Chemical coding of neurons expressing δ- and κ-opioid receptor and type I vanilloid receptor immunoreactivities in the porcine ileum

Abstract

Opioid drugs have profound antidiarrheal and constipating actions in the intestinal tract and are effective in mitigating abdominal pain. Mediators of intestinal inflammation and allergy produce increased mucosal secretion, altered bowel motility and pain due to their ability to evoke enteric secretomotor reflexes through primary afferent neurons. In this study, the distribution of delta- and kappa-opioid receptor (DOR and KOR, respectively) immunoreactivities in chemically identified neurons of the porcine ileum was compared with that of the capsaicin-sensitive type 1 vanilloid receptor (VR1). DOR and VR1 immunoreactivities were observed to be highly localized in choline acetyltransferase (ChAT)- and calcitonin gene-related peptide (CGRP)-positive neurons and nerve fibers of the submucosal and myenteric plexuses and both receptors exhibited frequent colocalization. In the inner submucosal plexus, they also were colocalized in substance P (SP)-positive neurons. Neurons in the outer submucosal plexus expressed DOR immunoreactivity alone or in combination with VR1. KOR-immunoreactive neurons were found only in the myenteric plexus; these cells coexpressed immunoreactivity to ChAT, CGRP, vasoactive intestinal peptide (VIP) or nitric oxide synthase (NOS). In addition, some KOR-positive neurons coexpressed immunoreactivities to DOR and VR1. Based on their neurochemical coding, opioid and vanilloid receptor-immunoreactive neurons in the submucosal and myenteric plexuses may include primary afferents and constitute novel therapeutic targets for the palliation of painful intestinal inflammatory, hypersensitivity and dysmotility states.

Transient Receptor Potential Vanilloid Type 1 Channel (TRPV1) Immunolocalization in the Murine Enteric Nervous System Is Affected by the Targeted C-terminal Epitope of the Applied Antibody

“…However, the expression of TRPV1 in intrinsic enteric neurons is still controversial. Myenteric neurons were found to be TRPV1 immunoreactive in the guinea pig colon and ileum (Anavi-Goffer et al 2002;Anavi-Goffer and Coutts 2003), in the rat GI tract (Akiba et al 2001;Anavi-Goffer et al 2002;Anavi-Goffer and Coutts 2003), and in the porcine ileum (Kulkarni-Narla and Brown 2001; Poonyachoti et al 2002). Chan et al (2003) reported TRPV1 expression in submucosal and myenteric neurons in the human rectum.…”

HCl-activated neural and epithelial vanilloid receptors (TRPV1) in cat esophageal mucosa

“…Both substance P-and CGRP-containing neural cells have been demonstrated in the submucous plexus and a lamina propria subplexus of the intestine (10,25,31,49,50,53,56,59,62), but some controversy has been raised about the existence of neural cell bodies in the esophageal submucosa. Substance P-and CGRPcontaining neural cells, however, have been demonstrated in the human esophagus submucous plexus (55) and epithelium (54).…”

“…The remaining smooth muscle layer was cut into 2-mm circular muscle strips, which were mounted in separate 1-ml muscle chambers and used for electrical field stimulation (EFS), as previously described in detail (6). The esophageal mucosal tube consisted of epithelial cells, lamina propria, muscularis mucosae, and submucosa, including submucosal and lamina propria neurons (10,25,31,49,50,53,56,59,62), with the epithelial layer on the inside. The separation between mucosal sac and circular muscle strips was as close to the inner layer of the circular muscle as could be surgically achieved under the dissecting microscope; thus the sac included the submucosa, and it seems reasonable that whatever came out of the sac into the supernatant would directly affect the muscle layer.…”

Anandamide-Induced Depressor Effect in Spontaneously Hypertensive Rats

“…19 Preincubation of CGRP antiserum with its blocking peptides in 30-fold excess eliminated specific immunoreactivity. Omission of primary antibodies resulted in an absence of specific immunoreactivity.…”