Developmental differences in place-learning performance between C57BL/6 and DBA/2 mice parallel the ontogeny of hippocampal protein kinase C.

This study determined the ontogenic changes in learning and hippocampal protein kinase C (PKC) in C57 and DBA mice. Mice were tested on the visible- or hidden-platform versions of the Morris water task starting at 17, 24, 31, or 60 days of age. Both strains learned to locate the visible platform at all ages. C57 mice learned to solve the hidden-platform task when they were 24 days old, whereas DBA mice never learned to solve this task. Using a [–3H]-phorbol ester binding assay, the authors found that both strains had similar amounts of hippocampal PKC at 10 and 17 days of age but that C57 mice had significantly more PKC at 24, 31, and 60 days of age. Immunoblotting results revealed that C57 mice had more γ-PKC, but not α-PKC, than DBA mice. Thus, the development of performance differences in spatial learning between C57 and DBA mice parallels the ontogeny of hippocampal PKC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparative genetic analysis of the role of the brain dopaminergic systems in the regulation of behavioral elements in the "open field" test in DBA/2J and C57BL/6J mice

The effects of intraperitoneal injections of sulpiride (10 mg/kg), bromocriptine (5 mg/kg), and alaptide (1 mg/kg) on the behavior of male C57BL/6J (C57BL) and DBA/2J (DBA) mice in the open-field test were studied. In this test, C57BL mice exhibited a significantly higher horizontal locomotor activity than DBA mice, whereas DBA mice moved in place substantially longer than C57BL mice. Dopaminergic agents had different effects on the open-field behavior in different mouse strains. Alaptide increased horizontal locomotor activity in DBA, but not in C57BL mice; all the three agents decreased the duration of movement in place in DBA but not in C57BL mice; bromocriptine suppressed vertical locomotor activity and the act of looking into holes in C57BL but not in DBA mice. Thus, interstrain differences in dopaminergic functions were demonstrated. The revealed strain-specific characteristics largely contribute to the determination of open-field behavior in the studied mouse strains.     

Strain distribution of mice in discriminated Y-maze avoidance learning: Genetic and procedural differences.

The current study was conducted to characterize discriminated avoidance learning in mice by using a Y-maze task. In Experiment 1, the task parameters were manipulated, including the amount of time spent in the start arm, the amount of time to make the avoidance response, and the intertrial interval (ITI) using C57?×?SJL F1 hybrid mice. Avoidance performance was significantly improved with longer times to avoid the shock and longer ITIs. In Experiment 2, mice from 4 inbred strains (BALB/cByJ, DBA/2J, C57BL/6J, and SJL/J), an F1 hybrid (C57?×?SJL), and 1 outbred strain (CD1) were tested with various ITIs. Strain differences were observed in avoidance learning, with BALB, DBA, C57?×?SJL and CD1 mice showing significantly better avoidance learning than C57 mice, which were better than SJL mice. These data demonstrate that Y-maze performance is significantly influenced by the genetic background of the mouse and the parameters of the task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral sensitization to drug stimulant effects in C57BL/6J and DBA/2J inbred mice.

Common features shared by addictive drugs have been difficult to identify. One ubiquitous effect of these drugs is psychomotor stimulation. Further, repeated exposure commonly results in sensitization to drug stimulant effects. This study evaluates sensitization to drugs from several drug classes in C57BL/6J and DBA/2J inbred strain mice. DBA/2J mice showed sensitized responses to ethanol and methamphetamine, whereas C57BL/6J mice developed sensitization to morphine and methamphetamine. Strain susceptibilities to ethanol- and morphine-induced sensitization closely paralleled their sensitivities to the acute stimulant effects of these drugs; this was not the case for methamphetamine. The relative sensitivities of DBA/2J and C57BL/6J mice were not consistent across drugs, suggesting that the stimulant and sensitized responses to these drugs may be mediated by at least partially divergent neural mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hippocampal lesions cause learning deficits in inbred mice in the Morris water maze and conditioned-fear task.

