An analysis of GABAergic afferents to basket cell bodies in the cat's cerebellum.

An antibody to glutamic acid decarboxylase (GAD) was used to identify GABAergic terminals around the somata of basket cells in the cat's cerebellar cortex. Two sources for GAD immunoreactive terminals were identified based on size and cytological characteristics including the recurrent collaterals derived from Purkinje cells and the axons of stellate cells. The majority of the unlabeled terminals likely arise from parallel fibers. The present analysis indicates that GAD-positive terminals form 13% of the synaptic contacts on basket cells. The remaining 87% are unlabeled. Thus, GAD-positive terminals represent a small proportion of the synaptic input to basket cell bodies as compared to afferent endings that likely mediate excitation.