Behavioral studies using genetically defined mice. A bibliography

Out of the bottleneck: the Diversity Outcross and Collaborative Cross mouse populations in behavioral genetics research

The historical origins of classical laboratory mouse strains have led to a relatively limited range of genetic and phenotypic variation, particularly for the study of behavior. Many recent efforts have resulted in improved diversity and precision of mouse genetic resources for behavioral research, including the Collaborative Cross and Diversity Outcross population. These two populations, derived from an eight way cross of common and wild-derived strains, have high precision and allelic diversity. Behavioral variation in the population is expanded, both qualitatively and quantitatively. Variation that had once been canalized among the various inbred lines has been made amenable to genetic dissection. The genetic attributes of these complementary populations, along with advances in genetic and genomic technologies, makes a systems genetic analyses of behavior more readily tractable, enabling discovery of a greater range of neurobiological phenomena underlying behavioral variation.

Delineation of violence from functional aggression in mice: an ethological approach

The present study aims at delineating violence from aggression, using genetically selected high (SAL, TA, NC900) and low (LAL, TNA NC100) aggressive mouse strains. Unlike aggression, violence lacks intrinsic control, environmental constraints as well as functional endpoints. Conventional measures namely latency, frequency and duration were used initially to accomplish the objective of delineation using the above strains. However, these quantitative measures fail to reveal further details beyond the magnitude of differential aggression, especially within the high aggressive mouse strains. Hence, it was necessary to analyze further, the behavioral sequences that make up the agonistic encounter. Novel measures such as threat/(attack + chase) (T/AC) and offense/withdrawal (O/W) ratios, context dependency and first-order Markov chain analysis were used for the above purpose. Our present analyses reveal clear qualitative behavioral differences between the three high aggressive selection strains based on the following facets namely structure and context in an agonistic interaction. Structure refers to a detailed study of the agonistic interaction components (ritualistic display, offense and sensitivity to the opponent submission cues) between any two subjects (inter-male interaction for the present study). Context refers to the capacity to identify an opponent by nature of its state (free moving/anesthetized), sex and the environment (home/neutral territory). NC900 displayed context dependency and structurally a rich repertoire of agonistic interaction components with an opponent. SAL failed to show discrimination and its inter-male agonistic behavior is restricted to a repetitive and an opponent-insensitive pattern of attack and chase. TA was comparable to SAL in terms of the structure but sensitive to context variables. Thus, SAL seems to display a violent form of aggressive behavior, while NC900 display 'functional' hyperaggression against a docile opponent in an inter-male agonistic interaction.

The genetics of g in human and mouse

The g factor refers to the substantial overlap that exists between individual differences in diverse cognitive processes in humans. In this article, I argue that a mouse model of g could provide a powerful analytic tool for exploring cognitive processes that are linked functionally by genes.

Use of SHIRPA and discriminant analysis to characterise marked differences in the behavioural phenotype of six inbred mouse strains

Detailed characterisation of six inbred strains of mice commonly used in transgenic and knockout research was carried out using a battery of behavioural tests (SHIRPA) followed by discriminant analysis of the data. In the primary observation screen, DBA/2 mice were relatively irritable and vocalised during handling. C57BL/6 were hyperactive as measured by transfer arousal, arena activity and touch-escape tests. By contrast, C3H were markedly hypoactive, had significantly enhanced grip strength and were also significantly impaired on the visual placing task. In the elevated plus-maze, BALB/c mice showed the highest level of open arm entries and time spent in the open arms, indicating the lowest level of anxiety. There was a clear dissociation of strains on exploratory activity, as measured in the holeboard test and spontaneous locomotor activity (LMA). DBA/2 mice were hyperactive in LMA but demonstrated relatively low levels of holeboard exploration. None of the six strains learnt the water maze spatial learning task particularly well. C57BL/6 and 129/Sv demonstrated most ability and C3H showed no evidence of having acquired the task. The SHIRPA screening battery and discriminant analysis of the data have enabled us to determine the relevant contribution of a number of behavioural measurements to the marked differences in phenotype of mouse strains. These data confirm the importance of carrying out a comprehensive profile in order to accurately characterise the phenotype of gene-targeted and transgenic mice.