This study examined the effect of hippocampal lesions on acquisition of the Morris water maze and conditioned-fear task in inbred mice. C57BL/6J, DBA/2J, and B6D2F1 hybrid mice were given hippocampal lesions or sham surgery and then tested. The lesioned C57BL/6J and B6D2F1 mice failed to learn the Morris task relative to sham-operated controls, and no DBA group learned the task. In the contextual component of conditioned fear, lesions decreased freezing in all strains. But the lesions only affected freezing to the conditioned stimulus in the DBA/2J and B6D2F1 strains. These data demonstrate that C57BL/6J and B6D2F1 mice use the hippocampus to solve the Morris water maze and conditioned-fear task, and the DBA mice use the hippocampus, to some degree, in the conditioned-fear task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of multiple behavioral effects between olfactory bulbectomized C57Bl/6J and DBA/2J mice

The behavioral effects of bulbectomy and subsequent antidepressant treatment in two mice strains were compared on measures of open field behavior and passive and active avoidance 2 and 4 weeks after surgery. After bulbectomy, both strains displayed elevated locomotion in open field, corrected by antidepressants. Enhanced rearing was decreased by antidepressants in C57Bl/6J, but not in DBA/2J mice. Passive avoidance, being intact 2 weeks after surgery in both strains, was strongly impaired 4 weeks after bulbectomy in C57Bl/6J mice, with antidepressants restoring the performance. Active avoidance acquisition and retention were also dramatically disturbed in C57Bl/6J mice 2 and 4 weeks after surgery, and antidepressants had recuperative effect. In contrast, bulbectomized DBA/2J mice didn't show any significant passive or active avoidance deficits, and antidepressant treatment seemed to have no effect on their learning ability. The observed strain differences suggest that bulbectomy may produce quite diverse neurophysiological and neurochemical alterations in two strains.     

Genotype-dependent effects of septal lesions on different types of learning in the mouse.

Tested 80 C57BL/6J, DBA/2J, and SEC/1ReJ mice with septal or control lesions for exploratory behavior, shuttle-box avoidance learning, discriminated avoidance, and maze-learning ability. Control DBA and SEC Ss normally displayed low levels of exploratory behavior and efficient avoidance and maze learning. High exploratory activity and low avoidance and maze learning were characteristically shown by C57 controls. All strains with septal lesions increased levels of exploratory and avoidance behaviors. In contrast, following septal lesions the 3 strains performed more poorly in discriminated-avoidance and maze learning. It is concluded that differences in septal function-e.g., in level of response inhibition-do not substantially account for the learning differences evident between these strains. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task-dependent genetic influences on behavioral response of mice (Mus musculus) to acetaldehyde.

Employed acetaldehyde as a pharmacological agent in behavioral tests designed to assess genetic influences on response to the drug. When used as a poison in a conditioned taste aversion study with 200 male mice, acetaldehyde was more effective at inducing aversions in DBA/2J mice than in C57BL/6J mice. In another experiment, however, 6 C57 mice were more affected than were 6 DBA mice by acetaldehyde effects on loss of righting reflex. Implications for postulated genetic control of ethanol preference and neurosensitivity are discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in learning and memory in mice: Effects of sequence of testing and cholinergic blockade.

Sexual dimorphism in spatial and cued navigation using the Morris water maze was examined in C57BL/6 mice both with and without administration of scopolamine, a cholinergic blocker. In Exp 1, female and male mice learned to perform first a spatial, then a cued, navigation task. Both performed a spatial task similarly; males, however, performed a cued task better than females. In Exp 2, the sequence of navigation testing was reversed. Both performed similarly on a cued task; however, males performed a spatial task better than females. In both experiments, females were more sensitive than males to the effects of scopolamine. No significant confounding sex differences were found in either spontaneous activity or passive avoidance retention. These data indicate that sex differences in spatial and cued tasks are dependent on the sequence of task presentation and implicate a role for the cholinergic system in these differences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

DBA/2 and C57BL/6 mice differ in contextual fear but not auditory fear conditioning.

It has been proposed that DBA/2 and C57BL/6 mice perform differently on some learning and memory tasks because of functional differences in the hippocampal formation. To evaluate this hypothesis, DBA/2 and C57BL/6 male mice were tested on 2 forms of conditioned fear: contextual fear conditioning, which depends on the integrity of the hippocampal formation, and auditory cue conditioning, which does not. Both mouse strains displayed equivalent conditioning when the auditory cue was paired with shock, but DBA/2 mice showed significantly less conditioning to the context in which shock was experienced. These results are consistent with the hypothesis that the pattern of spared and impaired performance, which DBA/2 mice display on a variety of learning and memory tasks, is related to impaired hippocampal formation function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mice: Progesterone and the regulation of strain differences in pregnancy-induced nest building.

