Behavioural analysis and susceptibility to CNS injury of four inbred strains of mice

Interpretation of data from gene targeting studies can be confounded by the inherent traits of the background inbred strains used in the generation of transgenic and null mutant mice. We have therefore compared the behaviour and response to CNS injury of four inbred strains commonly used in molecular genetic studies to produce models of neurological disease. Adult, male 129/Ola, BALB/c, C57BL/6 and FVB/N mice (2–4 months) were initially subjected to behavioural tests that comprised a neurological examination, determination of motor function and cognitive testing in the Morris water maze. Also the response to CNS injury following an acute kainic acid (KA) challenge (30 mg kg⁻¹, i.p.) was determined. The 129/Ola and BALB/c strains showed significant motor deficits when compared with the C57BL/6 and FVB/N strains. In contrast, only the FVB/N strain showed evidence of apparent cognitive impairments in the water maze as evidenced by increased pathlengths to locate the escape platforms and impaired performance in a probe trial. In addition, the FVB/N strain showed the most severe seizure response and mortality rate (62%) following administration of KA (30 mg kg⁻¹, i.p.). These behavioural changes were also associated with a greater degree of cell body and synaptophysin loss in the pyramidal CA3 hippocampal cell layer and astrogliosis 72-h post-dose. These data suggest that the FVB/N strain may not be the most suitable background strain for the development of new transgenic mice for the study of genes implicated in the learning and memory process.     

Genetic diversity underlying capsaicin intake in the Mishima battery of mouse strains

Capsaicin is the active substance responsible for the pungent sensation produced by red pepper. In order to approach the underlying genetic mechanism for preference of red pepper, we conducted a 12-h, 1-bottle intake test of capsaicin solution using both male and female animals from the Mishima battery of mouse strains: 10 wild-derived inbred strains (PGN2, BFM/2, HMI, CAST/Ei, NJL, BLG2, CHD, SWN, KJR, MSM), 1 strain derived from the so-called fancy mouse (JF1), and 3 widely used laboratory strains (C57BL/6J, DBA/1J and BALB/cAnN). The concentration of capsaicin was increased from 0.5 to 15 microM successively. Gender differences were not observed in this test, but we found striking strain differences in capsaicin intake. Relative to baseline water intake, C57BL/6J and DBA/1J consumed 10%, whereas two wild strains, KJR and MSM, ingested approximately 60% of the 15-microM capsaicin solution. In a 2-bottle fluid preference test, both C57BL/6J and MSM strains reject capsaicin fluid even at the 0.5-microM concentration, which indicates that the receptors for capsaicin in these strains recognize capsaicin at a similar level. Thus, the strain differences at higher capsaicin concentrations in the 1-bottle test may reflect differences in central nervous system response to the capsaicin solution. The genetic difference in intake of capsaicin observed in these strains may provide a useful tool for identifying genes underlying response to red pepper in mice and other mammalian species.     

Reliability assessment of an automated forced swim test device using two mouse strains

The Porsolt forced swim test (FST) is one of the most widely used behavioral tests in the evaluation of the antidepressant effects of drugs. It is based on the fact that these drugs reduce the depression-related behaviors of learned helplessness. The model has been modified for use in mice. In contrast to rats, mice are exposed to forced swimming only once and their immobility behavior is measured and considered a "depression-like" phenotype. Like many other behavioral tests, FST can be affected by observer-related artifacts. In recent years, automated testing systems have been developed to decrease artifacts that may greatly influence the interpretation of results. In this work, we used two strains of mice, i.e., C3H/HeJ and C57BL/6J, which differ in their FST immobility times. We employed a new commercially available automated FST device and a blinded observer-based FST, and we examined their ability to measure behavioral differences between these two mouse strains. Our results suggest that the tested automated FST system generates reliable data comparable to results obtained by trained observers.     

Behavioral and physiological mouse assays for anxiety: a survey in nine mouse strains

In order to find better and new treatments for anxiety in humans, a variety of paradigms are used to study anxiety-related processes in rodents. We studied mice in two different anxiety-related assays: the physiological stress-induced hyperthermia (SIH) paradigm and the behavioral light-dark exploration (LD) test. Eight inbred strains (129S6/SvEvTac, 129S1/SvImJ, A/J, BALB/cByJ, C3H/HeJ, C57BL/6J, DBA/2J, and FVB/NJ) and one outbred strain (CD1-ICR) were tested in both assays repeatedly. This study describes the first strain survey for the SIH paradigm. All strains showed an SIH response, but the magnitude of the response varied between lines. The inbred strain distribution pattern for the behavioral responses in the LD assay was not correlated with the SIH response. The lack of a significant correlation suggests that there is no genetic relation between such responses. Mice could be tested repeatedly in both assays without affecting the results. A new paradigm, in which both assays were combined, elucidated that behavioral responses were not altered by segments of the SIH paradigm. In contrast, exposure to the light-dark box instead of the home-cage showed a strain-dependent effect on the physiological response. We conclude that a combination of behavioral and physiological responses might lead to a better understanding in anxiety-related processes.     

