The fine structure of staggerer cerebellum.

The cerebellar cortex of staggerer mice, ranging in age from 12 days to three months, was studied in the electron microscope. In general, the cerebellum showed a much delayed developmental pattern with regard to Purkinje cell spine formation. Spines did not appear on the soma until about 6 days after birth and appeared on the dendritic branchlets at only 23 days. Climbing fibers were present and they were in synaptic contact with both somatic and dendritic spines. By the third month, spines were only rarely obserbed and some of these were unattached to any presynaptic element.