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.     

Genetic basis of murine antibacterial defense to streptococcal lung infection

To evaluate the effect of genetic background on antibacterial defense to streptococcal infection, eight genetically diverse strains of mice (A/J, DBA/2J, CAST/Ei, FVB/NJ, BALB/cJ, C57BL/6J, 129/SvImJ, and C3H/HeJ) and tlr2-deficient mice (C57BL/6^tlr2−/−) were infected with three doses of Streptococcus zooepidemicus (500, 5,000, or 50,000 colony-forming units) by alveolar challenge. There was a range of susceptibility between the strains at each dose and time point (6, 24, and 96 h). At the lowest dose, the 129/SvImJ and C3H/HeJ strains had significantly higher bacterial counts at all time points after infection, when compared to A/J, DBA/2J, CAST/Ei, FVB/NJ, which were resistant to infection at the low dose of innoculum. At the medium dose, 129/SvImJ and C3H/HeJ had higher bacterial counts, while A/J, DBA/2J, and BALB/cJ showed reduced streptococcal growth. After the highest dose of Streptococcus, there were minimal differences between strains, suggesting the protective impact of modifier genes can be overcome. TLR2-deficient animals contained increased bacterial load with reduced cytokines after 96 h when compared to C57BL/6J controls suggesting a role of innate immunity in late antibacterial defense. Overall, we identify vulnerable (129/SvlmJ and C3H/HeJ) and resistant (A/J, FVB, and DBA) mouse strains to streptococcal lung infection, which demonstrate divergent genetic expression profiles. These results demonstrate that innate differences in pulmonary host defense to S. zooepidemicus are dependent on host genetic factors.     

Comparison of lipids in total brain tissue from five mouse genotypes.

Brain tissue from adult male and female mice of the C57BL/6J, C57BL/6J-AW-J, BALB/cJ, SJL/J, and DBA/2J genotypes was examined for brain weight, total protein, total lipid, cholesterol, phospholipid, plasmalogen, sulfatide, nonganglioside-glycolipid sphingosine, and ganglioside N-acetyl neuraminic acid, fatty acid, and sphingosine. No significant differences were found between sexes for any of these constituents. When compared to the overall average obtained for other animals, the DBA/2J, C57BL/6J-AW-J, and BALB/cJ mice contained lower quantities of plasmalogen and sulfatide compared to the overall averages obtained for the other genotypes. In addition, the sterol content in DBA/2J mice was significantly higher than the overall average value obtained for the other animals.     

Genetic differences in nicotine-induced conditioned taste aversion

Genetic differences in nicotine-induced conditioned taste aversion were examined using inbred mice. Adult male C57BL/6J, DBA/2J, BALB/cJ and C3H/heJ mice were adapted to a 2-h per day water access regimen. Subsequently, mice received nicotine injections (0.5, 1.0 or 2.0 mg/kg) immediately after 1-h access to a NaCl flavored solution. DBA and C3H mice developed dosedependent aversions to the nicotine-paired flavor. BALB mice showed only minor reductions in intake with no difference between the nicotine dose groups. C57BL mice did not show development of nicotine-induced conditioned taste aversion. These results demonstrate that nicotine's aversive motivational effect is strongly influenced by genotype. Further, genetic sensitivity (DBA mice) or insensitivity (C57BL mice) to nicotine-induced conditioned taste aversion was similar to reports of genetic sensitivity to ethanol's aversive effect measured in this design.     

Tyrosine hydroxylase in various brain regions of three strains of mice differing in spontaneous activity, learning ability, and emotionality.

Tyrosine hydroxylase has been measured in brains of three inbred strains of mice ; DBA/2J ; C57 BL/6J and BALB/cJ. Compared to C57 BL/6J, DBA/2J showed a higher enzyme activity in hypothalamus, a lower activity in pons-medulla, and no significant changes in cortex or striatum. BALB/cJ showed a higher level of activity in all regions studied (striatum, pons-medulla and hypothalamus). No effect of isolation or of social dominance position were noted on the enzyme activities in C57 BL/6J or BALB/cJ mice.     

