An improved procedure for integrated behavioral z-scoring illustrated with modified Hole Board behavior of male inbred laboratory mice.

BACKGROUND: Guilloux et al. introduced: integrated behavioral z-scoring, a method for behavioral phenotyping of mice. Using this method multiple ethological variables can be combined to show an overall description of a certain behavioral dimension or motivational system. However, a problem may occur when the control group used for the calculation has a standard deviation of zero or when no control group is present to act as a reference group. NEW METHOD: In order to solve these problems, an improved procedure is suggested: taking the pooled data as reference. For this purpose a behavioral study with male mice from three inbred strains was carried out. The integrated behavioral z-scoring methodology was applied, thereby taking five different reference group options. The outcome regarding statistical significance and practical importance was compared. RESULTS: Significant effects and effect sizes were influenced by the choice of the reference group. In some cases it was impossible to use a certain population and condition, because one or more behavioral variables in question had a standard deviation of zero. Based on the improved method, male mice from the three inbred strains differed regarding activity and anxiety. COMPARISON WITH EXISTING METHOD: Taking the method described by Guilloux et al. as basis, the present procedure improved the generalizability to all types of experimental designs in animal behavioral research. CONCLUSIONS: To solve the aforementioned problems and to avoid getting the diagnosis of data manipulation, the pooled data (combining the data from all experimental groups in a study) as reference option is recommended.

No role for vitamin D or a moderate fat diet in aging induced cognitive decline and emotional reactivity in C57BL/6 mice.

BACKGROUND: Epidemiological studies have shown associations between vitamin D, mental health and glucose homeostasis in the elderly. Causal evidence, however, is still lacking. OBJECTIVE: The objective of this study was to investigate the importance of vitamin D in the prevention of emotional disturbances and cognitive decline in aging C57BL/6 mice, with pre-diabetes type II as potential effect modifier. METHODS: Mice were exposed to one of four diets from 10 months till 24 months of age: low fat vitamin D adequate (LFD), LF vitamin D deficient (LF), moderate fat vitamin D adequate (MFD), and MF vitamin D deficient (MF). The MFD/MF diet was applied to induce a condition resembling pre-diabetes type II. Behavior was assessed twice in the same group of mice at 6-8 and at 22-23 months of age using the Open Field Test (OFT), Elevated Plus Maze (EPM), Object Recognition Test (ORT) and the Morris Water Maze (MWM). RESULTS: We successfully induced vitamin D deficiency in the LF/MF mice. Moreover, fasting glucose and fasting insulin levels were significantly higher in MFD/MF mice than in LFD/LF mice. A significant aging effect was observed for most behavioral parameters. A MF(D) diet was shown to delay or prevent the age-related increase in emotional reactivity in the EPM. No effect of vitamin D or vitamin D*fat on behavioral outcomes was measured. CONCLUSION: Aging significantly affected emotional reactivity and cognitive performance. Although other studies have shown effects of vitamin D on emotional reactivity and cognitive performance in mice, these findings could not be confirmed in aged C57BL/6 mice in this study.

The standardization-generalization dilemma: a way out.

Recently, a debate has emerged on the use and necessity of standardization in experimental testing using animal subjects. The difficulties encountered when trying to reconcile standardization and generalization largely underlie this debate. The more specific the testing procedures are, the less one can generalize to more naturalistic situations, including to human clinical populations. If the goal of a study is to generalize to a larger population, there may be a higher risk attached to false-positive than false-negative results; thus the balance sways toward generalization. Heterogenization of housing conditions and of genetic makeup of experimental animals has been suggested as a possible method to increase the generalizability of results. It is important to remain cognizant, however, of situations in which false negatives can be counterproductive or even dangerous, such as when the goal is to elucidate a physiological mechanism, when expected effect sizes are small, in toxicological studies and in drug safety testing. In such cases, experiments based on standardization may provide more useful information. We pose that it is essential that the goal of the specific experiment conducted is clearly defined and that the decision to balance between standardization and generalization must be made based on the specific needs to meet the intended goal. In this light, we discuss a multi-tiered approach to animal experimentation, in which standardization and generalizability are each given precedence during different phases of a project, depending upon the goal of the experiment.

Identifying emotional adaptation: behavioural habituation to novelty and immediate early gene expression in two inbred mouse strains.

Normal anxiety is an adaptive emotional response. However, when anxiety appears to lack adaptive value, it might be defined as pathological. Adaptation in animals can be assessed for example by changes in behavioural responses over time, i.e. habituation. We hypothesize that non-adaptive anxiety might be reflected by impaired habituation. To test our hypothesis, we repeatedly exposed male mice from two inbred strains to a novel environment, the modified hole board. BALB/cJ mice were found to be initially highly anxious, but subsequently habituated to the test environment. In contrast, 129P3/J mice initially showed less anxiety-related behaviour compared with the BALB/cJ mice but no habituation in anxiety-related behaviour was observed. Notably, anxiety-related behaviour even increased during the experimental period. Complementary, 129P3/J mice did not show habituation in other parameters such as locomotor and exploratory activity, whereas significant changes appeared in these behaviours in BALB/c mice. Finally, the expression of the immediate early gene c-fos differed between the two strains in distinct brain areas, known to regulate the integration of emotional and cognitive processes. These results suggest that 129P3/J mice might be a promising (neuro)-behavioural animal model for non-adaptive, i.e. pathological anxiety.

Methods for the behavioural phenotyping of mouse mutants. How to keep the overview.

The number of genetically engineered mice is constantly increasing. These animals play an important role in the development of useful models for human diseases. The Mutant Mice Behaviour-network, "MMB", was founded as a non-profit, international forum for presenting and discussing the behavioural phenotyping of these mice. The internet-based network will provide a standardised database that includes detailed descriptions of all parameters that might affect the behaviour of genetically engineered mice. This will lead to comprehensible and reproducible tests and, in the future, might lead to an interdisciplinary consensus on methods for mouse behavioural phenotyping.

The Mutant Mouse Behaviour network, a medium to present and discuss methods for the behavioural phenotyping.

The nonprofit international Mutant Mouse Behaviour network "MMB" was founded within the framework of the conference "Behavioural Phenotyping of Mouse Mutants", February 2000, held in Cologne, Germany. It intends to be a forum for presenting and discussing all topics dealing with the behavioural phenotyping of mice. The major aim of the MMB is to support the interdisciplinary finding of a consensus on the methods and techniques used for behavioural phenotyping of mouse mutants. That means that scientist involved in the development of mouse models have to consent to the fact that a consideration of all the parameters that might affect the behaviour is necessary. Finding and establishing a consensus is a fluent process based on a continuous exchange of information. The network will provide a standardised database that includes detailed descriptions of test methods and of the relevant background parameters that might influence the behaviour of mice. Information will range from detailed descriptions of test methods, specifications of the equipment used, housing conditions, and specifications of the animals used according to the international nomenclature. The detailed descriptions will help in making behavioural tests and their results comprehensible and reproducible. A mailing list has been established to provide a platform for the continuous exchange of information between the network members. It will be a forum for discussing all topics related to behavioural phenotyping (see above). Scientists from all research areas involved are free to provide detailed information about their experimental work, and will, in return, get a quick response to their questions. Furthermore, the mailing list will be a useful medium to determine which information should be incorporated.