Journal
JOURNAL OF PHYSIOLOGY-LONDON
Volume 552, Issue 2, Pages 589-601Publisher
CAMBRIDGE UNIV PRESS
DOI: 10.1113/jphysiol.2003.049387
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Funding
- NIDDK NIH HHS [R01 DK057840, R01 DK043207, R56 DK043207, DK57840, DK43207] Funding Source: Medline
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Proteinase-activated receptor 2 (PAR2) is a receptor for mast cell tryptase and trypsins and might participate in brain-gut communication. However, evidence that PAR2 activation can lead to afferent impulse generation is lacking. To address this issue, we examined the sensitivity of jejunal afferent nerves to a hexapeptide agonist of PAR2, SLIGRL-NH2, and the modulation of the resulting response to treatment with drugs and vagotomy. Multiunit recordings of jejunal afferent activity were made using extracellular recording techniques in anaesthetised male rats, SLIGRL-NH2, (0.001-1 mg kg(-1), I.V.) increased jejunal afferent firing and intrajejunal pressure. The reverse peptide sequence (I mg kg(-1), I.V.), which does not stimulate PAR2, was inactive. Naproxen (10 mg kg(-1), I.V.), but not a cocktail of omega-conotoxins GVIA and SVIB (each at 25 mug kg(-1), I.V.), curtailed both the afferent response and the intrajejunal pressure rise elicited by the PAR2 agonist. Although neither treatment modulated the peak magnitude of the afferent firing, they each altered the intestinal motor response, unmasking an initial inhibitory component. Nifedipine (I mg kg(-1), I.V.) reduced the peak magnitude of the afferent nerve discharge and abolished the initial rise in intrajejunal pressure produced by SLIGRL-NH2. Vagotomy did not significantly influence the magnitude of the afferent response to the PAR2 agonist, which involves a contribution from capsaicin-sensitive fibres. In conclusion, intravenous administration of SLIGRL-NH2 evokes complex activation of predominantly spinally projecting extrinsic intestinal afferent nerves, an effect that involves both direct and indirect mechanisms.
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