Restraint increases prolactin and REM sleep in C57BL/6J mice but not in BALB/cJ mice

Sleep is generally considered to be a recovery from prior wakefulness. The architecture of sleep not only depends on the duration of wakefulness but also on its quality in terms of specific experiences. In the present experiment, we studied the effects of restraint stress on sleep architecture and sleep electroencephalography (EEG) in different strains of mice (C57BL/6J and BALB/cJ). One objective was to determine if the rapid eye movement (REM) sleep-promoting effects of restraint stress previously reported for rats would also occur in mice. In addition, we examined whether the effects of restraint stress on sleep are different from effects of social defeat stress, which was found to have a non-REM (NREM) sleep-promoting effect. We further measured corticosterone and prolactin levels as possible mediators of restraint stress-induced changes in sleep. Adult male C57BL/6J and BALB/cJ mice were subjected to 1 h of restraint stress in the middle of the light phase. To control for possible effects of sleep loss per se, the animals were also kept awake for 1 h by gentle handling. Restraint stress resulted in a mild increase in NREM sleep compared with baseline, but, overall, this effect was not significantly different from sleep deprivation by gentle handling. In contrast, restraint stress caused a significant increase in REM sleep compared with handling in the C57BL/6J mice but not in BALB/cJ mice. Corticosterone levels were significantly and similarly elevated after restraint in both strains, but prolactin was increased only in the C57BL/6J mice. In conclusion, this study shows that the restraint stress-induced increase in REM sleep in mice is strongly strain dependent. The concomitant increases in prolactin and REM sleep in the C57BL/6J mice, but not in BALB/cJ mice, suggest prolactin may be involved in the mechanism underlying restraint stress-induced REM sleep. Furthermore, this study confirms that different stressors differentially affect NREM and REM sleep. Whereas restraint stress promotes REM sleep in C57BL/6J mice, we previously found that in the same strain, social defeat stress promotes NREM sleep. As such, studying the consequences of specific stressful stimuli may be an important tool to unravel both the mechanism and function of different sleep stages.     

Visual detection, pattern discrimination and visual acuity in 14 strains of mice

Based on the procedure of Prusky et al. (2000, Vision Research, 40, 2201-2209), we used a computer-based, two-alternative swim task to evaluate visual detection, pattern discrimination and visual acuity in 14 strains of mice from priority groups A and B of the JAX phenome project (129S1/SvImJ, A/J, AKR/J, BALB/cByJ, BALB/cJ, C3H/HeJ, C57BL/6J, CAST/Ei, DBA/2J, FVB/NJ, MOLF/Ei, SJL/J, SM/J and SPRET/Ei). Each mouse was tested for eight trials/day for 8 days on each of the three tests. There was a significant strain difference in visual ability in all three tests. Mice with reported normal vision (129S1/SvImJ, C57BL/6J and DBA/2J) and one albino strain (AKR/J) performed very well in these tasks. The other albino strains (A/J, BALB/cByJ and BALB/cJ) took longer to learn the tasks than mice with normal vision and did not reach the criterion of 70% correct. Mice with retinal degeneration (C3H/HeJ, FVB/NJ, MOLF/Ei and SJL/J) performed only at chance levels as did the three strains with unknown visual abilities (CAST/Ei, SM/J and SPRET/Ei). Because many behavioral tasks for rodents rely on visual cues, we suggest that the visual abilities of mice should be evaluated before they are tested in commonly used visuo-spatial learning and memory tasks.     

Alcohol withdrawal reactions and reserpine effects in inbred strains of mice

Mice of different inbred strains were treated with ethanol for 3 days, by inhalation of alcohol vapor and daily injections of pyrazole. Within strains, “alcohol-adapted” mice were compared with controls. The alcohol-adapted mice received 3.8% (w/v) alcohol in their drinking water for one week and 7.5% alcohol for the next 16 or 19 weeks. During the inhalation period, C57BL mice had lower blood alcohol levels than DBA mice, and alcohol-adapted mice had slightly lower blood levels than controls. On withdrawal the mice were examined repeatedly for convulsions elicited by handling, a measure of the intensity of withdrawal reactions. The withdrawal scores of C57BL mice were significantly lower than those of DBA, BALB or Swiss-Webster mice, more so than could be accounted for by the difference in blood alcohol levels. Mice of 3 strains were treated with reserpine and observed for behavioral effects, including convulsions on handling. Strain differences in reserpine effects closely paralleled the strain differences in alcohol withdrawal seizures.     