A proposed test battery and constellations of specific behavioral paradigms to investigate the behavioral phenotypes of transgenic and knockout mice

Behavioral phenotyping of transgenic and knockout mice requires rigorous, formal analyses. Well-characterized paradigms can be chosen from the established behavioral neuroscience literature. This review describes (1) a series of neurological and neuropsychological tests which are effectively used as a first screen for behavioral abnormalities in mutant mice, and (2) a series of specific behavioral paradigms, clustered by category. Included are multiple paradigms for each category, including learning and memory, feeding, analgesia, aggression, anxiety, depression, schizophrenia, and drug abuse models. Examples are given from the experiences of the authors, in applying these experimental designs to transgenic and knockout mice. Extensive references for each behavioral paradigm are provided, to allow new investigators to access the relevant literature on behavioral methodology.

What can genetic models tell us about behavioral plasticity?

Biological diversity and learning have played an essential interactive role in the evolution of species, as intra-specific individual differences have exerted a buffering effect towards environmental changes, and learning ability per se has allowed their maintenance. By exploiting biological diversity individuals with defective learning and memory have been produced that allow the study of the neural substrates of encoding mechanisms, as has been done in studies from Drosophila to rodents. Various aspects of this neurogenetic approach are reviewed and pitfalls are indicated. It is clear that genetic models need to be implemented by an integrated multidisciplinary top-down approach based on behavioral, electrophysiological, histochemical, immunocytochemical and neurochemical techniques. Examples are presented from some animal models that illustrate how a systems level analysis of the neural substrates of information processing can be carried out using such an integrated scheme.

Using genetically-defined rodent strains for the identification of hippocampal traits relevant for two-way avoidance behavior: a non-invasive approach

Genetically-defined rodent strains permit the identification of hippocampal traits which are of functional relevance for the performance of two-way avoidance behavior. This is exemplified here by analyzing the relationship between infrapyramidal mossy fibers (a tiny projection terminating upon the basal dendrites of hippocampal pyramidal neurons) and two-way avoidance learning in about 800 animals. The necessary steps include 1) identification of structural traits sensitive to selective breeding for extremes in two-way avoidance, 2) testing the robustness of the associations found by studying individual and genetical correlations between hippocampal traits and behavior, 3) establishing causal relationships by Mendelian crossing of strains with extreme structural traits and studying the behavioral consequences of such structural 'randomization', 4) confirming causal relationships by manipulating the structural variable in inbred (isogenic) strains, thereby eliminating the possibility of genetic linkage, and 5) ruling out the possibility of spurious associations by studying the correlations between the hippocampal trait and other behaviors known to depend on hippocampal functioning. In comparison with the classical lesion approach for identifying relationships between brain and behavior, the present procedure appears to be superior in two aspects: it is non-invasive, and it focuses automatically on those brain traits which are used by natural selection to shape behaviorally-defined animal populations, i.e., it reveals the natural regulators of behavior.

Different effects of 3-chlorophenylpiperazine on locomotor activity and acquisition of conditioned avoidance response in different strains of mice

Mice of C57BL/6 (C57), Balb/c (BALB), and CD-1 (CD) strains were injected with 3-chlorophenylpiperazine (CPP), 1-10 mg/kg ip, and their exploratory and basal locomotor activities and acquisition of conditioned avoidance response in a shuttle-box were tested. In C57 mice CPP did not affect either locomotor activity or shuttle-box performance. In BALB mice CPP inhibited both basal and exploratory activities (the latter only in higher doses) and facilitated the acquisition of conditioned avoidance response. In CD mice CPP did not affect exploration, but inhibited basal locomotor activity and facilitated the shuttle-box performance. It is concluded that there exist large interstrain differences in responsiveness of mice to CPP, and that the drug may facilitate acquisition of conditioned avoidance response through a strain-specific, serotonin-independent mechanism.

