Dr. Scott will employ 1) correlative scanning-transmission electron microscopy; 2) immunocytochemistry; and, 3) microangiography to address three basic questions that deal with the underlying mechanisms of cellular interactions that occur between normal neuropeptide-producing fetal hypothalamic transplants and adult host rats of the Brattleboro strain with homozygous autosomal diabetes insipidus. The brains of host rats with viable indwelling fetal neurografts will be examined to determine the neuroanatomical patterns of neuronal and neurovascular integration that develop between the fetal hypothalamic transplants and surrounding host tissue and will confront the three following basic questions: 1) What are the underlying mechanisms of formation of vascular patterns and neurovascular interrelationships that develop between the host brain and the graft which serve to maintain the viability of extrinsic fetal neurografts? 2) What are the ultrastructural correlates underlying the mechanisms of synptogenesis and neuronal plasticity between the transplant and the host? 3) What are the fine structural correlates and major neuroanatomical routes for the delivery of centrally acting peptides? Data garnered from such experiments designs depicted below can serve as a model to establish a set of fine structural correlates that may apply to future neural transplantation.