Comparison of lipids in total brain tissue from five mouse genotypes

Brain tissue from adult male and female mice of the C57BL/6J, C57BL/6J-A^w—J, BALB/cJ, SJL/J, and DBA/2J genotypes was examined for brain weight, total protein, total lipid, cholesterol, phospholipid, plasmalogen, sulfatide, nonganglioside—glycolipid sphingosine, and ganglioside N-acetyl neuraminic acid, fatty acid, and sphingosine. No significant differences were found between sexes for any of these constituents. When compared to the overall average obtained for other animals, the DBA/2J, C57BL/6J-A^w−J, and BALB/cJ mice contained lower quantities of nonganglioside—glycolipid sphingosine. The DBA/2J and C57BL/6J-A^w−J mice also contained lower quantities of plasmalogen and sulfatide compared to the overall averages obtained for the other genotypes. In addition, the sterol content in DBA/2J mice was significantly higher than the overall average value obtained for the other animals.     

Genetic differences in ethanol-induced hyperglycemia and conditioned taste aversion.

Genetic differences in the hyperglycemic response to acute ethanol exposure and ethanol-induced conditioned taste aversion were examined using inbred mice. Adult male C57BL/6J and DBA/2J mice were injected with ethanol (0-6 g/kg, I.P.) and blood glucose levels determined over 4 h. C57 mice demonstrated greater dose-dependent elevations in blood glucose compared to DBA mice. In a conditioned taste aversion procedure, water deprived mice received ethanol injections (1-4 g/kg, I.P.) immediately after access to a NaCl flavored solution. DBA mice developed aversion to the ethanol-paired flavor at a lower dose (2 g/kg) than C57 mice. These results provide further support for a possible inverse genetic relationship between sensitivity to ethanol-induced hyperglycemia and sensitivity to conditioned taste aversion.     

Sex and strain differences in the hepatotoxic response to acute cocaine administration in the mouse

Cocaine-induced hepatotoxicity was examined in vivo in a dose-responsive manner in C57BL/6Ibg, DBA/2Ibg, C3H/2Ibg, and Balb/cJ mice. Serum glutamic-pyruvic transaminase (SGPT) activities were determined 24 hours after intraperitoneal (IP) administration of cocaine (20 to 100 mg/kg). Significant elevations (100- to 150-fold) in SGPT were observed in male mice receiving cocaine. Significant differences in sensitivity to cocaine-induced hepatotoxicity were found among males of the inbred strains, with Balb being most sensitive and C57BL being least sensitive and C3H and DBA strains exhibiting intermediate sensitivity. Female mice of the four inbred strains were more resistant than males to cocainemediated hepatotoxicity, as indicated by only twofold to tenfold elevations in SGPT values. Among the females, sensitivity of the four inbred strains—as indicated by dose response curves—fell into two categories: the sensitive strains (C3H and C57BL) and the resistant strains (Balb and DBA). Pretreatment of males of the four inbred strains with the P-450 inducer phenobarbital resulted in enhancement of cocaine-mediated hepatotoxicity in the C57BL and Balb but not the C3H and DBA mice. Phenobarbital pretreatment of females of the four inbred strains resulted in enhancement of the hepatotoxic response to cocaine in the C3H, DBA, and Balb mice. Phenobarbital-pretreated C57BL females exhibited a 100% mortality rate after the acute cocaine dose, and thus no determination of hepatotoxicity could be established for them. These data demonstrate sex and strain differences in cocaine-induced hepatotoxicity and suggest that phenobarbital pretreatment does not uniformly enhance the hepatotoxicity of cocaine.     

