Chemical coding and electrophysiology of enteric neurons expressing neurofilament 145 in guinea pig gastrointestinal tract

Electrophysiologic recording and indirect immunofluorescence were combined to study localization of the medium-sized neurofilament 145 (NF145) component of the cytoskeleton in morphologically identified neurons in the myenteric and submucosal plexuses of the guinea pig enteric nervous system. Neuronal localization of chemical markers, including calbindin DK28, calretinin, nitric oxide synthase, choline-acetyltransferase, neuropeptide Y, serotonin, neurokinin 1 receptor protein, and somatostatin, was integrated with electrophysiologic and morphologic results for a more complete assessment. NF145 immunoreactivity (-IR) was present in ganglion cells with Dogiel type I morphology in the myenteric plexus of the stomach and small and large intestine. NF145-IR was not found in myenteric ganglion cells with Dogiel type II morphology. NF145-IR was not present in any of the ganglion cells in the submucosal plexus. NF145 was expressed in nerve fibers in both myenteric and submucosal plexuses. The majority of these fibers were identified as sympathetic postganglionic axons based on their disappearance in organotypic culture and on their expression of tyrosine hydroxylase. The myenteric ganglion cells with NF145-IR had electrophysiologic properties of S-type enteric neurons. NF145-IR was found in neurons with vasoactive intestinal peptide, serotonin, nitric oxide synthase, somatostatin, and neurokinin 1 receptor but not with neuropeptide Y or calbindin. The results in general suggest that NF145 is localized to distinct subsets of myenteric motor neurons and interneurons. Absence of NF145 from ganglion cells in the submucosal plexus is an example of differences between myenteric and submucosal components of the enteric nervous system.