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.     

Genotype modulates age‐related alterations in sensitivity to the aversive effects of ethanol: an eight inbred strain analysis of conditioned taste aversion

Adolescent individuals display altered behavioral sensitivity to ethanol, which may contribute to the increased ethanol consumption seen in this age‐group. However, genetics also exert considerable influence on both ethanol intake and sensitivity. Currently there is little research assessing the combined influence of developmental and genetic alcohol sensitivities. Sensitivity to the aversive effects of ethanol using a conditioned taste aversion (CTA) procedure was measured during both adolescence (P30) and adulthood (P75) in eight inbred mouse strains (C57BL/6J, DBA/2J, 129S1/SvImJ, A/J, BALB/cByJ, BTBR T⁺tf/J, C3H/HeJ and FVB/NJ). Adolescent and adult mice were water deprived, and subsequently provided with access to 0.9% (v/v) NaCl solution for 1 h. Immediately following access mice were administered ethanol (0, 1.5, 2.25 and 3 g/kg, ip). This procedure was repeated in 72 h intervals for a total of five CTA trials. Sensitivity to the aversive effects of ethanol was highly dependent upon both strain and age. Within an inbred strain, adolescent animals were consistently less sensitive to the aversive effects of ethanol than their adult counterparts. However, the dose of ethanol required to produce an aversion response differed as a function of both age and strain.     

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.     

Strain differences in amiloride inhibition of NaCl responses in mice,Mus musculus

Summary The effects of lingual treatment with amiloride, an inhibitor of salt taste responses in several mammalian species, on NaCl responses of the chorda tympani nerve were compared between four inbred strains of mouse (BALB/cCrSlc, DBA/2CrSlc, C57BL/6CrSlc and C3H/HeSlc). In C57BL and C3H mice amiloride significantly suppressed responses of the chorda tympani nerve to NaCl at a concentration 0.1 M or more whereas in BALB and DBA mice the drug did not significantly affect the responses to NaCl at any concentration, suggesting a lack of the amiloride-sensitive receptor component for NaCl in the latter two strains.A two-bottle preference test demonstrated that all strains of mouse usually showed no preference for NaCl at any concentration and avoided NaCl at 0.3 M or more, although some differences were observed in that C57BL and C3H mice showed aversive responses to 0.1 and 0.15 M NaCl, whereas BALB and DBA mice were indifferent to these solutions.The results suggest that there exist prominent differences between mouse strains in the amiloride-sensitive component of their salt receptor systems. However, in mice the taste information derived from the amiloride-sensitive receptor component probably has no remarkable effect on behavioral responses to NaCl except for a possible contribution to decreasing aversion thresholds for NaCl by increasing overall taste information about NaCl.     

Amiloride is an ineffective conditioned stimulus in taste aversion learning in C57BL/6J and DBA/2J mice

The epithelial sodium channel (ENaC) blocker amiloride has been shown to increase the behaviorally measured NaCl detection threshold in mice. In this study, a conditioned taste aversion (CTA) paradigm was used to examine whether 100 microM amiloride has a perceptible taste that could contribute to this observed decrease in behavioral responsiveness. Eighty-four C57BL/6J (B6) and 64 DBA/2J (D2) mice were divided into eight groups (n=8-12 per group), in which half received an injection of 0.15 M LiCl (2 mEq/kg) and the other half an equivalent saline injection, in three conditioning trials. The four conditioned stimuli were 100 microM amiloride hydrochloride, water, 0.1 and 0.3 M NaCl. Neither strain demonstrated acquisition of a CTA to amiloride in a brief-access (BA) taste test (5 s trials in the gustometer). Although 0.3 M NaCl is inherently aversive, its pairing with LiCl led to significantly further decreases in licking during the BA test on salt trials in both strains. The D2 strain clearly avoided 0.1 M NaCl, whereas avoidance of this stimulus was more equivocal in B6 mice. The inefficacy of amiloride to serve as a conditioned stimulus in taste aversion learning involving three LiCl pairings suggests that the effects of this ENaC blocker on taste-related behavioral responses to NaCl are likely due to its pharmacological interference with sodium taste transduction.     

Extinction of passive avoidance response in various mouse strains

Dependence of the passive avoidance extinction dynamics on a mouse strain was shown. Mice C57BL/6J and AKR/J extinguished more quickly relative to DBA/2J, CBA/Lac and BALB/c, and this extinction was stable. Individual instability of extinction was characteristic of C3H/HeJ mice. Extinction of the passive avoidance in mice CBA/Lac and BALB/c was slower: with a delay in the beginning and prolonged retention of memory trace of the shock exposure. In DBA/2J mice, the extinction was impaired. These data suggest that DBA/2J, CBA/Lac and BALB/c mice constitute groups of risk with high predisposition to impairment of extinction of memory of aversive events, which is thought to be a symptom of a depressive-like state.     

