Effect of exposure to novelty on brain monoamines in C57BL/6 and DBA/2 mice

Male and female mice from two inbred strains, C57BL/6 (B6) and DBA/2 (D2), were exposed to a novel environment (vs. undisturbed control) for 10 min. Immediately after this treatment, the animals were sacrificed by cervical dislocation, and the brains were removed and dissected into ventral midbrain (VMB), caudate-putamen (CP), nucleus accumbens (NA), and medial prefrontal cortex (FC). Analyses of dopamine (DA) and its metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and serotonin (5-HT) and its metabolite, 5-hydroxyindole-3-acetic acid (5-HIAA) were made by high-performance liquid chromatography. Utilization of the parent amines was estimated by the ratios, DOPAC/DA, HVA/DA, and 5-HIAA/5-HT. Novelty increased DOPAC levels in NA of both strains of mice and in CP of D2 males; however, it did not induce significant changes in DA, or 5-HT levels or utilization of the latter. The results did, however, reveal large strain differences in DA and its metabolites. The data suggest that genetically based neurophysiological and neurochemical differences exist in dopaminergic and serotonergic systems in mice, and that the DA systems in NA may be more sensitive to novelty than other DA systems.