Lithium chloride induces the expression of tyrosine hydroxylase in hNT neurons

In the present study, several doses of lithium chloride were tested for the ir ability to induce the expression of tyrosine hydroxylase (TH) in neurons derived from a human teratocarcinoma cell line (hNT) after 5 and 10 days i n vitro (DIV). Following immunocytochemical staining for tyrosine hydroxyla se, the percentage of TH-positive neurons was determined and morphometric a nalysis, including mean soma profile area and neuritic length, was performe d. hNT neurons responded to lithium treatment in a dose-dependent manner. I n 5 DIV, the most effective dose of lithium chloride (1.0 mM) increased the number of TH-positive neurons approximately sixfold. In addition, both TH- positive hNT neuron mean soma profile area and neurite length were signific antly larger than controls by 60 and 70%, respectively. Moreover, even afte r withdrawal of lithium chloride on day 5, the number of TH-positive neuron s in 10 DIV cultures remained significantly increased. These data suggest t hat hNT cells are indeed responsive to lithium exposure and may serve as a continual source of TH-expressing neurons in new therapeutic approaches to degenerative brain disease. (C) 1999 Academic Press.