Distribution and chemical coding of corticotropin-releasing factor-immunoreactive neurons in the guinea pig enteric nervous system

Abstract

Immunofluorescence was used to study immunoreactivity (IR) for corticotropin releasing factor (CRF) in the guinea-pig enteric nervous system. CRF-IR was expressed in both the myenteric and submucosal plexuses of all regions of the large and small intestine and the myenteric plexus of the stomach. CRF-IR-nerve fibers were present in the myenteric and submucosal plexuses, in the circular muscle coat and surrounding submucosal arterioles. Most of the CRF-IR fibers persisted in the myenteric and submucosal plexuses after 7 days in organotypic culture. CRF-IR was not coexpressed with tyrosine hydroxylase-IR or calcitonin gene-related peptide-IR fibers. The proportions of CRF-IR cell bodies in the myenteric plexus increased progressively from the stomach (0.6%) to the distal colon (2.8%). Most of the CRF-IR myenteric neurons (95%) had uniaxonal morphology; the remainder had Dogiel type II multipolar morphology. CRF-IR cell bodies in the myenteric plexus of the ileum expressed IR for choline acetyltransferase (56.9%), substance P (55.0%), and nitric oxide synthase (37.9%). CRF-IR never co-localized with IR for calbindin, calretinin, neuropeptide Y, serotonin or somatostatin in the myenteric plexus. CRF-IR cell bodies were more abundant in the submucosal plexus (29.9-38.0%) than in the myenteric plexus. All CRF-IR neurons in submucosal ganglia expressed vasoactive intestinal peptide-IR and were likely to be secretomotor/vasodilator neurons. CRF-IR neurons did not express IR for the CRF 1 receptor. CRF 1 -IR was expressed in neuronal neighbors of those with CRF-IR. Collective evidence suggests that VIPergic secretomotor neurons might provide synaptic input to neighboring cholinergic neurons. Keywordsgastrointestinal tract; myenteric plexus; submucosal plexus; stress Clinical and experimental evidence suggests that stress is associated with the onset, symptom exacerbation and reactivation of gastrointestinal disorders, which include the irritable bowel syndrome, ulcerative colitis, Crohn's disease, gastroesophageal reflux disease and gastric ulcer (Duffy et al., 1991;Greene et al., 1994;Levenstein et al., 1994;Mayer, 2000;Peck and Wood, 2000;Wood et al., 2000;Wood, 2002;Drossman, 2004). Exposure of animals to stress causes erosions and ulceration in the gastric mucosa and inhibits gastric emptying coincident with stimulation of colonic motility, colonic transit, fecal pellet expulsion, mucosal electrolyte secretion and opening of the mucosal barrier to antigenic molecules (Fone et al., 1990; Taché, 1999;2001;Maillot et al., 2000 al., 20002;Million et al., 2002; Saunders et al., 2002a,b). Moreover, environmental stress factors initiate ulcerative colitis-like disease that is associated with colon cancer in primates Wood et al., 2000). The mechanistic details of these stressinduced gastrointestinal functional abnormalities are poorly understood. Nevertheless, the available evidence points to corticotropin releasing factor (CRF) signaling pathways in the brain and the gut as significant factors in the stress-evoked ...

Expression of corticotropin releasing factor (CRF) in the enteric nervous system of the jejunum of sheep

“…Sand et al (2011) also reported that the circular smooth muscle layer and mucous layer of the rat and guinea-pig small intestine contain moderate numbers of CRF-expressing nerve fi bres. However, in the above mentioned species sparse CRF-IR nerve fi bres were also detected in the longitudinal smooth muscle layer (Sand et al, 2011), as well as around submucosal arterioles (Liu et al, 2006;Sand et al, 2011), which is contradictory to our results. Double immunohistochemistry revealed no colocalization of TH with CRF in nerve fibres supplying the ovine jejunum which is in line with a previous study of Liu et al (2006), and indicates that no CRF-expressing nerve fibres are of extrinsic sympathetic origin.…”

“…In the ileum of the rat up to 50% of submucous neurons expressed CRF (Sand et al, 2011). Also in the duodenum, jejunum and ileum of the guinea-pig as many as 29.9%, 32.9% and 33.3% (respectively) of submucous neurons expressed CRF (Liu et al, 2006). In general, the distribution pattern of CRF-positive nerve fi bres of the ovine jejunum resembles those observed in the small intestine of other mammals.…”

“…In the rat ileum only a small number of CRF-IR (up to 5%) myenteric neurons were found (Sand et al, 2011), and in the guineapig small intestine only 2.0 CRF-positive neurons per myenteric ganglion (approx. 2%) were counted (Liu et al, 2006). We also revealed that in the ovine jejunum, a relatively small population of submucous neurons (approx.…”

“…In general, the distribution pattern of CRF-positive nerve fi bres of the ovine jejunum resembles those observed in the small intestine of other mammals. Similarly to sheep, in the rodent small intestine a rich network of CRF-expressing nerve fi bres was detected in both the myenteric and submucous plexuses (Wolter, 1984;la Fleur et al, 2005;Liu et al, 2006;Sand et al, 2011). Sand et al (2011) also reported that the circular smooth muscle layer and mucous layer of the rat and guinea-pig small intestine contain moderate numbers of CRF-expressing nerve fi bres.…”

“…In view of the previous fi ndings, it is apparent that the enteric nervous system (ENS) is of particular signifi cance in CRF signalling pathways aff ecting the gut. Th is is due to the fact that both CRF and CRF-receptors are present in enteric neurons (Chatzaki et al, 2004;Porcher et al, 2005;Liu et al, 2006;Sand et al, 2011) and peripheral infusion of CRF activates certain populations of CRF receptorbearing enteric neurons (Yuan et al, 2007).…”