Four experiments with 113 C57BL/6J and 80 DBA/2J female mice showed that pregnant DBA/2J Ss built significantly larger and more completely enclosed nests than did pregnant C57BL/6J Ss. This strain difference was restricted to the last half of gestation and was not observed during either the virgin state or lactation. Genotype-based differences in pregnancy-induced nest building were not related to circulating levels of progesterone (P), core temperature, or body weight. Exposure to supplemental P (100, 200, or 400 μg, sc) during pregnancy elevated nest building exhibited by pregnant C57BL Ss but did not induce DBA-like levels of the behavior. Also, virgin DBA Ss built larger nests in response to P than did C57BL Ss. Findings suggest that differences in the sensitivity of central neural tissue to steroid hormones may account for genotypically determined variation in patterns of pregnancy-induced nest building. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of alcohol on acquisition and retention of passive-avoidance conditioning in different mouse strains.

270 male Ss of the C57BL/6 and DBA/2 inbred mouse strains and of the F1 hybrid of these 2 were trained and tested in a passive-avoidance task under 0-3 gm/kg doses of ethanol. The C57 Ss performed better in acquisition at higher alcohol doses than either the DBA or hybrid Ss. The hybrids showed retention the following day at higher doses than either of the parental strains. The DBA and C57 Ss showed evidence of state-dependent learning at some alcohol doses while the hybrid mice did not. Low doses markedly disinhibited DBA mice in initial exploratory behavior, so that they became identical in this parameter to the other strains which were not so affected. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Segregation analysis of the testis-determining autosomal trait, Tda, that differs between the C57Bl/6J and DBA/2J mouse strains suggests a multigenic threshold model

The testis-determining autosomal trait (Tda) of the mouse was uncovered when the Y chromosome of the poschiavinus variety of Mus musculus domesticus was introduced into the C57BL/6J laboratory strain background. Testis development is normal in the F1 generation but, in the backcross and subsequent crosses to C57BL/6J females, XY individuals with the poschiavinus Y chromosome expressed bilateral ovaries or various combinations of an ovotestis with a contralateral ovary or testis or bilateral ovotestes and few had testes bilaterally. In other strain backgrounds, such as DBA/2J, XY individuals with the poschiavinus Y chromosome always expressed normal testes bilaterally. The first breeding analysis of this difference in the interaction of strain background with the poschiavinus Y chromosome suggested that the Tda trait was due to a single gene, but attempts to map it failed. We constructed two strains of C57BL/6J and DBA/2J that are consomic for the poschiavinus Y chromosome in order to conduct a segregation analysis of the Tda trait. In the C57BL/6J.Y-POS consomic strain, liability to express incomplete testis development is normally distributed and thresholds in development specify the probability of different classes of ovary, ovotestis, and testis combinations. Testis development is complete in the DBA/2J.Y-POS consomic strain. We demonstrated previously that the Tda trait of C57BL/6J is recessive to that of DBA/2J and the segregating first backcross generation of embryos rejected the single-gene model. We have extended our analysis to a F2 generation of embryos that also rejects a single-gene model. We also report a test mating analysis of the first backcross generation. It was initiated to provide an independent assessment of the single-gene model, but the analysis of the distribution of test mating results suggests that the difference in the Tda trait between C57BL/6J and DBA/2J may be due to a small number of loci, possibly four or five, and that the phenotypic effect between loci may be additive.     

Generality of learning differences in brain-weight-selected mice.

48 male and 48 female mice representing 8 lines (BALB/cJ, C57BL/6J, DBA/2J, LG/J, LP/J, MA/J, SM/J, and 129/J) from 2 independent selection programs for high, medium, and low brain weight were raised in enriched environments and tested on active avoidance, water maze, operant discrimination, and passive avoidance tasks. Although statistically reliable performance differences were found on each task within at least one selection, there was no consistent relation within selections and across tests or within tests and across selections between brain weight and performance. Results emphasize the need to eliminate confounded performance variables in behavior genetic research on learning phenotypes and suggest that brain weight–learning correlations in mice are either small or nonexistent. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory similarities associated with genetic and experimental acoustic deprivation.

