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 ...