hypothermia also was determined in the mice. Independently derived replicate rat strains were used for all experiments (IHAS1, ILAS1; IHAS2, ILAS2); no such replicates exist for the ILS and ISS strains.

RESULTS

Alcohol pretreatment caused a dose-dependent decrease in LORR duration accompanied by an increase in BECRR in the ILS strain, but LORR increased in the ISS strain with no effect on BECRR. Both strains became hypothermic during the LORR test on day two, but the only significant effect of alcohol pretreatment was in the ISS strain, in which alcohol-induced hypothermia was enhanced. Alcohol pretreatment caused a significant dose-dependent decrease in LORR duration accompanied by an increase in BECRR in the IHAS1 but not in the IHAS2 strain. In contrast, ILAS1 and ILAS2 strains both showed a significant increase in LORR duration and also a significant increase in BECRR.

CONCLUSIONS

Alcohol pretreatment caused a dose-dependent decrease in LORR duration and an increase in BECRR in the IHAS1 and ILS strain, suggesting the development of functional rapid tolerance. In contrast, LORR duration increased in the ILAS1, ILAS2, and ISS groups, but BECRR either increased (ILAS1, ILAS2) or did not change (ISS). These observations suggest that central nervous system sensitivity was decreased in the ILAS1 and ILAS2 groups (i.e., rapid functional tolerance) or unchanged in the ISS strain, but that some pharmacokinetic property also was altered in these strains. Overall, the results do not support a genetic relation between alcohol sensitivity and the development of rapid tolerance.

Short-term selection for the interaction between S-propranolol and ethanol in mice

BACKGROUND

We have previously demonstrated that there is an interaction between S-propranolol, a beta-adrenergic blocking agent, and ethanol on the hypnotic sensitivity of inbred short- and long-sleep mice (ISS and ILS). We found that the interaction was due to an additive hypothermic effect of ethanol and S-propranolol that markedly decreased the disappearance rate of ethanol. There was no discernible effect of S-propranolol on the hypnotic actions of ethanol as evidenced by the waking blood ethanol levels. Because ISS mice were more sensitive to this effect than were ILS mice, it seemed that there was a genetic effect to the response. Therefore, we carried out a short-term breeding project to determine whether the response could be selectively bred.

METHODS

We used the heterogeneous stock of mice from the Institute for Behavioral Genetics to carry out the selection study. The index for selection was the difference in sleep time between the same animal treated with propranolol and ethanol versus treatment with saline and ethanol at least 1 week apart.

RESULTS

In four generations, we were able to achieve separation between mice with a large difference in sleep time (high line) from those with a smaller difference in sleep (low line) time. There was no difference between the average blood ethanol at awakening in the high line versus the low line. The effect was not due to a difference in rate of propranolol metabolism between the two lines. Sleep time with ethanol alone was not different between the high and low lines.

CONCLUSIONS

The magnitude of the interaction between ethanol and S-propranolol is controlled by alleles with polymorphisms present in the HS stock of mice. The response is most likely due to a difference in the mechanisms of thermogenesis controlled by the beta-adrenergic receptors in muscle and fat. Because there were no sleep time differences between the high and low lines given ethanol alone, central nervous system sensitivity to ethanol is not a correlated response to the selection.

Interaction between S-propranolol and ethanol in mice selectively bred for ethanol sensitivity: the inbred short- and long-sleep mice

BACKGROUND

We have studied the effect of a beta-adrenergic blocking agent, S-propranolol, on the response of mice to anesthetic doses of ethanol. We used the selectively bred short and long sleep (ISS and ILS) mice. These mice were selected for their differential sensitivity to anesthetic doses of ethanol and then inbred. The study was prompted by the finding that the effect of ethanol on the firing rate of cerebellar Purkinje cells is modulated by beta-adrenergic input. In addition, this firing rate depression by ethanol is highly correlated with the anesthetic potency of ethanol. We were attempting to find a behavioral correlate of this effect of beta-adrenergic agents in the ISS and ILS mice.

