Ultrastructural features of GABAergic terminals labeled with the anti-GABA antibody in TTX-treated cerebella. (A) A GABAergic terminal contacts several spines with an asymmetrical phenotype; note the large size of such aberrant terminal. In the vicinity, an unlabeled PF terminal makes atypical asymmetric synapses with a spines. (Scale bar, 0.3 μm.) (B) Synapse between a GABAergic terminal and the dendritic shaft; note the presence of a double synapse with asymmetrical postsynaptic densities (PSDs) (arrowhead) close to a symmetrical region (arrow). The synaptic vesicles form a prominent cluster facing the symmetrical contact. (Scale bar, 0.15 μm.) (C) Asymmetrical GABAergic synapse characterized by a low vesicle density in the presynaptic region juxtaposed to the PSD. (Scale bar, 0.5 μm.) s, spine; PD, proximal dendrite; PF, parallel fiber.