FINE-STRUCTURE OF GABA-LABELED AXONAL ENDINGS IN THE INFERIOR COLLICULUS OF THE CAT - IMMUNOCYTOCHEMISTRY ON DEPLASTICIZED ULTRATHIN SECTIONS

Antisera to GABA conjugates and postembedding techniques were used to identify GABA-containing axonal endings at the electron microscopic level in the inferior colliculus. Over 90% of the GABA-labeled axonal endings had a similar morphology. They contained pleomorphic synaptic vesicles and made symmetrical synapses. The exceptional ending contained round vesicles and made symmetrical synaptic contacts or had pleomorphic vesicles with asymmetrical contacts. The majority of GABA-labeled axonal ending synapsed on dendrites; however, a few labeled axosomatic synapses were also found. Potential sources for these GABAergic synapses are neurons intrinsic to the inferior colliculus or from the dorsal nucleus of the lateral lemniscus. These findings suggest a basic similarity for most GABAergic endings in the inferior colliculus despite their possible origin from different cell types.