METHODS

We studied the effect of S-propranolol plus ethanol on the sleep time and blood ethanol at awakening in the inbred ILS and ISS mice. We administered anesthetic doses of ethanol with and without S-propranolol. We conducted studies of the rate of disappearance of ethanol in the presence of S-propranolol and carried out sleep time and metabolic studies with mice in an incubator held at 32 to 33 degrees C.

RESULTS

We found that S-propranolol caused a prolonged anesthetic time brought about by ethanol but only in ISS mice. There was no significant difference in the blood ethanol levels at awakening with or without S-propranolol, indicating that S-propranolol had no effect on the brain sensitivity. Subsequently, we showed that this was due to a profound hypothermia caused by a combination of S-propranolol and ethanol. This was greater in the ISS mice because a larger dose of ethanol was required for the anesthetic effect of ethanol. The effect on ethanol disappearance rate, temperature drop, and anesthesia time all were largely reversed by placing the animals in an incubator at 32 to 33 degrees C.

CONCLUSIONS

Profound hypothermia lowers the ethanol disappearance rate when both S-propranolol and ethanol are given. The effect of S-propranolol is likely due to the blockade of beta-adrenergic receptors that prevents thermogenic responses to the hypothermia brought about by ethanol. The results indicated that there might be a genetic effect controlling the hypothermic response to the combination of S-propranolol and ethanol. Further experiments to investigate this are reported in a subsequent article. We could find no evidence of a central nervous system effect of S-propranolol on the hypnotic actions of ethanol in these strains of mice.

Ontogeny of ethanol elimination and ethanol-induced hypothermia

Ontogeny of ethanol elimination rates and ethanol-induced hypothermia were examined as possible mechanisms contributing to the marked reduction in ethanol sensitivity early in life (Little et al., 1996; Silveri & Spear, 1998) and the notable gender difference in ethanol sleep-time seen in adult animals (Silveri & Spear, 1998). Elimination rates and brain/blood ethanol levels were determined following doses of 1.5 or 4.5 g/kg ethanol in male and female Sprague-Dawley rats at postnatal days (P)16, 26, 36, or 56. Animals were sacrificed at 40, 80, or 160 min post-injection, with ethanol elimination rates estimated from the slope of the regression of blood and brain alcohol levels across the three sampling periods. P16 animals exhibited the slowest rate of ethanol metabolism, while no gender effects were evident at any age. Observed ontogenetic increases in ethanol hypothermia were not systematically related to the ontogeny of ethanol metabolism. Factors other than ontogenetic changes in ethanol metabolism, hypothermia, or the distribution of ethanol between brain and blood must underlie the relative insensitivity to ethanol often reported in young and adolescent organisms, a fruitful area for future studies given the frequent use and misuse of alcohol by human adolescents.

Altered ambient temperature and ethanol-induced conditioned place preference in mice

Previous studies with rats exposed to altered ambient temperature (Ta) or with mice selectively bred for their thermal response to ethanol have shown that a reduced hypothermic response is correlated with decreased place aversion and greater place preference, respectively. The present experiment was designed to test whether alterations in Ta would alter ethanol's ability to produce conditioned place preference in genetically heterogeneous mice. Three groups of mice underwent a differential conditioning procedure that paired one distinctive floor texture with ethanol (2.25 g/kg, i.p.) and a different floor texture with saline. During conditioning, each group was exposed to a different Ta: cold (10 degrees C), normal (21 degrees C), or warm (34 degrees C). Each group was further divided and subgroups were tested for preference at either the conditioning temperature or a different temperature. Consistent with previous findings, mice conditioned and tested at normal Ta developed a conditioned preference for the ethanol-paired floor. In contrast, mice exposed to a warm or cold Ta during conditioning or testing failed to show place conditioning. Although exposure to either warm or cold Ta interfered with place conditioning, only the warm Ta had an effect on hypothermia. These findings suggest that altered Ta produced stimuli that may have interfered with the association between floor cues and ethanol during conditioning or interfered with expression of this association during testing.

