Immunocytochemical localization of choline acetyltransferase in the carotid body of the cat and rabbit.

The carotid body consists of afferent axon terminals in synaptic association with preneural type I cells and enveloping type II cells. The presence of acetylcholine (ACh) in this organ and its pharmacological actions are well established; however, its precise localization remains uncertain. In the present study, choline acetyltransferase was immunocytochemically localized to type I cells of the cat and rabbit. These data, combined with previous demonstrations of cholinergic receptor action, suggest that ACh may be involved in neurotransmitter coupling in the carotid body.