Background and aims: Activation of corticotropin releasing factor 1 (CRF 1 ) receptors is involved in stress related responses and visceral pain, while activation of CRF 2 receptors dampens the endocrine and some behavioural stress responses. We hypothesised that CRF 2 receptor activation may influence visceral pain induced by colorectal distension (CRD) in conscious rats, and assessed the possible sites and mechanisms of action. Methods: Male Sprague-Dawley rats were exposed to CRDs (60 mm Hg, 10 minutes twice, with a 10 minute rest interval). Visceromotor responses (VMR) were measured by electromyography or visual observation. Spinal (L6-S1) extracellular signal regulated kinase 1/2 (ERK 1/2) activation following in vivo CRD and CRF 2 receptor gene expression in the T13-S1 dorsal root ganglia (DRG) and spinal cord were determined. Inferior splanchnic afferent (ISA) activity to CRD (0.4 ml, 20 seconds) was assessed by electrophysiological recording in an in vitro ISA nerve-inferior mesenteric artery (intra-arterial)-colorectal preparation. Results: In controls, VMR to the second CRD was mean 31 (SEM 4)% higher than that of the first (p,0.05). The selective CRF 2 agonist, human urocortin 2 (hUcn 2, at 10 and 20 mg/kg), injected intravenous after the first distension, prevented sensitisation and reduced the second response by 8 (1)% and 30 (5)% (p,0.05) compared with the first response, respectively. RT-PCR detected CRF 2 receptor gene expression in the DRG and spinal cord. CRD (60 mm Hg for 10 minutes) induced phosphorylation of ERK 1/2 in neurones of lumbosacral laminae I and IIo and the response was dampened by intravenous hUcn 2. CRD, in vitro, induced robust ISA spike activity that was dose dependently blunted by hUcn 2 (1-3 mg, intraarterially). The CRF 2 receptor antagonist, astressin 2 -B (200 mg/kg subcutaneously or 20 mg intraarterially) blocked the hUcn 2 inhibitory effects in vivo and in vitro. Conclusions: Peripheral injection of hUcn 2 blunts CRD induced visceral pain, colonic afferent, and spinal L6-S1 ERK 1/2 activity through CRF 2 receptor activation in rats.

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Background and aim-Epidermal growth factor (EGF) and transforming growth factor (TGF-), members of the EGF family of growth factors, protect rat gastric and colonic mucosa against injury. Having shown previously that exogenously applied EGF protects rat colonic mucosa against injury, the aim of the present study was to evaluate the endogenously expressed ligand mediating the protective eVect of EGF/TGF-in vivo. Methods-In an experimental model of trinitrobenzene sulphonic acid (TNBS)/ ethanol induced colitis in rats EGF and TGF-expression was evaluated using a ribonuclease protection assay, northern blot analysis, western blot analysis, and immunohistochemistry. Results-TGF-mRNA increased 3-4 times at 4-8 hours after induction of colitis and returned to control levels within 24 hours. TGF-immunoreactive protein with a molecular size of about 28 kDa representing TGF-precursors increased markedly after induction of colitis with a peak at 8-12 hours. No fully processed 5.6 kDa TGF-protein was detected in normal or inflamed colon tissue. Only a weak signal for EGF mRNA expression was detected in the rat colon and no EGF protein was observed by immunohistochemistry or western blot analysis. Conclusions-TGF-precursors are the main ligands for the EGF receptor in acute colitis. It is hypothesised that TGFprecursors convey the biological activity of endogenous TGF-peptides during mucosal defence and repair.

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