TROPHIC AND TROPIC EFFECTS OF STRIATAL ASTROCYTES ON COGRAFTED MESENCEPHALIC DOPAMINE NEURONS AND THEIR AXONS

Astrocytes from the ventral mesencephalon and from the striatum respec tively promote the dendritic and axonal arborization of dopamine (DA) neurons in vitro., To test this response in vivo, astrocytes in primar y cultures from the neonatal cerebral cortex, ventral mesencephalon, o r striatum were coimplanted with fetal ventral mesencephalic tissue in to the intact or DA-denervated striatum of adult rats and these cograf ts examined after 3-6 months by tyrosine hydroxylase (TH) immunohistoc hemistry (intact recipients) or after 5-6 months by in vitro [H-3]DA-u ptake autoradiography (DA-denervated recipients), In contrast with sin gle ventral mesencephalic grafts, all types of cograft displayed a rat her uniform distribution of TH-immunoreactive perikarya, The average s ize of TH-immunoreactive cell bodies was not significantly different i n cografts containing cortical or mesencephalic astrocytes and in sing le ventral mesencephalic grafts, but it was significantly larger in co grafts containing striatal astrocytes, Nevertheless, the number of [H- 3]DA-labeled terminals in the DA-lesioned host striatum was clearly sm aller with cografts of striatal astrocytes than with single mesencepha lic grafts or with cografts containing cortical astrocytes, On the oth er hand, cografts of striatal astrocytes contained much higher numbers of [H-3]DA-labeled terminals than the other types of graft or cograft . Thus, while cografted astrocytes in general influence the distributi on of DA neurons within the graft, astrocytes from the neonatal striat um have a trophic effect on DA perikarya and a tropic effect on DA axo ns, keeping the latter within the graft, (C) 1998 Wiley-Liss, Inc.