DISTRIBUTION OF TYROSINE HYDROXYLASE-IMMUNOREACTIVE AFFERENTS TO THE CEREBELLUM DIFFERS BETWEEN SPECIES

indirect antibody peroxidase-antiperoxidase technique was used to dete rmine the laminar and lobular distribution of catecholaminergic affere nts in the adult mouse, opossum, and cat cerebellum. A monoclonal anti body to tyrosine hydroxylase (TH) revealed a plexus of thin varicose f ibers that exhibited a different density and distribution pattern for each species. In the cat, TH-immunoreactive fibers were sparsely distr ibuted to all laminae, lobules, and nuclei of the cat cerebellum excep t for an area of elevated density in the ventral folia of lobules V an d VI. In the opossum, TH-positive fibers were uniformly and densely di stributed in the granule and Purkinje cell layers; they were more abun dant in vermal lobules V-VI than in more anterior and posterior lobule s, particularly I and X. Numerous TH-immunoreactive fibers were found in all four cerebellar nuclei of the opossum. In the mouse, TH-positiv e fibers formed a dense plexus within all cerebellar lobules, laminae, and nuclei. The mouse also exhibited numerous TH-immunoreactive Purki nje cells that were localized predominantly within vermal lobules VI-X , the paraflocculus, and flocculus. In addition to the interspecies di fferences in the distribution of catecholaminergic fibers within the c erebellum, comparison of this plexus to that previously described for serotonin in these species reveals that the relative densities and dis tribution patterns of catecholaminergic and serotoninergic fibers also vary between species. It is thus hypothesized that in each species a given monoamine has a unique net effect on cerebellar output that is d etermined by its effects on different neuronal populations within the cerebellum. (C) 1997 Wiley-Liss, Inc.