Fine structure of hippocampal dendrites in the dentate fascia of LS/SS-mice after chronic ethanol treatment

1. The effect of ethanol and its withdrawal on the dendritic microtubules in the dentate fascia of male mice was studied in the ethanol-sensitive, long-sleep (LS) line and the ethanol-insensitive, short-sleep (SS) line. 2. Both mouse lines were treated with a liquid ethanol diet. Dendrites in the dentate molecular layer (DML) of the right hippocampus were examined. 3. They revealed marked changes in microtubule density as compared with the controls. While the microtubule density in LS mice was significantly reduced by 15% and 18% in the middle and distal third of the DML, respectively, in SS mice the reduction (by 12%) took place in the distal third only. During withdrawal a recovery of the microtubule density has been observed in both lines.

Dose-related growth deficits in LS but not SS mice prenatally exposed to alcohol

Genetically based alcohol sensitivity may influence the severity of alcohol-related birth defects. To examine this question, measures of growth and survival were examined in offspring of the alcohol sensitive Long-Sleep (LS) and alcohol-resistant Short-Sleep (SS) mouse lines following prenatal ethanol exposure. Pregnant LS and SS mice received an ethanol dose of either 6 or 8 g/kg/day from days 7 through 18 of pregnancy. Control groups received a maltose-dextran solution made isocaloric to the 8 g/kg/day dose. Ethanol and maltose-dextrin solutions were administered as split doses, 6 h apart, via gavage. Nonintubated lab chow control groups were also included for both mouse lines. Offspring were fostered at birth to lactating mice of an outbred stock. Pregnancy was longer for ethanol-treated LS dams compared to maltose-dextrin and lab chow LS control groups, whereas pregnancy length for ethanol-treated SS dams was similar to SS controls. Prenatal ethanol exposure resulted in dose-related growth deficits in LS but not in SS litters. Line differences in postnatal growth deficits in response to prenatal alcohol exposure suggest maternal or fetal alcohol sensitivity influence alcohol-related birth defects.

Temperature dependence of ethanol depression in mice: dose response

Manipulation of body temperature during intoxication significantly alters brain sensitivity to ethanol. The current study tested the generality of this effect within the hypnotic dose range. Drug naive, male C57BL/6J mice were injected with 3.2, 3.6, or 4.0 g/kg ethanol (20% w/v) and were exposed to 1 of 7 designated temperatures from 13 degrees to 34 degrees C to manipulate body temperature during intoxication. Rectal temperature at return of righting reflex (RORR) was significantly, positively correlated with loss of righting reflex (LORR) duration and significantly, negatively correlated with blood ethanol concentration (BEC) at RORR at all three doses. These results indicate that increasing body temperature during intoxication increased ethanol sensitivity in C57 mice at all three doses tested and demonstrate the generality of temperature dependence across hypnotic doses in these animals. Interestingly, the LORR duration was dose-dependent at each ambient temperature, but the degree of body temperature change and the BEC at RORR were not dose-dependent. Overall, these results emphasize the importance of body temperature as a variable in ethanol research.

Effect of pentobarbital and gaseous anesthetics on rats selectively bred for ethanol sensitivity

Rats have been genetically selected to have a differential hypnotic response to an acute injection of ethanol. These high alcohol sensitive (HAS) and low alcohol sensitive (LAS) rats were used to investigate commonalities of the mechanism of action of several gaseous anesthetics, pentobarbital and ethanol. Similar studies have been carried out extensively with mouse lines also differentially sensitive to ethanol (short- and long-sleep mice). Like the mice, the rats are also differentially sensitive to the two gaseous anesthetics, enflurane and isoflurane. However, in contrast to results with these mice, we find that the HAS and LAS rats are differentially sensitive to halothane and pentobarbital in the same direction as their sensitivity to ethanol. In other studies, the rats also have been found to be differentially sensitive to phenobarbital as are SS and LS mice. These results show that, by the use of these anesthetics in combination with selectively bred rodent lines, many new opportunities for dissecting the molecular mechanisms of anesthetic agents present themselves.

