Specific stimulation of in vitro maturation of mesencephalic dopaminergic neurones by striatal membranes

We have previously established that dissociated mesencephalic dopaminergic (DA) neurones from embryonic mouse differentiate in primary cultures and that their development is enhanced when they are grown in the presence of their target cells from the striatum1–3. The capacity of individual DA neurones to take up and synthesize 3H-DA was increased in co-culture. This phenomenon does not depend on the presence of glial cells because it also occurred in serum-free conditions in which glial development was largely impaired4. Therefore, striatal target neurones favour the maturation of afferent DA neurones. Diffusible or membrane-bound factors could be involved in this process. To test one of these possibilities, we have now examined the in vitro development of embryonic mesencephalic DA neurones exposed to striatal membranes isolated from postnatal mice at various ages. 3H-DA uptake was used as an index of maturation of the DA neurones5. We show that striatal membranes from 2- and 3-week-old animals stimulate the development of DA neurones. The finding that this effect was not seen with membranes from 1-week-old or adult animals suggests that a developmentally regulated membrane-bound ‘factor’is probably involved. This factor seems to be specific for the DA neurones.