Behavioural responses to novelty in two inbred mouse strains after intrahippocampal naloxone and morphine

Male C57BL/6 and DBA/2 mice were injected intrahippocampally with either naloxone (0.5 μg) or morphine (1.0 μg), or saline vehicle alone and, after 15 min, some 12 behavioural components carried out in a novel environment were recorded for 20 min. Naloxone reduced exploratory rearing responses, wall-leaning and object-sniffing in strain C57BL/6 and augmented these behaviours in strain DBA/2, while morphine depressed the scores in both. In conjunction with previously obtained evidence that the mouse hippocampus contains a genotype-dependent cholinergic mechanism which regulates responses to novelty, these findings support the hypothesis that hippocampal opioid peptides modulate the cholinergic control of exploration in mice, possibly indirectly through GABAergic pathways. In contrast, locomotor activity, defaecation and tail elevation remained practically unaffected by the two drugs, and grooming showed another kind of genotype-treatment interaction, that is to say, after morphine.     

Estrogen's effects on activity, anxiety, and fear in two mouse strains

Estrogen has effects on activity levels and emotional reactivity in both humans and rats. In a recent study conducted in ovariectomized (OVX) C57BL/6 (C57) mice we found that treatment with estradiol benzoate (EB) increased anxiety, fear learning, and running wheel activity relative to vehicle control (Veh). The present study was conducted to examine the stability of these findings across mouse strains (C57 and Swiss-Webster; SW), to get a better sense of the magnitude of the anxiety response by reducing baseline anxiety levels, and to discover if EB affects activity levels in a safe environment other than the home-cage running wheel. Mice of both strains treated with EB (s.c. implant, 25 microg in sesame oil, which enters the body over 5 weeks) were more anxious than Veh animals in the open field, elevated plus, and dark-light transition tests. SW animals were less anxious than C57 in the elevated plus. EB-treated animals of both strains were more active in the running wheel than Veh animals, and more active in the test of spontaneous activity in the home cage. EB-treatment also increased fear learning in a step-down avoidance task. EB appears to have a consistent but moderate effect in elevating anxiety and in increasing fear learning in two strains of mice. It is also involved in increasing activity in two different types of locomotion in the safer home cage. We conclude that these results of increased anxiety/fear and increased activity are suggestive of a general increase in arousal, with both sets of responses increasing the likelihood of reproductive behaviors occurring only when the environment predicts success.     

Behavioural phenotyping of mouse mutants.

Behavioural phenotyping of mouse mutants is not a goal in itself but serves to characterise the behavioural effects of naturally occurring or experimentally induced mutations. Genetically engineered mouse mutants are valuable tools to elucidate the genetic control of behaviour and the interaction between genetic and environmental factors. However, a prerequisite for their use is the ability to assess different elements of behaviour. To this end, a battery of tests, which should be flexible enough to meet the needs of a particular study, should be used to characterise the behavioural phenotype. Detailed and extensive information about the effects of gene mutations is crucial for model building and model evaluation. Model building is an iterative process, switching between experimental data and theory formation. In order to facilitate this process and to allow comparison of results within and between laboratories, the standardisation of breeding, housing, and testing conditions is essential. The development and standardisation of sensitive, valid behavioural tests which are suited to phenotype mouse mutants is both a responsibility and a challenge to investigators of mouse behaviour.     

Performance of different mouse strains in an object recognition task

In the present study, we tested the memory performance of different mouse strains (129/Sv, BALB/c, C57BL and Swiss) in an object recognition task. In this one-trial learning task, mice showed a good object memory performance when a 1-h delay was interposed between the first and second trial. However, when a 24-h delay was used, the mice did not discriminate between the novel and the familiar object in the second trial, indicating that the mice did not remember the object, which was presented in the first trial. Using a 4-h delay, the discrimination performance was at an intermediate level, suggesting a delay-dependent forgetting in this task. Although strain differences were found in the absolute level of exploration activity, no strain differences were found on the relative discrimination index (d2). The present data show that object memory can be assessed in mice and, in contrast to other memory tasks, appears to be less strain-dependent. The reliability of the discrimination measures is discussed.     