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.     

Genotype-dependent mice behavior in cognitive tasks. Effect of noopept

The interstrain differences in performance of C57BL/6J, BALB/c and DBA/2J male mice in two cognitive tasks were found. Mice C57BL/6J showed good learning ability and preservation of memory traces tested 10 days after performance in a simplified version of Morris water maze. Mice BALB/c learned the task but, virtually, no long-term memory traces were revealed, whereas DBA/2J demonstrated poor learning. The effect of nootropic drug Noopept (GVS-111, N-phenil-acetyl-L-prolylglycin ethyl ether) was shown to be genotype-dependent. Its administration (0.5 mg/kg i.p., 15 min before learning) improved the long-term memory in Morris test in BALB/c mice but failed to produce any improvement in C57BL/6J. The ability of mice for extrapolation of the direction of stimulus movement differently changed after Noopept injections: the proportion of correct task solutions increased in C57BL/6J and BALB/c mice, whereas the performance of DBA/2J did not change.     

Dimethylnitrosamine metabolism: II. In vitro activation of dimethylnitrosamine by hepatic and renal tissues from crosses among BALB/c, DBA and C57BL mice

Crosses among BALB/c, C57BL and DBA mice were performed to investigate the genetic mechanisms involved in metabolism of DMN by renal and hepatic tissues. Liver S-9 fractions from parental strain DBA had the greatest potential to activate DMN and liver fractions from parental strain BALB/c had the lowest. No age or sex-related differences were observed within strain. Crossing of either C57BL or DBA to BALB/c mice resulted in F1 hybrids with liver microsomal enzymes that gave results similar to the BALB/c parental strain. There were no sex or age differences within crossbred strains in the potential of liver to activate DMN. In contrast male DBA and C57BL parental mice renal S-9 fractions did not differ significantly from each other but did differ significantly from male BALB/c renal fractions and from female and immature animals of all strains. Crossing of either DBA or C57BL mice with BALB/c mice resulted in male F1 hybrids whose renal S-9 fractions did not differ significantly from males of the parental BALB/c strain. In all instances, male renal S-9 fractions had a significantly greater potential to activate DMN than female or immature animals. F1 DBA X C57BL hybrids had renal S-9 fractions that did not differ significantly from the parental strains. These data suggest that the gene(s) for low DMN metabolism of BALB/c mice are apparently dominant over the genes from both DBA and C57BL. The exact genetic or physiological mechanism needs further elucidation.     

Variations in the behaviors to novel objects among five inbred strains of mice

Novelty stimuli cause various behavioral responses, such as exploration and avoidance, and contextual variables may contribute to the behavioral outputs. Here, we tried to compare the behavioral responses to novel objects of five inbred strains of mice (C57BL/6J, 129/svJae, C3H/HeJ, BALB/cJ and DBA/2J) by using a modified novel object test where a small light-weight cube wrapped with paper was presented to mice in a home cage without beddings. In response to these objects, the C57BL/6J, 129/svJae and C3H/HeJ mice showed mild exploratory behaviors, such as approaching, sniffing or brief contact. In striking contrast, the BALB/cJ and DBA/2J mice, which have been known to show high avoidance/low exploration in other behavioral paradigms, exhibited play-like secondary reactions toward the objects after initial primary exploratory behaviors. Specifically, DBA/2J mice would move the object around in the cage, holding it with their mouths, and BALB/cJ mice would gnaw the object, eventually stripping off the wrapping paper. Such behaviors decreased when similar objects were presented repeatedly. The present results suggest that active manipulations of novel objects may be a relevant parameter for measuring novelty-induced behaviors in mice and appear to be strongly influenced by genetic factors.     

Nicotine consumption of several mouse strains using a two bottle choice paradigm

The two bottle choice paradigm provides a convenient method for the rapid screening of preferences of nicotine and a variety of other substances in rodents. A non-expensive, home-made bottle system with low fluid loss due to leakage or evaporation is introduced. Using this system, we tested nicotine preference of the mouse strains NMRI, C3H/J, DBA/2, ST/bJ, C57BL/6 and a cross between male A/J and female NMRI. Our results show different nicotine preference of tested mice with high nicotine preference of C57BL/6, a lower preference of C3H/J, A/J×NMRI, DBA/2 and NMRI and the lowest of ST/bJ.     

