Comparing different inbred strains is a common neurogenetic approach to identify gene-dependent behavioral as well as neural variables. Such comparisons require detailed knowledge about the behavioral and physiological characteristics of such strains. Here, we present data which address the research methodology with which (a) differences between mouse strains can be detected and quantified at the behavioral level, and (b) can be related to neural variables. These data are based on a complex and integrative analysis of male and female adult mice from the C57Bl/6 and Balb/c strain. Behavioral testing included open-field and plus-maze behaviour, inhibitory avoidance, and several tests of motor coordination (i.e. rotarod, grip- and pole-test). Furthermore, lesions with MPTP were performed, a neurotoxin which is used to destroy the nigrostriatal pathway and which serves as an experimental model for Parkinson’s disease. In addition to the behavioral analyses, the contents of dopamine, norepinephrine, and serotonin as well as their metabolites were determined in the neostriatum and ventral striatum using a post mortem analysis with HPLC.

Our analyses provide a number of indications for strain- and sex-dependent differences. Behaviorally, C57Bl/6 mice were more active in the open-field than Balb/c; C57Bl/6 females showed the highest levels of activity, but also the strongest habituation. Further quantitative and qualitative behavioral strain differences were observed in plus-maze behaviour, inhibitory avoidance, rotarod, and the grip- and pole-test. The occurrence of such strain differences were found to be affected by environmental factors, such as the lighting conditions. The behavioral differences were paralleled by neurochemical differences, especially of dopamine activity in the neostriatum. Treatment with MPTP proved to reduce locomotor activity and movement coordination in both strains, leading to different patterns of recovery. Here, open-field behavior and the pole-test proved to serve as sensitive indicators. Neurochemically, MPTP caused depletions of neostriatal dopamine levels in both strains and sexes; this effect was more pronounced in C57Bl/6 mice.

Our findings confirm the critical role of dopamine for locomotor and exploratory behavior. Regarding behavioral analysis, they indicate the need to carefully control environmental variables, such as light. Furthermore, they provide an extended set of data on two common inbred strains. These informations can, for instance, be used to choose appropriate strains, behavioral measurements and testing conditions in future neurogenetic models.