A fit mouse is a hoppy mouse: jumping behavior in 15-day-old Mus musculus

An analysis of a juvenile hopping response from an 8 X 8 diallel cross is used to demonstrate the experimental genetic approach for testing presumed adaptive fitness of behaviors in developing organisms. In accordance with predictions, the explosive jumping behavior exhibited by 15-day mice is characterized by a pattern of genetic dominance toward high expression of the trait. Wild mice show even more vigorous responses, indicating that selection pressures maintaining high responding have been relaxed during domestication. These data suggest some applications and limitations of genetic methods for the study of behavioral evolution as related to development.

An overview of neurobiological comparisons in mouse strains

A literature review of research dealing with mouse strain comparisons along neurobiological parameters is presented in tabular form which provides a rank-ordering of strains and estimates of percentage differences in individual parameters. Drawing from 86 references, three tables deal respectively, with comparisons of neurochemical, neuroanatomical, and neuropsychophysiological parameters.

The effect of varying doses of d-amphetamine on activity levels of prepubertal mice

The effect of varying doses of d-amphetamine on the activity level of C57BL/6J mice (known for their high activity level), DBA/1J, C3H/HeJ, and C3D2F1 mice was investigated (all mice were 25 to 30 days old). Activity was measured by the use of an activity cage with a revolving drum. After determination of baseline activity level, the animals were assigned to the following set of i.p. injections: (1) normal saline, (2) d-amphetamine 0.2 mg/kg, (3) d-amphetamine 0.5 mg/kg, (4) d-amphetamine 5 mg/kg. The mean activity level of the C57BL/6J mice was significantly higher than that of the other strains. The mean activity level after 5 mg/kg was significantly lower than after other dosages in all strains. All strains responded similarly to d-amphetamine as is apparent from the parallel profiles for the dose-response curves. The response of the developing mice to d-amphetamine is at variance with the known response of mature mice.

Effect of clonidine, amphetamine, and their combinations on the locomotor activity of CD-1 and C57BL/6 mice

Clonidine inhibited the exploratory motor activity of C57BL/6 mice non-habituated to the testing conditions. In CD-1 mice clonidine did not depress exploratory activity but did elevate the basal locomotor activity of animals both non-habituated and habituated to testing conditions. Amphetamine increased the locomotor activity of many C57BL/6 mice and conversely inhibited the locomotion of many CD-1 mice. In both strains, amphetamine in doses up to 2 mg/kg was unable to alter effects produced by clonidine. Results suggest that the locomotor activity of C57BL/6 mice is more sensitive than that of CD-1 mice to drugs affecting the central noradrenergic system.

Technique for assessing visual discrimination learning in mice

An automated technique for the study of visual discrimination learning in mice has been developed. The technique utilizes a nose-poke as the operant response. The nose-poke response requires no shaping, has a relatively high operant level and can be used to measure preacquisition exploratory behavior. CD-1 mice acquired a simultaneous brightness discrimination readily but a successive brightness discrimination proved more difficult. A 20 sec intertrial interval was optimal for acquisition of the simultaneous discrimination. Reversal learning was slow. This procedure should prove useful in the study of the effects of pharmacologic and toxic agents on learning and performance in both weanlings and adult mice.

