Effect of striatal cells on in vitro maturation of mesencephalic dopaminergic neurones grown in serum-free conditions

Abstract

It is well documented that target cells can regulate the morphological and biochemical development of peripheral afferent neurones^1,2, but little is known about the existence of such regulatory mechanisms in the central nervous system. We therefore investigated previously the influence of striatal target cells on the maturation in vitro of nigrostriatal dopaminergic neurones, which survive in culture for more than 5 weeks, develop dense arborizations and both take up ³H-dopamine(DA) by a high-affinity specific process and synthesize ³H-DA from ³H-tyrosine³. Furthermore, depolarization by potassium or veratridine stimulates the release of DA through a calcium-dependent mechanism and tetrodotoxin prevents the veratridine-evoked release of the transmitter⁴. Both the number of ³H-DA uptake sites and the capacity for ³H-DA synthesis were at least doubled when the neurones were cultured with target cells from the striatum³. To determine whether glial cells which proliferate in serum-complemented medium are partly responsible for the maturation of dopaminergic neurones and/or for the effect of striatal cells, we have now repeated the experiment using serum-free medium in which virtually pure neuronal populations can be obtained^5–7. The reduction in the number of glia did not affect either the maturation of dopaminergic cells alone, or the effect of striatal cells. Autoradiographic analysis of the number of dopaminergic cells strongly suggests that the stimulatory effect is related to increased capacities of ³H-DA uptake and synthesis per dopaminergic neurone.