Climbing fibers in mouse cerebellum co-cultured with inferior olive.

Cerebellar explants derived from neonatal mice were co-cultured with medulla containing inferior olive. The explants exhibited extracellular climbing fiber-like responses to electrical stimulation. On ultrastructural examination, many terminals with a high packing density of round, clear vesicles in a dark filamentous cytoplasm were present. Similar terminals, characteristic of climbing fibers, had not been identified in previous studies with cerebellar explants incorporating dorsal pons, but excluding medulla. The climbing fiber terminals formed appropriate synapses with Purkinje cell dendritic spines. The findings suggest that when climbing fibers are introduced into cerebellar cultures, accurate functional and morphological units are established.