INCREASED PROPORTION OF ACETYLCHOLINESTERASE-RICH ZONES AND IMPROVED MORPHOLOGICAL INTEGRATION IN HOST STRIATUM OF FETAL GRAFTS DERIVED FROM THE LATERAL BUT NOT THE MEDIAL GANGLIONIC EMINENCE

Fetal striatal grafts are found to have a modular organization reveale d by acetylcholinesterase (AChE) histochemistry. The AChE-rich zones r epresent the only portions of these grafts that are anatomically and f unctionally integrated into the host brain. In this study, the medial and lateral ganglionic eminences (MGEs and LGEs) were selectively diss ected from the basal telencephalon of embryonic-day-14 (E14) rat fetus es to compare their relative contributions to the AChE-rich fraction o f intrastriatal grafts. Separate cell suspensions prepared from either eminence were stereotaxically implanted into excitotoxically lesioned neostriatum of adult rats. Eight weeks after transplantation, grafts of the MGE were compared with those of the LGE with respect to the pro portion of AChE-rich zones, graft size, graft morphology, and afferent dopaminergic innervation as revealed by tyrosine hydroxylase (TH) imm unostaining. The mean AChE-rich fraction in LGE grafts (87% +/- 4%) wa s markedly greater than the AChE-rich fraction in MGE grafts (25% +/- 10%). The LGE grafts were also morphologically better incorporated int o the lesioned host striatum, partially reconstituting the striatal mo rphology. There was no statistically significant difference in graft s ize between the two groups. The AChE-rich LGE grafts were TH immunorea ctive, whereas the AChE-poor MGE grafts were not. We conclude that gra fts derived exclusively from the fetal LGE reconstitute the striatal m orphology and consist almost entirely of AChE-rich zones.