Selective breeding for initial sensitivity to ethanol

Selective breeding for initial sensitivity to ethanol has been carried out by a number of investigators in order to investigate the mechanisms by which ethanol brings about a myriad of effects on the mammalian central nervous system. In addition the availability of these selectively bred animals provides clues to the causes of the genetic predisposition of humans to alcoholism. Eventually it is envisioned that the synteny between the mouse and human genomes will allow identification of specific genes responsible for acute effects of ethanol in both species as well as clues as to how alcoholism in humans can be better identified, prevented, and treated.

Influence of thyrotropin-releasing hormone and catecholaminergic interactions on CNS ethanol sensitivity

The role of catecholamine neuronal systems in mediating the analeptic and thermogenic effects of thyrotropin-releasing hormone (TRH) was examined in long-sleep (LS) and short-sleep (SS) mice. TRH [0.1 to 40 micrograms, intracerebroventricularly (icv)] was associated with a reduction in the sleep times of LS mice, but no dose of TRH had any effect on sleep times of SS mice. However, TRH (20 micrograms, icv) produced a 1.0 degree to 1.5 degrees C attenuation of the ethanol-induced hypothermia in both LS and SS mice. TRH did not change the rate of ethanol elimination in either line of mice, suggesting that the reduction in LS sleep times and attenuation of LS and SS hypothermia were due to decreased CNS ethanol sensitivity rather than an increase in the rate of ethanol metabolism. TRH (20 micrograms, icv) given alone produced an activation of central and peripheral catecholamine systems in LS, but not SS mice, as reflected by an increase in the in vivo tyrosine hydroxylase (TH) activity in the brain and adrenal gland. TRH, given with ethanol, prevented or attenuated ethanol-induced decreases in the brain and adrenal gland in vivo TH activity in LS mice but not SS mice. Thus, there was an association between the ability of TRH to produce an activation of catecholamine neuronal systems (increased rate of catecholamine biosynthesis) and the analeptic action of TRH to reduce the CNS depressant effects of ethanol (decreased sleep times).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of exercise on ethanol-induced hypothermia and loss of righting response in C57BL/6J mice

C57BL/6J mice were given 5 weeks of voluntary wheel running and then studied for ethanol (EtOH) sensitivity as indicated by EtOH-induced hypothermia and loss of righting response (LORR) after 3.8 g/kg EtOH (20% w/v). Mice were assigned to wheel (free access to a running wheel in the home cage) or no wheel conditions, and wheel counts were monitored by a computer at 5-min intervals around the clock. In Experiment 1, duration of EtOH-induced LORR was assessed as amount of time required for the animal to right itself three times in a 30-s period, and body temperature was assessed by rectal probe. Wheel animals showed significantly shorter LORR and significantly less hypothermia at regaining the righting response than no wheel controls. In Experiment 2, temperature was assessed at 45 and 90 min after EtOH challenge. Baseline temperatures for wheel and no wheel animals did not differ, but wheel animals showed dramatic resistance to EtOH-induced hypothermia at both time points. Together with our earlier work, these results provide evidence that prior exercise can offset the effects of EtOH intoxication in several domains of EtOH sensitivity.

