Passive-avoidance performance in mice: evidence for single-locus inheritance

Enhancement of anxiety, facilitation of avoidance behavior, and occurrence of adult-onset obesity in mice lacking mitochondrial cyclophilin D

In this report, we have assessed the behavioral responses of mice missing the Ppif gene (CyPD-KO), encoding mitochondrial cyclophilin D (CyPD). Mitochondrial CyPD is a key modulator of the mitochondrial permeability transition which is involved in the regulation of calcium- and oxidative damage-induced cell death. Behavioral screening of CyPD-KO mice (ranging between 4 and 15 months of age) was accomplished using a battery of behavioral paradigms which included testing of motor functions, exploratory activity, and anxiety/emotionality, as well as learning and memory skills. We found that, compared with wild-type mice, CyPD-KO mice were (i) more anxious and less explorative in open field and elevated plus maze and (ii) performed better in learning and memory of avoidance tasks, such as active and passive avoidance. However, the absence of CyPD did not alter the nociceptive threshold for thermal stimuli. Finally, deletion of CyPD caused also an abnormal accumulation of white adipose tissue resulting in adult-onset obesity, which was not dependent on increased food and/or water intake. Taken together, our results suggest a new fundamental role of mitochondrial CyPD in basal brain functions and body weight homeostasis.

Strain differences in activity and emotionality do not account for differences in learning and memory performance between C57BL/6 and DBA/2 mice

This study examined emotionality, activity, learning and memory, as well as the influence of emotionality and activity on learning and memory performance in C57BL/6 and DBA/2 mice using a mouse-test battery. DBA/2 mice performed more poorly than C57BL/6 mice in complex learning tasks such as the water maze and object recognition tasks. In contrast, C57BL/ 6 mice showed attenuated habituation tonovelty in the open field apparatus and poorer performance in the step-down passive avoidance task. The C57BL/6 mice were less exploratory and more anxious than the DBA/ 2 mice. The anxiety score (open arm entries in the elevated plus maze) was significantly correlated with all measures of learning and memory in the object recognition task, and some measures in the passive avoidance and water maze tasks. Analysis of covariance (with open arm entries as a covariate) revealed that some measures on trial 1 of the object recognition task, but not the memory scores on trial 2,were confounded by anxiety. No confounding factors of anxiety were found in the water maze or passive avoidance tasks. Similar results were obtained with the activity scores (line crossing and rearing in the open field). In conclusion, strain differences in activity and anxiety did not account for strain differences in learning and memory performance of C57BL/6 and DBA/2 mice. Nonetheless, the importance of using complete behavioural test batteries should be stressed to ensure that strain differences in learning and memory tasks are not confounded by non-cognitive factors.

Maternal behavior in female C57BL/6J and DBA/2J inbred mice

Inbred strains of mice exhibit different patterns of maternal behavior, providing material for studies of genetic influences on the expression of maternal behavior. Beginning 1 day after birth, maternal behavior was recorded daily for 14 days in the first and second litters of C57BL/6J (B6) and DBA/2J (D2) mothers. D2 mice had higher pup survival than B6 mice, and pup survival was higher in both strains in second litters than in first litters. D2 mothers spent more time engaged in maternal behavior, especially resting with, crouching over, and nursing pups than B6 mothers with first litters, but not with second litters. Not all measures of maternal behavior were correlated with pup survival; with both litters, B6 mothers retrieved pups faster than D2 mothers.

Effects of situational variables on performance of inbred mice in active- and passive-avoidance situations

A group of experiments were conducted to assess the interaction between environmental factors and specific genetic loci upon the performance of mice in avoidance learning situations. The performance of all mice was better in passive-avoidance than in active-avoidance situations. The performance of C57BL/6J mice was generally superior to that of DBA/2J mice. C57BL/6J mice usually avoided foot-shocks, while DBA/2J mice attempted to escape them. DBA/2J mice performed poorly in the presence of mild foot-shocks, while C57-BL/6J mice performed poorly in the presence of intense foot-shocks. Analysis of the data suggested that the loci involved probably exerted their influence by affecting the subject's response to its environment.

Behavioral characteristics of C57BL/6J. DBA/2J, and B6D2F1 mice which are potentially useful for gerontological research

This review summarizes the behavioral characteristics of C57BL/6J, DBA/2J, and B6D2F1, hybrid mice which are most likely to be of interest to gerontological scientists. Where possible, the characteristics of young and old mice are included. Where no information exists about the behavior of older mice of these genotypes, but there is reason to believe that information about mice might be useful for aging research, this information is included. The purpose of the review is to acquaint gerontologists with the availability of genetically defined animal models for aging research, to present what is known about these models, and to suggest areas of research which could profit from more attention.

Avoidance learning, behavior genetics, and aging: a critical review and comment on methodology

Animal models of human aging problems are potentially of enormous value to gerontological research. Models of behavioral problems have not often lived up to their promise. This review examines one such model system, avoidance learning in aging rodents. This model system has become increasingly popular among behavioral gerontologists, yet it has not provided the unambiguous answers to experimental questions which investigators expected. Our effort has been to determine why the system has failed, and to provide useful suggestions for future research. At the same time we have tried to provide a comprehensive review of the relevant literature and to assess the strengths and weaknesses of studies which have been conducted in the last two decades.

Genetic analysis of water maze discrimination learning for Mus musculus: polygenes and albinism

Recombinant inbred strains, their progenitor strains and reciprocal F1 hybrids were given thirty spatial discrimination learning trials in the water maze. The pattern of RI strains in relation to the reciprocal F1 hybrids and the progenitor strains, and differences among strains, suggested that different sets of genes affect the various components of water maze discrimination learning. There was no evidence that the albino gene influenced either inferior or superior performance. Pigmented strains performed as well as, or better than, some albino strains, and albino strain BALB/cBy differed significantly from albino strains CXBG and CXBI. The two reciprocal F1 hybrids differed from blocks 2 and 3 of discrimination trials when swimming time was used a dependent variable. Thus, it appears that performance of the F1 hybrids was influenced by paternal effects, maternal effects, or paternal maternal interactions.

Maze learning: a genetic investigation in the mouse

Recombinant inbred strains, their progenitor strains, and their reciprocal F1 hybrids were tested for maze learning in the Lashley III maze and in the Y-water maze. The resulting pattern of strain distribution suggested that the genetic model provided by the RI strains is based on at least two, and possibly many more, loci. There was no evidence of maternal effects or heterosis. Although the BALB/cBy strain represented an extremely high scoring strain for the Lashley maze and a low scoring strain for the Y-maze, presence of albino recombinant inbred strains intermediate to extreme strains and nonsignificantly different from pigmented recombinant inbred strains suggested that the albino gene was not responsible for the observed performance differences.

Genetic analysis of active avoidance performance in mice

Mice of two inbred strains, C57BL/6J and DBA/2J, and the F1 hybrid of a cross between them were trained in an active avoidance jump-up task under distributed practice conditions. Significant differences in the performance of mice of the two strains were observed, with relatively poor performance by DBA/2J mice and relatively good performance by C57BL/6 mice. The performance of F1 hybrid mice did not differ significantly from DBA/2J mice. Crosses were made to produce segregating generations of mice. Their performance supported a single-locus model of inheritance for active avoidance jump-up behavior. Under these experimental conditions the dominant allelle (Aapd) was associated with poor performance while homozygosity for the recessive allele (Aapb) was associated with superior performance.