TYROSINE-HYDROXYLASE ACTIVITY AND ITS MESSENGER-RNA LEVEL IN DOPAMINERGIC-NEURONS OF TENASCIN GENE KNOCKOUT MOUSE

We have recently demonstrated that some tenascin (TN) gene-knockout mi ce display abnormal behaviors, and that these abnormal behaviors stem from a low level of dopamine transmission in the brain. In the present study, we elucidated that tyrosine hydroxylase (TH) activity in the f rontal cortex, striatum, and hippocampus of TN-knockout mice which sho wed abnormal behavior was significantly decreased. Also, the TH mRNA l evel of the midbrain was decreased by 43% in these animals compared wi th values for wild-type mice. These results suggest that the low dopam ine turnover rate in some areas of the brain of TN-knockout mice accom panied by motor defects is due, at least in part, to the reduction in TH activity caused by diminished TH mRNA expression, and that TN-knock out mice exhibit abnormal behaviors in the presence of low levels of T H-gene expression. (C) 1997 Academic Press.