Neuropeptide tyrosine-like immunoreactive nerve fibers in the carotid body chemoreceptor of rats.

Abundant NPY-immunoreactive nerve fibers were found throughout the parenchyma of the rat carotid body. They were in close proximity to smooth muscle cells and pericytes of small blood vessels intervening a narrow interstitial space of 80-150 nm. No immunoreactive nerve fibers were associated with chief or sustentacular cells. After removing the superior cervical ganglion, no immunoreactive nerve fibers were seen in the ipsilateral carotid body and the immunoreactive nerve fibers remained intact in the carotid body after cutting the ipsilateral superior cervical sympathetic trunk. The NPY-immunoreactive nerve fibers are therefore considered to be postganglionic sympathetic noradrenergic nerves.