Behavior and brain neurotransmitters: correlations in different strains of mice

Correlations of behavioral patterns in a social setting with catecholamines, serotonin, and several metabolites and precursors in three brain regions were examined in the DeFries H2, C1, and L1 strains of mice. In Experiment I, behavioral observations were recorded for two 15-min sessions in same-sex, same-strain pairs at about 65 days of age. In Experiment II, sex and strain groups were subdivided into 4% and 24% protein diet groups about 1 week before a second set of behavioral observations at about 120 days of age. Brain tissue content of neurotransmitters, precursors, and metabolites was determined by high-performance liquid chromatography after the second set of observations. Significant multivariate strain differences were shown for behavioral variables (both experiments) as well as concentrations of various neurochemicals. Strain H2 showed relatively high levels of locomotion, while rearing and social investigation were high in strain C1 and self-grooming in strain L1. Significant neurochemical differences were found in the following sets of variables: dopamine variables in the cortex, norepinephrine variables and serotonin variables in the combined diencephalon and midbrain, and norepinephrine and serotonin variables in the hindbrain. Effects of diet were found only on serotonin and tryptophan in the subcortical regions. Significant multivariate correlation with the behavioral variables was demonstrated for the catecholamines but not for serotonin. The results suggest that these strain differences in behavior may be mediated by catecholamine systems.