Behavior of mice from different strains: modifications produced by noopept

Genotype-dependent behavioral effects were demonstrated in BALB/c, C57BL/6J [Russian character: see text] DBA/2J mice after injections of nootropic drug Noopept. In an elevated plus maze, drug administration induced an increase in the number of enterings into bright arms in BALB/c mice, whereas the opposite effect was observed in C57BL/6J. After the Noopept administration, animals from all the three strains increased the number of active avoidance reactions in stress-inducing slip-funnel test. A significant intensification of exploration behavior was observed in a closed plus-maze in BALB/c and C57BL/6J. The Noopept affected weakly or had no effect on the behavior of DBA/2J mice.     

Background matters: the effects of estrogen receptor alpha gene disruption on male sexual behavior are modified by background strain

One approach to study interactions between behavior and genetics is to use inbred mice with different genetic backgrounds. To examine the effect of background on a specific gene, we conducted a series of experiments with a well-characterized knockout (KO) mouse, the estrogen receptor alpha KO (ERalphaKO). The ERalphaKO mouse has so far been examined in one inbred line, C57BL/6J. Here, we examined the behavior of ERalphaKO mice within three different backgrounds mixed with C57BL/6J; DBA/2J, BALB/c, and A/J. First, we assessed masculine sexual behavior in both intact male and testosterone-treated female offspring. More ERalphaKO males in the DBA/2J (5/12) and BALB/c (5/13) backcrosses displayed intromissions and many ejaculated as compared with males in a C57BL/6J and A/J mixed background. Many fewer ERalphaKO females than males displayed masculine sexual behavior in any of the three hybrid crosses. We assessed fertility in males from the C57BL/6J by DBA/2J cross and found that one of 12 ERalphaKO males sired a litter. Several other characteristics of sexual behavior and physiology were unaffected by genetic background in ERalphaKO mice. Our data suggest that genetic background has dramatic effects on male sexual behavior and its dependence on the ERalpha gene.     

Genetic differences in BCG-induced resistance to Schistosoma mansoni are not controlled by genes within the major histocompatibility complex of the mouse.

Induction of nonspecific resistance to Schistosoma mansoni infection after the i.v. injection of viable BCG was investigated in outbred mice and a panel of inbred and H-2 congenic strains. Significant protection was induced in CF1, A/J, C57BL/6, C57BL/10, DBA/2, C57BR, and SJL mice. BALB/c mice were not protected whereas CBA and C3H mice expressed intermediate degrees of protection. Expression of the protective phenomenon is not controlled by genes within the MHC as shown by the marked differences in response between BALB/c and DBA/2 (H-2d) as well as between C57BR and C3H (H-2k) mice. H-2 congenic strains with C57BL/10 background (B10.A and B10.D2) were high responders. BALB.B10 mice carrying the high responder (B10) MHC on the nonresponder (BALB/c) background were not protected. The degree of splenic hypertrophy did not correlate with the expression of nonspecific resistance. These results demonstrate that, in addition to controlling specific immune responses, genetic differences influence the nonspecific protective phenomena related to BCG administration as well.     

Variability in empathic fear response among 11 inbred strains of mice

Empathy is an important emotional process that involves the ability to recognize and share emotions with others. We have previously developed an observational fear learning (OFL) behavioral assay to measure empathic fear in mice. In the OFL task, a mouse is conditioned for context‐dependent fear when it observes a conspecific demonstrator receiving aversive stimuli. In the present study, by comparing 11 different inbred mouse strains that are commonly used in the laboratory, we found that empathic fear response was highly variable between different strains. Five strains – C57BL/6J, C57BL/6NTac, 129S1/SvImJ, 129S4/SvJae and BTBR T⁺ Itpr3^tf/J – showed observational fear (OF) responses, whereas AKR/J, BALB/cByJ, C3H/HeJ, DBA/2J, FVB/NJ and NOD/ShiLtJ mice exhibited low empathic fear response. Importantly, day 2 OF memory was significantly correlated with contextual memory in the classical fear conditioning among the 11 strains. Innate differences in anxiety, locomotor activity, sociability and preference for social novelty were not significantly correlated with OFL. Interestingly, early adolescent C57BL/6J mice exhibited an increase in acquisition of OF. The level of OFL in C57BL/6J strain was not affected by sex or strains of the demonstrator. Taken together, these data strongly suggest that there are naturally occurring OFL‐specific genetic variations modulating empathic fear behaviors in mice. The identification of causal genes may uncover novel genetic pathways and underlying neural mechanisms that modulate empathic fear and, ultimately, provide new targets for therapeutic intervention in human mental disorders associated with impaired empathy.     