A relationship between synaptosomal GABA uptake and blood pressure in five inbred strains of mice

Synaptosomal GABA uptake, sodium-dependent GABA binding to synaptic membranes and GABA receptor binding were measured in the cerebral cortex of five inbred strains of mice. These were the SWR/J, BALB/cJ, DBA/1J, C57BL/10J and C3HeB/FeJ strains. A highly significant negative correlation was found to exist between GABA uptake and blood pressure (r = ?0.92). A similarly good negative correlation occurred between sodium-dependent GABA binding and blood pressure. A poor correlation was observed between blood pressure and GABA receptor binding (r = ?0.46). Taken together with other evidence that exists in the literature, these results suggest that in mice blood pressure could be under the influence of the GABA system.     

Streptobacillus moniliformis epizootic in barrier-maintained C57BL/6J mice and susceptibility to infection of different strains of mice

We report a Streptobacillus moniliformis epizootic in barrier-maintained SPF mice. Although various inbred and F1 hybrid strains of mice have been kept in this animal facility, only C57BL/6J Han [corrected] mice showed clinical signs of disease. During the course of the epizootic, 825 breeding animals (approximately 36% of the breeders) died or had to be killed because of severe clinical signs. Although sequential treatment with ampicillin and chlortetracycline gave good therapeutic results, the animal facility was vacated in order to exclude any risk of cross-contamination of the other rodent colonies in our institute. The source and route of transmission of S. moniliformis could not be elucidated. To investigate strain dependent differences experimental infection of different strains of mice with our S. moniliformis isolate was performed. After oral infection only C57BL/6J showed the typical signs of a cervical lymphadenitis and gave an immunological response. BALB/cJ, C3H/He, DBA/2J, CB6F1 and B6D2F1 mice were not affected except in two cases of DBA/2J and B6D2F1 mice where seroconversion was observed. After intravenous infection of C57BL/6J, DBA/2J [corrected] and BALB/cJ all animals showed positive titers in the indirect immunofluorescence test (IIF). One hundred percent of the C57BL/6J, forty percent of the DBA/2J, and none of the BALB/cJ mice developed severe symptoms. The results demonstrate that the susceptibility to streptobacillosis is predominantly influenced by genetic factors.     

Genetic Determination of the Developmental Program for Mouse Liver β-GALACTOSIDASE: Involvement of Sites Proximate to and Distant from the Structural Gene

The identification and mode of action of genetic loci that program gene expression during development are important for understanding differentiation in higher organisms. Previous work from this laboratory has identified two patterns for the postnatal development of liver beta-galactosidase among inbred mouse strains: type I, where activity levels remain constant after about 30 days of age, is found in strains DBA/2J, CBA/J, and BALB/cJ, among others; type II, where activity levels increase between 25 and 50 days of age to reach a new adult level, is found in strain C57BL/6J and related strains. It has been shown that the type I vs. type II developmental difference between strains C57BL/6J and DBA/2J is due to variation at a locus, Bgl-t, that maps with the beta-galactosidase complex, [Bgl], on chromosome 9. In the present study, we have confirmed the existence of Bgl-t as a temporal locus within [Bgl] by analysis of both a congenic strain carrying the beta-galactosidase complex of strain CBA/J in the C57BL/6J genetic background and a cross of strains CBA/J and C57BL/6J. The existence of additional temporal loci for beta-galactosidase that segregate independently of the structural gene and participate in determination of the type I vs. type II difference was revealed by analysis of: (1) a congenic strain containing the beta-galactosidase complex of strain BALB/cJ in the C57BL/10Sn background; (2) recombinant inbred lines derived from progenitor strains C57BL/6ByJ and BALB/cByJ; and (3) a genetic cross between strains C57BL/6ByJ and BALB/cByJ. Thus, for these pairs of strains, the type I vs. type II developmental difference is due to variation at a temporal locus (or loci) unlinked to the enzyme structural gene, and not at Bgl-t. These facts, together with information gathered from an examination of the distribution of beta-galactosidase phenotypes among over 100 inbred strains (Breen, Lusis and Paigen 1977), have led us to conclude that the postnatal developmental pattern for liver beta-galactosidase is determined by a set of interacting temporal genes. One of these, Bgl-t, is located within [Bgl], and one or more are separable from [Bgl] by recombination. A possible mode of interaction among the temporal and instructural loci is suggested.     

