Autoradiography of mossy fiber terminals in the fastigial nucleus of the cat.
Terminal boutons of mossy fiber collaterals in the fastigial nucleus originating from the nucleus reticularis tegmenti pontis, the bulbar reticular formation, and the medial vestibular nucleus were studied with high-resolution autoradiography in order to examine their ultrastructural features and synaptic relations. Labeled mossy fiber boutons ranged in size from 0.5 to 5 micron in diameter, and they all contained clear and spherical vesicles in an electron-lucent matrix, mitochondria, and some fine tubular elements. These boutons form asymmetric synapses with dendritic profiles of different sizes. No evidence was found for mossy fiber termination on the soma of fastigial neurons. Two types of mossy fiber terminals were distinguished on the basis of the aggregation of synaptic vesicles: one type with clustered vesicles and one type with densely packed vesicles, occurring in equal number from all sources. Furthermore, the applicability of the congruity hypothesis is confirmed for the general identification of terminals.
D000344:Afferent Pathways / Q000033:anatomy & histology; D000818:Animals; D002415:Cats; D002529:Cerebellar Nuclei / Q000033:anatomy & histology*; D008526:Medulla Oblongata / Q000033:anatomy & histology*; D008854:Microscopy, Electron; D011149:Pons / Q000033:anatomy & histology*; D012154:Reticular Formation / Q000033:anatomy & histology*; D013569:Synapses / Q000648:ultrastructure; D014726:Vestibular Nuclei / Q000033:anatomy & histology*