Comparison of brain serotoninergic systems in C57BL and BALBc mice during development.

Adult C57BL and BALBc mice will exhibit differences in behaviour and in their sleep patterns which may be correlated with monoamine content. In this study, we measured the endogenous levels of serotonin (5-HT), tryptophan (TRP), 5-hydroxyindole acetic acid (5-HIAA), noradrenaline (NA) and dopamine (DA) in the forebrain and hindbrain regions of these strains of mice from day 1 to 12 weeks of age. Using the micropunch technique and a radioenzymatic method, we also determined the endogenous 5-HT levels in the nuclei raphe dorsalis, centralis, magnus-pallidus and obscurus. During development, NA levels in the brain stem are higher in the C57BL than in the BALBc mice. From 5 weeks of age onwards, the levels of 5-HT, DA and NA in the forebrain are also higher in the C57BL mice. However, no differences in 5-Ht and DA content was found for the brain stems of these two strains. When the 5-HT levels in the different raphe nuclei were analyzed, the nucleus raphe dorsalis of the BALBc showed a higher 5-HT content.