A recombinant inbred strain analysis of sleep-time responses to several sedative-hypnotics

The results of previous studies suggested that the sleep-time differential between long-sleep (LS) and short-sleep (SS) mice decreases for a series of sedative-hypnotic drugs as lipid solubility increases. Using the LS x SS recombinant inbred (RI) strains, we have tested whether this relationship arises because of common genetic influences on the sleep-time responses or was simply a fortuitous difference between LS and SS mice. Mice were sleep-time tested after intraperitoneal injections of a variety of sedative-hypnotic drugs that vary in lipid solubility including alcohols, barbiturates, chloral hydrate, and urethane. Sleep-time values from each of these drugs were compared with ethanol-induced sleep times in the LS x SS RI strains. Significant genetic correlations were observed between ethanol-induced sleep time and those responses elicited by butanol, propanol, and chloral hydrate, but not by pentobarbital or secobarbital. When the partition coefficient (log P) values were compared with the genetic correlations, a significant relationship (r = -0.85) was observed. These data suggest that common genes mediate sedative-hypnotic reactions to ethanol and some drugs resembling it in log P value, and that anesthetic agents with low lipid solubility may be working through different mechanisms than drugs with greater lipid solubilities.

Selective breeding of rats differing in sensitivity to the effects of acute ethanol administration

Selective breeding of rats for sensitivity to the anesthetic effects of ethanol is being carried out with rats derived from the genetically heterogeneous N/Nih stock. Thirteen generations of within family selection have been achieved with replicate high (HAS), low (LAS) and control alcohol sensitive (CAS) lines. Significant separation between lines on sleep time and blood ethanol concentration (BEC) at awakening following ethanol administration has been achieved. In general, the results obtained so far replicate the findings with short (SS) and long (LS) sleep mice. One exception is that the high alcohol sensitivity rats (HAS) also appear more sensitive to pentobarbital relative to LAS rats. This finding is opposite to that which occurs with SS and LS mice where the low ethanol sensitive SS mice appear more sensitive to pentobarbital than the LS mice.

The relationship between brain temperature during intoxication and ethanol sensitivity in LS and SS mice

The present study characterized the relationship between brain temperature, rectal temperature, and ethanol sensitivity in the selectivity bred long-sleep (LS) and short-sleep (SS) mice. Radiotelemetric brain probe implanted and nonimplanted LS/lbg and SS/lbg male mice were injected with 2.5 and 4.9 g/kg ethanol, respectively, before exposure to ambient temperatures of 15 degrees C, 22 degrees C, or 34 degrees C. Ambient temperature significantly affected rectal temperature, brain temperature, and ethanol sensitivity, measured by impairment of righting reflex. Brain and rectal temperatures at return of righting reflex (RORR) were highly correlated. In SS mice brain and rectal temperatures at RORR were significantly positively correlated with loss of righting reflex (LORR) duration and significantly negatively correlated with blood ethanol concentration (BEC) at RORR. In LS mice rectal temperature at RORR was significantly negatively correlated with LORR duration, while both brain and rectal temperature at RORR were significantly positively correlated with BEC at RORR. The strength of the correlations and r2 values generated from linear regression analysis indicates that body temperature during intoxication can explain up to 52% of the variability in ethanol sensitivity in SS mice, but only 19% of the variability in ethanol sensitivity in LS mice. The correlational analyses are consistent with previous results based on comparisons between rectal temperature and ethanol sensitivity and extend to direct brain temperature measurement the evidence that decreasing temperature during intoxication decreases ethanol sensitivity in SS mice and increases ethanol sensitivity in LS mice.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Purinergic modulation of ethanol-induced sleep time in long-sleep and short-sleep mice

The long-sleep (LS) and short-sleep (SS) mice were selectively bred for differences in sensitivity to the depressant effects of ethanol. In addition to their differential sensitivity to ethanol, they are also differentially sensitive to purinergic agonists and antagonists. This suggests that there may be differences in the purinergic systems of these lines of mice which may aid in understanding how they differ in ethanol sensitivity. We have investigated whether these drugs are capable of modifying acute ethanol sensitivity as measured by ethanol-induced loss of the righting response (ethanol sleep time), waking blood and brain ethanol concentrations, and blood ethanol elimination rate. The purinergic agonists cyclohexyladenosine (CHA), L-phenylisopropyladenosine (PIA), 2-chloroadenosine (CAD), and N-ethylcarboxamidoadenosine (NEC) increased sleep time in both LS and SS mice, however, LS mice were generally more affected than SS. The LS and SS mice were also differentially sensitive to the purinergic antagonists, theophylline and caffeine. Blood and brain ethanol concentration on awakening suggested that CNS sensitivity to acute ethanol administration was altered by pretreatment with agonists but not antagonists. Two agonists, CHA and NEC, significantly lowered ethanol elimination in both lines of mice while PIA, CAD, and the antagonists theophylline, and caffeine were without affect on elimination rate. These data support previous observations that adenosine-mediated systems may be involved in the modulation of ethanol sensitivity.

