RECIPROCAL INFLUENCES OF NIGRAL CELLS AND STRIATAL PATCH NEURONS IN DISSOCIATED COCULTURES

Our previous work has shown that the functional efficacy of nigral tis sue transplants into dopamine (DA)-depleted rats is increased when emb ryonic striatal tissue is included (Costantini et al.: Exp Neurol 127: 219-231, 1994), To examine further the influence of striatal patch neu rons in this regard, we employed co-cultures of dissociated nigral and striatal cells taken from embryos at different ages. Striatal patch n eurons were labeled by in vivo bromodeoxyuridine (BrdU) on embryonic d ay (E)13 and E14. The percentage of striatal cells that were BrdU labe led was greater in E14 striatal cultures (51.0%) compared with E16 (33 .9%) and E20 (3.5%) striatal cultures at 1 day in vitro (DIV), The pro portion of surviving BrdU-labeled cells in striatal cultures decreased over time. The inclusion of E14 nigral cells attenuated this decline, Similarly, the number of dopaminergic [tyrosine hydroxylase (TH)-immu noreactive] neurons in pure nigral cultures decreased with time in vit ro (8.2% at 1 DIV to 3.5% at 12-15 DIV), The inclusion of E14 striatal tissue increased the number of TH-immunoreactive neurons at all time points, whereas E16 and E20 striatal tissue was somewhat less effectiv e. Thus, the survival of nigral DA neurons and striatal patch neurons in culture appears to be enhanced in the presence of the other. These reciprocal influences on neuronal survival mag be relevant to the in v ivo development of the nigrostriatal system as well as the enhanced fu nction of cells in co-transplants. (C) 1996 Wiley-Liss, Inc.