Allyl isothiocyanate, an activator of TRPA1, increases gastric mucosal blood flow through calcitonin gene-related peptide and adrenomedullin in anesthetized rats

Allyl isothiocyanate (AITC) activates transient receptor potential ankyrin 1 (TRPA1) channel, which is involved in the control of intestinal mucosal blood flow. However, the mechanism underlying the increased gastric mucosal blood flow (GMBF) in response to AITC remains unknown. We examined the effect of AITC on GMBF in the ex vivo stomachs of normal and sensory deafferented rats using a laser Doppler flowmeter. Mucosal application of AITC increased GMBF in a concentration-dependent manner. Repeated AITC exposure resulted in a marked desensitization. The increased GMBF response induced by AITC was entirely blocked by co-application of TRPA1 channel blockers HC-030031 or AP-18. Increased GMBF in response to AITC was significantly attenuated by chemical deafferentation following systemic capsaicin injections (total dose: 100 mg/kg). In contrast, increased GMBF responses to capsaicin, a transient receptor potential vanilloid 1 (TRPV1) activator, were completely abolished by chemical deafferentation. The increased GMBF response to AITC was markedly inhibited by BIBN 4096, a calcitonin gene-related peptide receptor (CGRP) antagonist, or AGP-8412, an adrenomedullin receptor antagonist. These results suggest that AITC-stimulated TRPA1 activation results in the increased GMBF through the release of CGRP and adrenomedullin.