Thermoregulation at a high ambient temperature following the oral administration of ethanol in the rat

This study was designed to assess the thermoregulatory mechanisms responsible for the elevation in body temperature following ethanol administration when exposed to a high ambient temperature (Ta). Male rats of the Fischer 344 strain were gavaged with 20% ethanol at doses of 0, 2.0, 4.0, 6.0, or 8.0 g/kg and were then placed in an environmental chamber set at a Ta of 37 degrees C. Metabolic rate normalized to body mass0.75 (MR), evaporative water loss (EWL), and motor activity were recorded for 60 min. Ethanol elicited a significant increase in colonic temperature and decrease in MR, EWL, and motor activity. Ethanol also significantly reduced the quantity of evaporated water per milliliter of oxygen consumed (E/M). Multiple linear regression analysis indicated that the two major factors which were associated with the ethanol-induced elevation in body temperature were an increase in MR and a decrease in E/M. Visual observation of behavior indicated that the normal grooming of saliva onto the fur during heat stress was impaired in ethanol-treated animals. Thus, during exposure to a high Ta, the acute ethanol-induced elevation in body temperature appears to be attributed to a suppression in both autonomic and behavioral mechanisms of heat dissipation.

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.

Isolate housing alters ethanol sensitivity in long-sleep and short-sleep mice

Beginning at 45 days of age, male long-sleep (LS) and short-sleep (SS) mice were placed into individual cages for 21-22 days. Control animals were group-housed for the same amount of time. At 65-66 days of age, animals were given anesthetic doses of ethanol, IP. Measures taken were sleep time, body temperature at 30 and 60 minutes postinjection and blood ethanol content (BEC) at regain of righting response. Compared to the same measures in group-housed animals, sleep times and hypothermia were attenuated in isolate-housed LS and SS mice. Isolate housing resulted in a 15% increase, compared to levels observed in group-housed animals, in BEC at regain of righting in LS; there was no significant difference in BEC in SS mice. The results indicated an isolation-related decrease in sensitivity to the anesthetic effects of ethanol in LS; the effect of isolation in SS may be an increased clearance rate of ethanol.

Responses to ethanol challenge in long- and short-sleep mice prenatally exposed to alcohol

Individual sensitivity to alcohol may influence the severity of functional deficits due to prenatal alcohol exposure. To examine this hypothesis, Long-Sleep (LS) and Short-Sleep (SS) mice, selectively bred for differences in ethanol-induced narcosis, were intubated with either 2.9 g/kg ethanol (E) or an isocaloric amount of sucrose (S) twice per day on days 7 through 15 of pregnancy. An untreated control group (C) was maintained for each line. Offspring were fostered to lactating Rockland-Swiss mice at birth. Males and females from each litter were challenged with an acute dose of ethanol (3.8 g/kg) at 30 days of age. Measures of sleep time duration, waking blood ethanol concentrations (BEC), rectal temperatures, heart rate, and ethanol clearance were obtained to examine whether the acute effects of ethanol are altered by prenatal alcohol exposure. Prenatal alcohol exposure did not differentially affect responses to ethanol challenge within either genotype. Ethanol-induced hypothermia, heart-rate depression, and sleep time did differ between genotypes, with LS more affected than SS mice. Ethanol clearance rates were faster for SS than LS mice. These results suggest postnatal pharmacological responses to acute ethanol challenge are not altered by prenatal alcohol exposure in LS and SS mice. Prenatal alcohol-exposed offspring of both mouse genotypes showed lower average heart rate responses than controls, suggesting this measure may be a sensitive indicator of prenatal alcohol effects in mice.

