Distribution of corticotropin-releasing factor in the cerebellum and precerebellar nuclei of the cat.

The present study analyzes the distribution of corticotropin-releasing factor-immunoreactive (CRF-IR) fibers and neuronal cell bodies within the cerebellum and brainstem, respectively, of the cat. Within the cerebellum, CRF is present in climbing fibers, mossy fibers, and a population of varicose fibers which traverses the lower molecular layer. CRF-IR fibers are present throughout all lobules of the cat cerebellar cortex, though the density and immunostaining intensity of each fiber system vary. Bands of intensely immunoreactive climbing fibers are prominent within the vermis, intermediate cortex, and crus II. Bands of intensely immunoreactive mossy fiber terminals accompany the climbing fiber bands within the vermis. Collaterals of climbing and mossy fibers contribute to a beaded fiber plexus localized to the Purkinje cell layer. Varicose fibers containing CRF immunoreactivity are present in all deep cerebellar nuclei. CRF-IR neuronal cell bodies are prominent within several brainstem nuclei known to project to the cerebellum: all divisions of the inferior olivary complex, the lateral reticular nucleus, paramedian reticular nucleus, gigantocellular reticular nucleus, raphe nuclei, perihypoglossal complex, medial and inferior vestibular nuclei and cell groups f and x, locus ceruleus, and nucleus subceruleus. This study confirms and extends a previous study of CRF distribution within cerebellar afferent systems of the cat (Cummings et al.: J. Neurosci. 8:543-554, '88) and compares this distribution with previous descriptions in other species. The ubiquitous distribution of CRF throughout the cat cerebellum suggests a primary role for this peptide in signal transduction.