Behavioural changes after an acute stress: stressor and test types influences

Behavioural consequences of different acute stressors (30 min of restraint, 20 min of forced swim stress, 15 min of inescapable footshocks) applied at the beginning of the active period were assessed in using two behavioural tests: a 20 min light extinction test 24 h after the stressor exposure in order to explore the psychomotor ability and a 10 min open field session within the dark period 48 h after the stressor exposure to estimate the emotional status and the locomotor activity of the rat. Different behavioural responses were observed depending on the nature of the applied stressor. In the light extinction test, the footshock-stressed rats developed a very low activity independent on light conditions whereas the rats submitted to forced swim and restraint exhibited an activity level depending on the strain. Moreover, restrained rats had a higher transient activity than forced swim rats under light condition. In the open field test, none of the stressed rats did develop differences in behaviour. The efficacy of a 24 h recovery period on the behavioural response to an acute stressor exposure depends on the intensity of the applied stressor and the behavioural demands.     

Behavioural performance in three substrains of mouse strain 129

Recently, the possibility has been raised that the behavioural abnormalities seen in null-mutant mice might be determined by their genetic background rather than by loss of gene function, especially when the 129 mouse strain is used as supplier for embryonic stem (ES) cells. To examine this issue we tested three 129 mouse substrains (129/J, 129/Ola, 129/Sv-ter/+) and C57BL/6 (B6) in the Morris water maze, the open field, the plus maze and two tests assessing motor co-ordination. We identified only for the 129/J substrain substantial behavioural deficits. These mice are albinos and carry the pink-eyed dilution allele and differed in their basal anxiety level as assessed in the open-field test. They were severely impaired in spatial learning and memory (Morris water maze test), in the Porsolt swim test, which also measures learning and in motor co-ordination. However, the 129/J substrain has not been used as ES cell donor in null-mutant mice where behavioural abnormalities were observed. Instead, mice from 129/Ola and 129/Sv-ter/+ substrains have been commonly used as suppliers for ES cells. These performed normally in most of the tests, including Morris water maze test.     

Characterization of the profile of neurokinin-2 and neurotensin receptor antagonists in the mouse defense test battery

Defensive behaviors of lower mammals confronted with a predatory stimulus provide an appropriate laboratory model for investigating behavior relevant to human emotional disorders. The mouse defense test battery (MDTB) has been developed because it combines many of the aspects of defense. Briefly, it consists of five tests either associated with potential threat (contextual defense) or the actual presence of an approaching threat (a rat). These latter focus on changes in flight, risk assessment and defensive threat and attack behaviors. Investigations with anxiolytic compounds have shown that these defense reactions may be used to differentiate between several classes of anxiolytic drugs. Here we used the MDTB to compare the behavioral profile of the benzodiazepine diazepam with that of neuropeptide receptor antagonists which have been shown to be involved in the modulation of stress response, namely the NK₂ receptor antagonists, SR48968 (0.01–1 mg/kg) and SR144190 (1–10 mg/kg), and the NT₁ receptor antagonist, SR48692 (1–30 mg/kg). Results showed that all compounds decreased defensive threat/attack, but only diazepam and, to a lesser extent, SR48692 significantly modified risk assessment or flight. Further, none of the neuropeptide receptor antagonists modified contextual defense. Overall, the behavioral profile displayed by diazepam and these latter compounds in the MDTB are consistent with an anxiolytic-like action. However, our results suggest that, while NK₂ and NT₁ receptor antagonists may have limited efficacy on anxiety-related responses including cognitive aspects (i.e. risk assessment), they may have a potential against some forms of anxiety disorders which involve adaptative responses to extreme stress stimuli (e.g. direct confrontation with the threat stimulus).     

Behavioural and neural correlates of self-focused emotion regulation in social anxiety disorder

Background

In healthy individuals, voluntary modification of self-relevance has proven effective in regulating subjective emotional experience as well as physiologic responses evoked by emotive stimuli. As social anxiety disorder (SAD) is characterized by both altered emotional and self-related processing, we tested if emotion regulation through self-focused reappraisal is effective in individuals with SAD.

Methods

While undergoing 3 T functional magnetic resonance imaging, individuals with SAD and matched healthy controls either passively viewed neutral and aversive pictures or actively increased or decreased their negative emotional experience through the modification of self-relevance or personal distance to aversive pictures. Participants rated all pictures with regard to the intensity of elicited emotions and self-relatedness.

