Tyrosine hydroxylase activity and its mRNA level in dopaminergic neurons of tenascin gene knockout mouse

We have recently demonstrated that some tenascin (TN) gene-knockout mice 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 frontal cortex, striatum, and hippocampus of TN-knockout mice which showed abnormal behavior was significantly decreased. Also, the TH mRNA level of the midbrain was decreased by 43% in these animals compared with values for wild-type mice. These results suggest that the low dopamine turnover rate in some areas of the brain of TN-knockout mice accompanied by motor defects is due, at least in part, to the reduction in TH activity caused by diminished TH mRNA expression, and that TN-knockout mice exhibit abnormal behaviors in the presence of low levels of TH-gene expression. (C) 1997 Academic Press.