In previous studies, susceptibility to audiogenic seizures has been produced in otherwise nonsusceptible mice by acoustic stress and by conductive hearing loss. Both procedures temporarily elevate the absolute threshold of the auditory evoked potential (AEP) and are maximally effective during a circumscribed period of early development. The present 2 experiments were conducted with 35 DBA/2J and 36 C57BL/6J mice. In the genetically susceptible DBA/2J mouse, AEP thresholds indicated that its auditory system was functionally less mature during this early period than that of the nonsusceptible C57BL/6J mouse. It is proposed that innate susceptibility found in the DBA/2J mouse results from auditory disuse supersensitivity during a critical developmental period, in support of the hypothesis (J. C. Saunders et al) for acoustically primed mice. The increased peak-to-peak AEP amplitudes, however, were not believed to be causally related to the audiogenic seizures. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex-restricted non-Mendelian inheritance of mouse chromosome 11 in the offspring of crosses between C57BL/6J and (C57BL/6J x DBA/2J)F1 mice

We report on the observation of sex-restricted, non-Mendelian inheritance over a region of mouse Chromosome (Chr) 11, occurring in the offspring of crosses between two commonly used Mus musculus-derived inbred strains, C57BL/6J and DBA/2J. In the surviving backcross progeny of reciprocal matings between (C57BL/6J x DBA/2J)F1 hybrids and the C57BL/6J parental strain, we observed the preferential appearance of C57BL/6J alleles along a region of Chr 11. The deviation from Mendelian predictions was observed only in female offspring from both reciprocal backcrosses, and not in males from either cross. The sex-specificity of the observed non-Mendelian inheritance points to an explanation based on embryonic or neonatal lethality. Our data add to previously obtained evidence for a Chr 11 locus or loci with sex-specific and allele-specific effects on viability.     

Contextual and cued fear conditioning in C57BL/6J and DBA/2J mice: Context discrimination and the effects of retention interval.

Context discrimination and time course studies of contextual fear conditioning revealed strain differences between C57BL/6J (B6) and DBA/2J (D2) mice. Both strains discriminated contexts, but D2 mice exhibited less freezing in a shock-paired context. The strains did not differ immediately, or at 2 and 3 hr after contextual fear conditioning training. D2 mice showed less freezing at 15 min, 30 min, and 24 hr after training. B6 mice exhibited exaggerated generalized freezing and poor discrimination between the context and altered context 7-30 days after training. The acoustic startle response in B6 mice was also enhanced at 14 days after training. D2 mice did not show this pattern of generalized freezing. B6, but not D2, mice retained contextual memories for at least 60 days. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predatory behavior in laboratory mice: Strain and sex comparisons.

Measured latency to attack live crickets in 26 male and 26 female naive, non-food-deprived laboratory mice from a genetically heterogenous stock (HS/Ibg) and in 7 inbred strains (10 male and 10 female Ss for each strain). The HS/Ibg, Is/Crgl, C57BL/Crgl, and C3H/Crgl Ss had the shortest latencies to attack crickets. The RIII/Crgl and BALB/cCrgl Ss were intermediate, while DBA/2Crgl and A/Crgl were slowest. Among the inbred strains sex differences were nonexistent or inconsistent from strain to strain. However, HS/Ibg males were more likely to attack than were females. Enough females attack for cricket killing to be a useful form of attack behavior for genetic experiments. In nearly all Ss latency decreased from the 1st to the 2nd trial, indicating that cricket killing is rapidly learned in adult mice of a wide variety of genotypes. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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 dose-dependent 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 aversion 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.     

Suppression of skin reactivity to purified protein derivative by hepatitis C virus among HTLV-I carriers in Japan

Gamma-aminobutyric acid (GABA)A receptors are the sites of action for many antiepileptic drugs such as benzodiazepines and barbiturates. We report the results of molecular cloning of the gamma1-subunit from seizure prone DBA/2J and resistant C57BL/6J inbred mice, and analyses of nucleotide sequences and expression of the gamma1-subunit messenger RNA (mRNA) in DBA/2 and C57BL/6 inbred mice. The mouse gamma1-subunit complementary DNA (cDNA) shares 98% similarity with that of the rat at the level of amino acid sequence. Northern blot hybridization indicates that the gamma1-subunit mRNA is expressed predominantly in areas other than the cerebral cortex and cerebellum and shows little change with postnatal development. No differences have been found for the subunit between DBA/2 and C57BL/6 mice either for nucleotide sequence or for level of expression of the subunit's mRNA in whole brain by Northern blots at 3 weeks of age.