Results

We included 21 individuals with SAD and 23 controls in our study. Individuals with SAD reported significantly stronger emotional intensity across conditions and showed a nonsignificant tendency to judge pictures as more self-related than controls. Compared with controls, individuals with SAD showed an overactivation in bilateral temporoparietal regions and in the posterior midcingulate cortex during the passive viewing of aversive compared with neutral pictures. During instructed emotion regulation, activation patterns normalized and no significant group differences were detected.

Limitations

As no positive pictures were presented, results might be limited to the regulation of negative emotion.

Conclusion

During passive viewing of aversive images, individuals with SAD showed evidence of neural hyperreactivity that may be interpreted as increased bodily self-consciousness and heightened perspective-taking. During voluntary increase and decrease of negative emotional intensity, group differences disappeared, suggesting self-focused reappraisal as a successful emotion regulation strategy for individuals with SAD.     

Behavioural correlates of an altered balance between synaptic and extrasynaptic GABAAergic inhibition in a mouse model

GABAA receptors mediate fast phasic inhibitory postsynaptic potentials and participate in slower tonic extrasynaptic inhibition. Thy1alpha6 mice with ectopic forebrain expression of GABAA receptor alpha6 subunits exhibit increased extrasynaptic GABAA receptor-mediated background conductance and reduced synaptic GABAA receptor currents in hippocampal CA1 neurons [W. Wisden et al. (2002) Neuropharmacology 43, 530-549]. Here we demonstrate that isolated CA1 neurons of these mice showed furosemide-sensitivity of GABA-evoked currents, confirming the functional expression of alpha6 subunit. In addition, receptor autoradiography of the CA1 region of Thy1alpha6 brain sections revealed pharmacological features that are unique for alpha6betagamma2 and alpha6beta receptors. The existence of atypical alpha6beta receptors was confirmed after completely eliminating GABAA receptors containing gamma1, gamma2, gamma3 or delta subunits using serial immunoaffinity chromatography on subunit-specific GABAA receptor antibodies. Behaviourally, the Thy1alpha6 mice showed normal features with slightly enhanced startle reflex and struggle-escape behaviours. However, they were more sensitive to GABAA antagonists DMCM (shorter latency to writhing clonus) and picrotoxinin (shorter latency to generalized convulsions). Tiagabine, an antiepileptic GABA-uptake inhibitor that increases brain GABA levels, delayed picrotoxinin-induced convulsions at a low dose of 3.2 mg/kg in Thy1alpha6 mice, but not in control mice; however, the overall effect of higher tiagabine doses on the convulsion latency remained smaller in the Thy1alpha6 mice. Altered balance between extrasynaptic and synaptic receptors thus affects seizure sensitivity to GABAergic convulsants. Importantly, the increased extrasynaptic inhibition, even when facilitated in the presence of tiagabine, was not able fully to counteract enhanced seizure induction by GABAA antagonists.     

Differentiation and test anxiety in adolescents

The study tested several propositions about an important construct in Bowen's (Family Therapy in Clinical Practice, Aronson, New York, 1978; Family Evaluation, Norton, New York, 1988) theory of differentiation, using an Israeli sample of adolescents to examine relationships between differentiation of self, family differentiation, test anxiety, trait anxiety and cognitive performance. The main findings were that family differentiation (specifically, adolescents' relationships with their mothers) was negatively correlated with levels of test and trait anxiety and positively correlated with cognitive performance. All scales of differentiation of self, particularly emotional reactivity and I-position, were negatively correlated with both types of anxiety. Results suggest that differentiation is a meaningful construct for Israeli adolescents, and that less differentiated adolescents may be at risk for high levels of test anxiety and low levels of cognitive performance. Treatment of test-anxious adolescents therefore requires consideration of possible difficulties in individuating and differentiating from their families of origin.     

Evaluation of the elevated T-maze as an animal model of anxiety in the mouse

The elevated T-maze has been developed as an animal model of anxiety to generate both conditioned and unconditioned fears in the same rat. This study explores a version of the elevated T-maze fit for mice. Inhibitory (passive) avoidance- conditioned fear-is measured by recording the latency to leave the enclosed arm during three consecutive trials. One-way escape- unconditioned fear-is measured by recording the time to withdraw from open arms. The results showed that mice do not appear to acquire inhibitory avoidance in the standard T-maze, since their latencies to leave enclosed arm did not increase along trials. Nevertheless, the open arms seemed to be aversive for mice, because the latency to leave the enclosed arm after the first trial was lower in a T-maze with the three enclosed arms than in the standard elevated T-maze. In agreement, the exposure of mice to an elevated T-maze without shield, that reduces the perception of openness, increased significantly the latencies to leave the enclosed arm. However, the absence of the shield also increased the time taken to leave the open arms when compared to that recorded in standard T-maze. Systematic observation of behavioral items in the enclosed arm has shown that risk assessment behavior decreases along trials while freezing increases. In the open arms, freezing did not appear to influence the high latency to leave this compartment, since mice spend only about 8% of their time exhibiting this behavior. These results suggest that mice acquire inhibitory avoidance of the open arms by decreasing and increasing time in risk assessment and freezing, respectively, along three consecutive trials. However, one-way escape could not be characterized. Therefore, there are important differences between mice (present results) and rats (previously reported results) in the performance of behavioral tasks in the elevated T-maze.     