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.     

Studies on pulmonary aryl hydrocarbon hydroxylase activity in inbred strains of mice.

Pulmonary and hepatic levels of aryl hydrocarbon hydroxylase (AHH) were studied in inbred strains of mice following intratracheal (i.t.) instillation of 3-methylcholanthrene (MCA). I.t. instillation of 188 mug MCA in sterile 0.2% gelatin in saline resulted in preferential induction of pulmonary AHH. After treatment with this dose of MCA, the pulmonary AHH levels of strains C57BL/6Cum, C57BL/6J, BALB/cMai, C3H/fMai, and C57L/J were observed to be induced within 24 h after treatment. Strains DBA/2Cum, AKR/J, SJL/J, DBA/2J and RF/J expressed no such increase. At a dose of 500 mug MCA, the pulmonary tissue of DBA/2 mice did express a 4-fold increase. This increase in AHH was determined to be quite different from the increase observed in C57BL/6 mice by: (1) specific activity of the enzymes, (2) genetic regulation, (3) susceptibility to inhibition by 7,8-benzoflavone, and (4) spectral properties of the associated cytochromes. It was of major importance that induction of pulmonary AHH was observed to be regulated by a single dominant gene in crosses involving the C57BL/6Cum and DBA/2Cum strains of mice. Results were discussed with the view in mind that these genetically regulated levels of AHH may play a role in susceptibility to cancers induced by polycyclic aromatic hydrocarbon carcinogens.     

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.     

Variation in nicotine consumption in inbred mice is not linked to orosensory ability

Genetic studies of nicotine addiction in mice have utilizedthe oral self-administration model. However, it is unclear ifstrain differences in nicotine consumption are influenced byvariation in bitter taste sensitivity. We measured both nicotineconsumption and nicotine brief-access licking behavior in severalcommonly used inbred strains of mice that were previously shownto differ in nicotine consumption. A/J (A), C57BL/6J (B6), andDBA/2J (D2) mice were given a 2-bottle choice test with a singleconcentration of nicotine (75 µg/ml; nicotine vs. water).Mice of these strains were also tested with a range of nicotineconcentrations (5–400 µg/ml) using a brief-accesstest, which measures orosensory response and minimizes postingestiveeffects. Although B6 mice consumed more 75-µg/ml nicotinethan A or D2 mice in the 2-bottle test, these strains did notdiffer in level of aversion to nicotine when tested with thebrief-access procedure. Strain differences in orosensory responseto nicotine were not found; yet, differences emerged duringthe 2-bottle tests. This study provides evidence that variationin intake level of nicotine is likely not due to differencesin taste or trigeminal sensitivity but likely due to postingestivefactors.     

Kinetics of ectromelia virus (mousepox) transmission and clinical response in C57BL/6j, BALB/cByj and AKR/J inbred mice

Research was undertaken to answer basic questions on susceptibility, clinical response and transmission of ectromelia virus in selected strains of inbred mice. C57BL/6J and AKR/J were found to be markedly more resistant to a virulent strain of ectromelia virus (isolated during the 1979-80 outbreak at the National Institutes of Health) than C57LJ, BALB/cByJ, DBA/2J, A.By/SNJ and C3H/HeJ when infected by footpad inoculation. In C57BL/6J and AKR/J the LD50 was about 7 logs higher than the ID50. With one exception, C57LJ, the LD50 and ID50 titers in the other strains were about equal. In C57LJ the LD50 titer was intermediate. Following intragastric inoculation, virus was isolated from feces of C57BL/6J mice for as long as 46 days and up to 29 days from BALB/cByJ mice. Transmission to cage mates from intragastrically infected C57BL/6J and BALB/cByJ occurred up to 36 and 30 days respectively after infection. Virus was isolated from the spleen in 2 of 5 BALB/cByJ mice and 1 of 7 C57BL/6J mice tested 95 days after gastric inoculation. Following footpad inoculation, BALB/cByJ mice consistently transmitted virus to cage mates before death at 10-12 days. C57BL/6J mice transmitted between days 8 and 17, but not beyond. Virus was maintained in C57BL/6J mice by exposure to infected cage mates for seven passages, which was the most attempted. Clinical signs in infected C57BL/6J mice were usually subtle or inapparent.