TRPA1 is expressed on sensory neurons supplying the gastrointestinal (GI) tract and contributes to both normal mechanosensitivity and nociception [1, 2]. TRPA1 is also expressed in enterochromaffin (EC) cells leading to the release of serotonin [3], which has the potential to sensitize sensory nerve endings. Mast cell can also contribute to hypersensitivity [4]. We hypothesise therefore that there is a complex interplay between EC cells and mast cells, which serves to amplify TRPA1 signalling. Since sensory signaling from the GI tract diminishes with age [5] we further hypothesise that these modulating interactions are attenuated in aged mice. All experiments were performed on adult (3 month) or aged (24 month) male C57/BL6 mice in accordance with UK Home Office regulations. Afferent discharge was recorded from mesenteric nerves innervating a 2 cm segment of jejunum. The TRPA1 selective agonist allyl-isothiocyanate (AITC) was bath applied (1mM) at 50-minute interval and resulted in a reproducible afferent response. Treatment with cromolyn sodium (100 μM) or granisetron hydrochloride (30 μM) 15 minutes prior to the second application of AITC was used to determine contribution of mast cells and 5-HT3 receptors to AITC response. Data are expressed as mean afferent discharge frequency ± SEM and analysed using Students t-test. Quantitive RT-PCR was performed (in duplicate) using specific probes for mouse TRPA1 and 5-HT3 receptor on RNA isolated from DRGs and jejunum wall of aged and control mice. Data are expressed as fold change (aged vs. control) with > 2-fold change taken as significant. The increase in afferent discharge in response to AITC was significantly attenuated by cromolyn (72.5 ± 21.3 vs. 32.7 ± 9.8, P<0.05, paired t-test, N=6), suggesting that mast cells mediators amplify TRPA1 signalling. The response to AITC was also significantly inhibited by 30 μM granisetron (72.4 ± 15.4 vs. 21.3 ± 5.4, P<0.05, paired t-test, N=5) indicating a role for endogenous 5-HT, possible from EC cells. In aged mice, responses to AITC at a range of concentration were all significantly attenuated (100 μM: 19.9 ± 3.6 vs. 6.8 ± 3.4, P<0.05; 300 μM: 47.2 ± 10.2 vs. 15.7 ± 5.9, P<0.05; 1mM, 74.9 ± 7.3 vs. 28.8 ± 9.7, P<0.01; unpaired t-test, N=5). Expression of TRPA1 in the DRG and jejunum were not significantly different in young and aged mice (DRG, 1.58, N=5; jejunum, -1.42, N≥6), while 5-HT3B was significantly down regulated in jejunum (-2.11, N≥6) but not DRG (-1.06, N=4), which might contribute to the attenuation of TRPA1 signalling with ageing. This data suggests that there is an interplay between mast cells, EC cells and TRPA1 channels that might include both direct effects at the level of the sensory nerve terminal and amplification following the release of 5-HT and other inflammatory mediators. These mechanisms may be attenuated with ageing.