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. 2023 Mar 29;10(1):136–154. doi: 10.1080/23328940.2023.2171671

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© 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. The terms on which this article has been published allow the posting of the Accepted Manuscript in a repository by the author(s) or with their consent.

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Figure 4. — The hypoperfusion response in the external oblique abdominal muscle to topical application of a TRPV1 agonist is abolished in rats desensitized with a low dose of i.p. RTX. (a) The upper curves in the left portion show that a rapid and profound decrease in blood flow in the external oblique abdominal muscle in response to topical administration of capsaicin (dose indicated) occurs in rats pretreated with vehicle (sham-desensitized) but not in rats pretreated with i.p. RTX (20 μg/kg) to induce localized abdominal TRPV1 desensitization. The lower curve shows that, in three randomly selected sham-desensitized rats, i.m. capsaicin caused no changes in the carotid blood pressure. Data plotted in the right portion of panel a show two responses of the same sham-desensitized and desensitized rats that were used in the perfusion experiment: 1) the number of writhes (during 10 min) induced by the i.p. administration of RTX (0.1 μg/kg) and 2) the number of eye-wiping movements (during 1 min) induced by the epicorneal application of capsaicin solution (10 μg/ml, 40 μl). Vehicle-pretreated rats had a strong writhing reflex, whereas this reflex was absent in rats pretreated with i.p. RTX, thus confirming successful desensitization of TRPV1 channels in the peritoneal cavity by the latter pretreatment. In contrast, there was no difference between sham-desensitized and RTX-desensitized rats in the eye-wiping test, indicating that extra-abdominal, at least corneal, TRPV1 channels were not affected by the i.p. RTX pretreatment. (b) Individual speckle photographs of the abdominal wall represent perfusion responses to capsaicin and vehicle of sham-desensitized and i.p. RTX-desensitized rats. For each rat and each treatment, a representative baseline (before-treatment) image is shown on the left, and a representative after-treatment (at 60 s after the i.m. administration of vehicle or capsaicin) is shown on the right.