Behavioural abnormalities of the hyposulphataemic Nas1 knock-out mouse

We recently generated a sodium sulphate cotransporter knock-out mouse (Nas1-/-) which has increased urinary sulphate excretion and hyposulphataemia. To examine the consequences of disturbed sulphate homeostasis in the modulation of mouse behavioural characteristics, Nas1-/- mice were compared with Nas1+/- and Nas1+/+ littermates in a series of behavioural tests. The Nas1-/- mice displayed significantly (P < 0.001) decreased marble burying behaviour (4.33 +/- 0.82 buried) when compared to Nas1+/+ (7.86 +/- 0.44) and Nas1+/- (8.40 +/- 0.37) animals, suggesting that Nas1-/- mice may have decreased object-induced anxiety. The Nas1-/- mice also displayed decreased locomotor activity by moving less distance (1.53 +/- 0.27 m, P < 0.05) in an open-field test when compared to Nas1+/+ (2.31 +/- 0.24 m) and Nas1+/- (2.15 +/- 0.19 m) mice. The three genotypes displayed similar spatiotemporal and ethological behaviours in the elevated-plus maze and open-field test, with the exception of a decreased defecation frequency by the Nas1-/- mice (40% reduction, P < 0.01). There were no significant differences between Nas1-/- and Nas1+/+ mice in a rotarod performance test of motor coordination and in the forced swim test assessing (anti-)depressant-like behaviours. This is the first study to demonstrate behavioural abnormalities in the hyposulphataemic Nas1-/- mice.     

Behavioural characterization in rats using the elevated alley Suok test

Exploration of the long elevated alley (the rat Suok test) enables behavioural characterisation of anxiety, activity and neurological phenotypes in rats. Here we show that this new test is sensitive to different types of anxiety in rats, including drugs (pentylenetetrazole)-induced, light-induced and socially induced (encounter with an unfamiliar male) anxiety, as assessed by reduced Suok test horizontal, vertical, directed exploration and stops. High anxiety also leads to higher motor incoordination (as assessed by the number of falls and hind-paw slips), suggesting that this test may be used for combined profiling of anxiety, motor-vestibular anomalies and anxiety-induced motor incoordination in rats. This new behavioural paradigm may be widely used in neurobehavioural stress research, including modelling of stress-evoked states and pharmacological screening of psychotropic drugs.     

Behavioural and cognitive abnormalities in an imprinting centre deletion mouse model for Prader–Willi syndrome

The genes in the imprinted cluster on human chromosome 15q11–q13 are known to contribute to psychiatric conditions such as schizophrenia and autism. Major disruptions of this interval leading to a lack of paternal allele expression give rise to Prader–Willi syndrome (PWS), a neurodevelopmental disorder with core symptoms of a failure to thrive in infancy and, on emergence from infancy, learning disabilities and over‐eating. Individuals with PWS also display a number of behavioural problems and an increased incidence of neuropsychiatric abnormalities, which recent work indicates involve aspects of frontal dysfunction. To begin to examine the contribution of genes in this interval to relevant psychological and behavioural phenotypes, we exploited the imprinting centre (IC) deletion mouse model for PWS (PWS‐IC^+/?) and the five‐choice serial reaction time task (5‐CSRTT), which is primarily an assay of visuospatial attention and response control that is highly sensitive to frontal manipulations. Locomotor activity, open‐field behaviour and sensorimotor gating were also assessed. PWS‐IC^+/? mice displayed reduced locomotor activity, increased acoustic startle responses and decreased prepulse inhibition of startle responses. In the 5‐CSRTT, the PWS‐IC^+/? mice showed deficits in discriminative response accuracy, increased correct reaction times and increased omissions. Task manipulations confirmed that these differences were likely to be due to impaired attention. Our data recapitulate several aspects of the PWS clinical condition, including findings consistent with frontal abnormalities, and may indicate novel contributions of the imprinted genes found in 15q11–q13 to behavioural and cognitive function generally.