Does triiodothyronine influence the morphogenesis of fetal mouse mesencephalic dopaminergic neurons cultured in chemically defined medium?

Serum-free cultures of mouse mesencephalic cells were used for studying the influence of triiodothyronine (T3) on the morphogenesis of dopaminergic neurons. Supplementation of culture medium with T3 (10(-9) M) did not modify the number, but increased the size of the perikarya without affecting the neurite density of mesencephalic dopamine (DA) neurons. Furthermore, T3 had no effect on the uptake of [3H]DA in these cultures. These findings, taken together with previous results obtained with hypothalamic cell cultures, show that T3 affects the morphogenesis of mesencephalic DA neurons in a different manner than that of hypothalamus and that the perikarya size on the one hand, and the neurite elongation on the other hand, seem to be independently regulated by T3.