Neuropeptide-immunoreactive cells and fibers in the developing primate cerebellum

Using the avidin-biotin-peroxide immunohistochemical method, we studied the distributions of somatostatin (SOM)-, cholecystokinin-8 (CCK-8)- and substance P (SP)-like immunoreactivities in the cerebellum of macaque monkeys at embryonic day 120 (E120), E140, newborn, postnatal day 60 (P60) and adults. During the embryonic stages, there were many SOM-, CCK- and SP-immunoreactive structures in the external granular layer, Purkinje cell layer and white matter, SP-immunoreactive mossy fibers and their terminals were distributed in the granular layer and white matter. During these stages, there were SOM-immunoreactive Purkinje cells, Golgi cells and a few cells in the molecular layer, and CCK-immunoreactive Purkinje cells and cells in the molecular layer. At the newborn stage, all of the immunoreactivities in the external granular layer decreased and the number of immunoreactive fibers increased in the white matter. At P60 stage, SOM- and CCK-immunoreactive fibers were observed around Purkinje cells, which seem to be the fiber terminals of basket cells. Many SOM, CCK and SP fibers were distributed in the white matter. In the adult stage, we observed little neuropeptide-immunoreactivity in the cerebellum. The high concentration of the neuropeptide-immunoreactive fibers and cells in the earlier stages suggests that the neuropeptides may be involved in the development of the primate cerebellar cortex.