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

Abstract

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.

High- and medium-molecular-weight neurofilament proteins define specific neuron types in the guinea-pig enteric nervous system

“…In marked contrast, two previous studies found that type II neurons in the guineapig enteric nervous system were not NF-immunoreactive (Costa et al 1996;Hu et al 2002), although other neurons with NF immunoreactivity were reported in both studies. The antibodies used in one of the studies were effective in revealing neurons containing NF-M and NF-H in the central nervous system (Costa et al 1996), whereas the other study involved the use of anti-NF-M antibodies to investigate myenteric neurons (Hu et al 2002). In the present work, we have utilised antibodies shown to be effective in other species in order to re-investigate the ability of anti-NF antibodies to label type II neurons in the guinea-pig small intestine.…”

“…Anti-NF antibodies are also ideal for the localisation of type II neurons in cattle (Balemba et al 1999), sheep (Mazzuoli et al 2007) and mice (Qu et al 2008). In marked contrast, two previous studies found that type II neurons in the guineapig enteric nervous system were not NF-immunoreactive (Costa et al 1996;Hu et al 2002), although other neurons with NF immunoreactivity were reported in both studies. The antibodies used in one of the studies were effective in revealing neurons containing NF-M and NF-H in the central nervous system (Costa et al 1996), whereas the other study involved the use of anti-NF-M antibodies to investigate myenteric neurons (Hu et al 2002).…”

“…For example, NF-H immunoreactivity is selectively expressed by the cell bodies of myelinated dorsal root afferent neurons and is present in only a minority of cell bodies of unmyelinated afferents (Lawson et al 1993). In the enteric nervous system, there is also differential staining of neurons revealed by anti-neurofilament antibodies (Barbiers et al 1995;Costa et al 1996;Brehmer et al 2002Brehmer et al , 2004Hu et al 2002;Sayegh and Ritter 2003;Ganns et al 2006). Type II neurons, which are readily distinguished by their large round or oval cell bodies and multiple axons (Brehmer et al 1999;Furness 2006) are characteristically revealed by anti-NF-H antibodies in the human and pig small intestine, where this is one of the best ways to demonstrate type II neurons (Brehmer et al 2002;Ganns et al 2006;Brehmer 2007;Wolf et al 2007).…”

Expression of the sodium channel Nav1.2 in chemically identified myenteric neurons in the guinea pig

“…Immunoreactivity for a specific medium weight form (NF145) was observed within numerous fibers coursing through internodal fiber tracts and within a small population of filamentous and Dogiel type I neurons in the myenteric plexus, similar to those previously described by Hu et al (2002). Immunoreactivity Fig.…”

“…At least three distinct classes of cholinergic descending interneurons are present in the ileum: one class is immunoreactive for serotonin (5-HT; Costa et al 1996), one class contains somatostatin (SOM; Song et al 1997), and one class contains vasoactive intestinal peptide (VIP; Steele et al 1991;. All 5-HT-immunoreactive and most SOM-immunoreactive myenteric neurons express the neurofilament subunit NF145 (Hu et al 2002). In our study, Na v 1.2 rarely co-localizes with NF145 in the ileum suggesting Na v 1.2 is not expressed by descending cholinergic interneurons containing 5-HT or by most containing SOM.…”