Tyrosine hydroxylase mRNA in the dopaminergic neurons of young adult and aged mice by in situ hybridization.

Tyrosine hydroxylase (TH) mRNA in the dopaminergic neurons of the substantia nigra (SN) and the ventral tegmental area (VTA) in young adult and aged mice was detected and quantitated using in situ hybridization. Using 3H-labeled antisense RNA complementary to TH mRNA, these studies demonstrate the presence of TH mRNA in dopaminergic neurons of the SN and the VTA. Alternate sections stained immunocytochemically using TH-specific antiserum demonstrated that the neurons containing TH mRNA also contained TH protein. Quantitative analysis of the number of silver grains present over the dopaminergic neurons of the SN and VTA revealed no statistically significant difference between the two age groups. The results suggest that TH gene expression in dopaminergic neurons of the SN and VTA is not different in young adult and aged mice.