Tachykininergic Axons in the Guinea Pig Carotid Body: Origin, Ultrastructure, and Coexistence with Other Peptides
Several peptides of the tachykinin family, substance P (SP), neurokinin A (NKA), and neuropeptide K are present in subpopulations of primary afferent neurons. SP-like immunoreactive (SP-LI) nerve fibers have been observed in the carotid body of many species (1–5) and it has been hypothesized that these axons represent the chemoreceptor afferents (4). This interpretation, however, generally, is not accepted (5), and, in fact, even the exact origin of SP-LI nerve fibres innervating the carotid body is unknown. Degeneration experiments revealed that, in the guinea pig, the bulk of SP-LI fibers is supplied via the carotid sinus nerve (CSN) to the carotid body (3). Extending this investigation, the present study was aimed to determine origin, ultrastructure, and coexisting peptides of these fibers.
KeywordsSucrose Paraformaldehyde Fluorescein FITC Calcitonin
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