Electron microscopic identification of cerebellar nucleo-cortical mossy terminals in the rat

Intact mossy terminals observed in the granular layer of rat cerebella, two weeks after complete transection of all cerebellar peduncles, were identified as the endings of the intracerebellar nucleo-cortical afferents. A quantitative study of synaptic vesicle size spectra revealed clear differences between nucleo-cortical and true extracerebellar mossy afferents. These differences suggest that the nucleo-cortical afferents are recurrent collaterals of the projective nucleofugal fibers.