Paraneuronal grafts in unilateral 6-hydroxydopamine-lesioned rats: Morphological aspects of adrenal chromaffin and carotid body glomus cell implants

Implants of both chromaffin and glomus cells reverse amphetamine-induced rotational behavior and appear viable in the unilateral 6-hydroxydopamine (6-OHDA) rodent model. This chapter describes the potential of several alternative sources of donor tissue for neural transplantation, and emphasizes upon two members of the sympathoadrenal cell lineage, the adrenal chromaffin and carotid body glomus cells, as implants in the unilateral 6-hydroxydopamine (6-OHDA) rodent model. The particular focus of the present study is on the fine structure of these paraneuronal grafts 30 days post-implantation into the denervated striatum. Once implanted, the chromaffin cells demonstrate a plasticity of their dense-core vesicles, with the average diameter decreasing in size when compared to normal adrenal medullary cells. However, the study raises some important questions that need to be addressed, such as (1) will these paraneuronal cells survive and continue to exert positive behavioral effects in long-term experiments, and (2) what is the critical mass of implanted tissue needed to achieve functional recovery, and where in the brain are the optimal sites for ransplantation of these cells. The chapter indicates that answers to these questions are essential for designing rationale clinical approaches for the treatment of parkinsonism, and to encourage the acceleration of transplantation research in appropriate animal models.