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.

Alcohol absorption rate affects hypothermic response in mice: evidence for rapid tolerance

Three studies were conducted to examine how absorption rate affects rapid tolerance to ethanol-induced hypothermia. Two procedures for administering alcohol were used to vary the rates of ethanol absorption: a 40-min intravenous (IV) infusion and the more rapidly absorbed intraperitoneal (IP) injection. Hypothermic responses of Long-Sleep (LS), Short-Sleep (SS), and DBA/2JIbg (DBA) mice were examined. Although IV ethanol infusions produced similar or higher blood ethanol levels (BELs) compared to IP administration, the degree of hypothermia was significantly greater with the more rapidly absorbed IP administration. It was concluded that the rate at which ethanol increases in the blood influences the degree of hypothermia: the greater the rate of blood ethanol increase, the greater the hypothermic effect. Rapid development of tolerance to ethanol may explain why a slow increase in BEL produces less hypothermia than a rapid increase in BEL. The IV route provides a precise method of drug administration for the study of acute tolerance.

LS X SS recombinant inbred strains of mice: initial characterization

In order to assess the genetic correlates of differences in ethanol-induced anesthesia, a set of 27 recombinant inbred (RI) strains was derived from an initial cross of the "long-sleep" (LS) and "short-sleep" (SS) selected lines of mice. In generations F24 and F25, samples of 534 and 580 mice from the LSXSS RI strains were tested for fall time, sleep time, and blood ethanol at awakening subsequent to intraperitoneal injection of a 4.1-g/kg body weight dose of ethanol. Approximately 2 weeks later, mice from F24 were also tested for body temperature lowering and blood-ethanol elimination rate (beta 60). Differences among the average ethanol-induced sleep-time scores of the RI strains are large (ranging from 36 to 171 min) and account for over 50% of the observed variance. Effects due to generation, sex, litters within strains, and the interaction between strain and generation are also significant, but account for relatively small proportions of the total variance. Quantitative genetic analyses of these data suggest that differences in sleep-time scores are polygenic; however, allelic differences at the albino (c) locus may have a pleiotropic effect. Genetic correlations between sleep time and blood ethanol at awakening (-0.79) and between body temperature 60 min after injection and beta 60 (+0.48) are significant. Because differences among the LSXSS RI strains are large and highly reliable, they should be valuable animal models for testing more searching hypotheses about the etiology of individual differences in ethanol-induced anesthesia.

Ethanol elimination in the anesthetized dog: intragastric versus intravenous administration

We computed by linear kinetics predicted equilibrated plasma concentrations, elimination parameters and availability of ethanol for fasting anesthetized dogs who received the same dose (11 mmol/kg) of ethanol twice, once intragastrically and once intravenously. Agreement between predicted (y) and observed (x) equilibrated plasma levels above 3 mmol/l was for intragastric ethanol y = 0.031 + 1.008x (r = 0.973) and for intravenous ethanol y = 0.2 + 0.99x (r = 0.992). Linear elimination (elimination rate, clearance, time of disappearance of half the dose) was significantly slower and Widmark's ratio r was significantly greater for intragastric than for intravenous ethanol. Apparent availability of intragastric ethanol, computed by dividing the intragastric by the intravenous plasma ethanol concentration at zero time (both values extrapolated from the linear portion of the blood alcohol curve), was 0.739 +/- 0.125. Considerable ethanol residuals were present in the stomach four hours after intragastric instillation. We conclude that retention of ethanol in the stomach, probably because of anesthesia, created the apparent differences in elimination of ethanol between intragastric and intravenous administration. Despite gastric retention, decrease of ethanol levels was linear above 3 mmol/l after intragastric instillation.

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.