ROLE OF NEUROPEPTIDE-Y PROJECTION ON THE DEVELOPMENT OF SEROTONERGIC INNERVATION IN THE SUPRACHIASMATIC NUCLEUS OF THE RAT, SHOWN BY TRIPLEINTRAOCULAR GRAFTS

In our previous paper, the intraocular double grafts of fetal mesencep halic raphe and suprachiasmatic nucleus (SCN) demonstrated that the se rotonergic fibers from raphe tissue did not show a dense innervation o f SCN [28]. To examine the influence of NPY innervation from lateral g eniculate nucleus (LGN) on the development of serotonergic fibers in t he SCN, fetal mesencephalic raphe, SCN and LGN tissues were transplant ed together into the eye chamber of adult rat. 6 weeks after transplan tation, triple grafts were immunohistochemically examined. The SCN cel l cluster was recognized by vasoactive intestinal polypeptide (VIP)- a nd arginine vasopressin (AVP)-immunoreactive neurons and fibers. The S CN cell cluster also contained a large number of serotonin-immunoreact ive fibers from raphe tissue and a moderate number of neuropeptide Y ( NPY)-immunoreactive fibers from LGN tissue. The present results provid e information on possible NPY-serotonin interactions in the developing SCN.