Cannabinoid-serotonin interactions in alcohol-preferring vs. alcohol-avoiding mice

Because cannabinoid and serotonin (5-HT) systems have been proposed to play an important role in drug craving, we investigated whether cannabinoid 1 (CB1) and 5-HT(1A) receptor ligands could affect voluntary alcohol intake in two mouse strains, C57BL/6 J and DBA/2 J, with marked differences in native alcohol preference. When offered progressively (3-10% ethanol) in drinking water, in a free-choice procedure, alcohol intake was markedly lower (approximately 70%) in DBA/2 J than in C57BL/6 J mice. In DBA/2 J mice, chronic treatment with the cannabinoid receptor agonist WIN 55,212-2 increased alcohol intake. WIN 55,212-2 effect was prevented by concomitant, chronic CB1 receptor blockade by rimonabant or chronic 5-HT(1A) receptor stimulation by 8-hydroxy-2-(di-n-propylamino)-tetralin, which, on their own, did not affect alcohol intake. In C57BL/6 J mice, chronic treatment with WIN 55,212-2 had no effect but chronic CB1 receptor blockade or chronic 5-HT(1A) receptor stimulation significantly decreased alcohol intake. Parallel autoradiographic investigations showed that chronic treatment with WIN 55,212-2 significantly decreased 5-HT(1A)-mediated [35S]guanosine triphosphate-gamma-S binding in the hippocampus of both mouse strains. Conversely, chronic rimonabant increased this binding in C57BL/6 J mice. These results show that cannabinoid neurotransmission can exert a permissive control on alcohol intake, possibly through CB1-5-HT(1A) interactions. However, the differences between C57BL/6 J and DBA/2 J mice indicate that such modulations of alcohol intake are under genetic control.     

Effects of repeated maternal separation on prepulse inhibition of startle across inbred mouse strains

A growing body of research implicates genetic factors and childhood trauma in the etiology of neuropsychiatric diseases such as schizophrenia. However, there remains little understanding of how genetic variation influences early life stress to affect later disease susceptibility. Studies in rats have shown that postnatal maternal separation (MS) results in later deficits in prepulse inhibition of the acoustic startle response (PPI), an impairment in sensorimotor gating found in schizophrenic patients. In the present study, genetic differences in the effects of repeated MS on PPI were examined in eight inbred strains of mice (129S1/SvImJ, 129P3/J, A/J, BALB/cJ, BALB/cByJ C57BL/6J, DBA/2J and FVB/NJ). Mice were assigned to either MS (180 min/day on postnatal days P0-P13), 'handling' (15 min/day, P0-P13) or facility-reared conditions and tested for PPI at 12 weeks of age. Results demonstrated major strain differences in the production of viable offspring irrespective of MS, leading to the exclusion of 129P3/J, A/J and BALB/cJ from the study. Pups from the five remaining strains exhibited marked differences in the acoustic startle response and PPI, confirming previous strain comparisons. However, MS produced no significant effects on PPI in any of the strains tested. A second form of postnatal stress (repeated footshock) also failed to alter PPI in the one strain studied, C57BL/6J. Present results demonstrate that the form of MS studied herein does not provide a robust model of early life stress effects on PPI in the mouse strains tested. The development and validation of a reliable mouse model of early life stress remains an important research goal.     

