PLASTICITY OF TYROSINE-HYDROXYLASE GENE-EXPRESSION WITHIN BALB C AND C57BLACK/6 MOUSE LOCUS-COERULEUS/

The plasticity of tyrosine hydroxylase (TH) phenotype in the locus coe ruleus (LC) of two pure inbred strains of mice, Balb/C (C) and C57Blac k/6 (B6), was investigated at the molecular level by radioactive in si tu hybridization. The results demonstrated that in basal conditions, C mouse LC contains less TH-mRNA-expressing cells than B6. After RU 247 22-treatment, which induces long lasting TH gene expression in the LC, we previously reported an increase in TH-expressing cell number in C mouse LC only, equalizing TH phenotype between the two strains. Here, we demonstrate that strain specific plasticity of TH phenotype detecte d in spatially organized cells is associated with the regulation of TH -mRNA expression above a detectable level. These results suggest that interstrain differences and pharmacologically-induced phenotypic plast icity in TH phenotype may occur at the transcriptional level. (C) 1998 Published by Elsevier Science Ireland Ltd.