Regional acetylcholine turnover rates in the brains of three inbred strains of mice: correlation with some interstrain behavioural differences

The hypothesis that the genetically determined behavioural differences which exist between the inbred mouse strains Balb/c, DBA/2 and C57Bl/6 may be related to differences in acetylcholine metabolism in certain regions of the brain has been tested. In vivo ACh turnover rates have been measured in three regions (hippocampus, caudate nucleus and frontal-parietal cortex) of the brains of each strain by following the rate of formation of labelled ACh, in these regions, after a pulse intravenous injection of a tracer dose of 3H labelled choline. Focused microwave procedures were used for the rapid fixation of brain tissue and Ch and ACh radioactivities were determined following their electrophoretic separation. Steady-state concentrations of Ch and ACh were measured by a sensitive radio-enzymatic method. Significant interstrain differences in ACh turnover rates are reported for each of the brain regions studied with the order of metabolic activity being Balb/c greater than DBA/2 greater than C57 Bl/6 in each case. These results are interpreted as being in agreement with previous reports on correlations between learning ability or locomotor activity and regional activities of choline acetyltransferase in the brains of these inbred strains. The correlations between the in vivo ACh turnover rates and (1) interstrain differences in behavioural measures and (2) regional choline acetyltransferase activities are discussed.

Multivariate and behavior genetic analysis of avoidance of complex visual stimuli and activity in recombinant inbred strains of mice

Sixty-six mice of 11 genetic stocks (the Bailey recombinant inbred strains CXBD, CXBE, CXBG, CXBH, CXBI, CXBJ, CXBK; their progenitor strains, BALB/cBy and C57BL/6By: and the reciprocal hybrids, B6CF and CB6F) were tested in a two-compartment apparatus and in a shuttlebox, with five measures taken relating to activity and to approaches to novel and complex stimuli. A factor analysis of these measures revealed two factors, the first involving behavior relating to novel stimuli and the second relating to locomotor activity. In a second experiment, 132 mice of the same strains were tested on four of the measures used previously. On the two measures which had high loadings on the first factor and very low loadings on the second, it was possible to determine a strain distribution pattern (SDP), with the same SDP being found for both measures. When confirmed by testing mice from two congenic histocompatibility strains H(w54) and H(w80), we were able to determine that avoidance of novel/complex stimuli (neophobia) is controlled by a gene or genes at chromosomal segments H-24c and H-1b. It was also found that a polygenic model is consistent with behavior measured by the second (activity) factor.

Genetic variation in brain L-glutamate decarboxylase activity from two inbred strains of mice

Two inbred strains of mice, C57BL/6Bg and DBA/1Bg, were compared for genetic varaition in brain L-glutamate decarboxylase (GAD) activity. Although no large difference was found between the strains in whole brain GAD activity at adult age (27--45 days postnatally), regional examination revealed a difference in GAD activity in the cerebral cortex (15% higher in DBA); subcellular examination revealed a difference in synaptosomal fraction (21% higher in DBA). When GAD activity was measured in synaptosomal fractions prepared from dissected cerebral cortex, DBA was 34% higher than C57BL. In addition, differences in GAD activity between the two strains could be observed even in the whole brain (10--15% higher in DBA) during earlier development (15--23 days postnatally). These data indicate that at adult age, genetic difference in GAD activity between the two strains exists mainly in nerve terminals of the cerebral cortex. It is postulated that the difference may be due to a genetically mediated mechanism regulating GAD in the presynaptic terminals of GABA neurons of the cerebral cortex.

Effects of stimulus intensity and stimulus duration during acoustic priming on audiogenic seizures in C57BL/6J mice

The effects of stimulus intensity and stimulus duration were examined in C57BL/6J mice not susceptible to audiogenic seizures (AGS) on the 1st exposure to an acoustic stimulus. Two experiments were performed. In the 1st, 16-day-old mice were exposed to 108, 112, 120, or 127 dB for 60 sec. Mice were then tested for susceptibility to AGS at varying ages thereafter. Increasing intensity of noise during priming resulted in heightened peak seizure risk, and extended duration of peak seizure risk, and a prolonged time of seizure risk. In the 2nd experiment, mice were exposed for 5, 15, 30, or 60 sec to 127 dB of noise. Five seconds of noise was barely sufficient to induce later susceptibility to AGS. Increasing stimulus duration from 15 to 30 to 60 sec resulted in increasing seizure risk and duration of peak risk period.