NaCl taste thresholds in 13 inbred mouse strains

Molecular mechanisms of salty taste in mammals are not completely understood. We use genetic approaches to study these mechanisms. Previously, we developed a high-throughput procedure to measure NaCl taste thresholds, which involves conditioning mice to avoid LiCl and then examining avoidance of NaCl solutions presented in 48-h 2-bottle preference tests. Using this procedure, we measured NaCl taste thresholds of mice from 13 genealogically divergent inbred stains: 129P3/J, A/J, BALB/cByJ, C3H/HeJ, C57BL/6ByJ, C57BL/6J, CBA/J, CE/J, DBA/2J, FVB/NJ, NZB/BlNJ, PWK/PhJ, and SJL/J. We found substantial strain variation in NaCl taste thresholds: mice from the A/J and 129P3/J strains had high thresholds (were less sensitive), whereas mice from the BALB/cByJ, C57BL/6J, C57BL/6ByJ, CE/J, DBA/2J, NZB/BINJ, and SJL/J had low thresholds (were more sensitive). NaCl taste thresholds measured in this study did not significantly correlate with NaCl preferences or amiloride sensitivity of chorda tympani nerve responses to NaCl determined in the same strains in other studies. To examine whether strain differences in NaCl taste thresholds could have been affected by variation in learning ability or sensitivity to toxic effects of LiCl, we used the same method to measure citric acid taste thresholds in 4 inbred strains with large differences in NaCl taste thresholds but similar acid sensitivity in preference tests (129P3/J, A/J, C57BL/6J, and DBA/2J). Citric acid taste thresholds were similar in these 4 strains. This suggests that our technique measures taste quality-specific thresholds that are likely to represent differences in peripheral taste responsiveness. The strain differences in NaCl taste sensitivity found in this study provide a basis for genetic analysis of this phenotype.     

Cadmium induced limb defects in mice: strain associated differences in sensitivity.

Cadmium (CdSO4) was given ip on day 9 at 12 or 24 mumol/kg to pregnant CD-1 (non-inbred) mice. Fetuses showed malformations of the limbs, face, trunk, and tail. There was a statistically significant relationship between the dose of cadmium and the malformation rate. Cadmium (12 mumol/kg ip on day 9) was then given to mice of six inbred strains three of which (A/J, BALB/cJ, and C57BL6J) carry a gene cdm for resistance to cadmium-induced testicular damage, and three strains (AKR/J, CBA/J, and DBA/2J) which do not. Paradoxically, the three strains resistant to cadmium induced testicular damage were significantly more sensitive to its teratogenic effects than were the other three strains. In all inbred strains most malformations involved the limbs. All forelimb defects found in inbred or non-inbred cadmium treated mice were postaxial and indistinguishable from those produced by acetazolamide in mice. The remarkable similarity of the cadmium- and acetazolamide-induced forelimb malformations may be a reflection of the limited number of ways that a rodent forelimb can react to a teratogenic insult. The hindlimb defects were all preaxial.     

GABA(A) receptor beta(2) subunit mRNA content is differentially regulated in ethanol-dependent DBA/2J and C57BL/6J mice

Chronic ethanol treatment is known to alter gene expression and function of γ-aminobutyric acid type-A (GABA_A) receptors. Here we focus on the β₂ subunit which is widely expressed in the mammalian brain, and plays a key role in the GABA binding site. Previous studies using rodent models of ethanol dependence show either increased or no change of β₂ subunit mRNA and peptide content following chronic ethanol administration. In humans, polymorphism at the β₂ subunit is associated with ethanol dependence in some, but not all, populations. In the present study we measured mRNA content in the cerebellum and cerebral cortex using ethanol-naive and ethanol-dependent DBA/2J and C57BL/6J mice. The DBA/2J strain displays severe ethanol withdrawal severity, while the C57BL/6J strain shows milder withdrawal reactions. RNase protection analysis demonstrated that the DBA/2J strain is more sensitive to ethanol-induced increases in β₂ subunit mRNA content in the cerebellum, showing significant increases at lower blood ethanol concentrations than C57BL/6J mice. The ethanol-induced regulation in C57BL/6J mice appears to be more complex, with decreases in β₂ subunit mRNA content at low blood ethanol concentrations, and increases at higher concentrations. These data suggest that differences between C57BL/6J and DBA/2J mice in the degree of physical dependence (withdrawal) on ethanol may be related to differential sensitivity to ethanol regulation of β₂ subunit expression.