BACKGROUND: Epineurial arterioles of the sciatic nerve are innervated by sensory nerves containing calcitonin gene-related peptide (CGRP). We postulated that treating these resistance vessels with capsaicin would cause the release of endogenous CGRP and vascular relaxation. METHODS: Videomicroscopy was used to examine the effect of capsaicin and neuropeptides on vascular reactivity of epineurial arterioles from control and streptozotocin-induced diabetic rats. Using immunohistochemistry, we examined expression of neuropeptide Y (NPY) and vanilloid receptor 1 in epineurial arterioles. RESULTS: Instead of relaxation, capsaicin was found to cause a concentration-dependent vasoconstriction in epineurial arterioles. The effect of capsaicin was transient, refractory, blocked by capsazepine and duplicated by resiniferatoxin. When examining potential candidates for the mediation of capsaicin-induced constriction, we found that vasopressin (VP), NPY, serotonin (5HT) and endothelin (ET), but not neurokinin A or substance P, caused a concentration-dependent vasoconstriction of epineurial arterioles. Epineurial arterioles express NPY and receptor antagonists to NPY significantly decreased capsaicin-induced vasoconstriction. In long-term diabetic rats, vasoconstriction to capsaicin was significantly attenuated. However, long-term diabetes did not impair vasoconstriction of epineurial arterioles to exogenous VP, NPY, 5HT or ET. Examining the expression of vanilloid receptor 1 in epineurial arterioles from control and long-term diabetic rats, we found that immunoreactivity for vanilloid receptor 1 was decreased by diabetes. CONCLUSIONS: These studies suggest that long-term diabetes causes vascular dysfunction in epineurial arterioles of the sciatic nerve that includes a decrease in capsaicin-induced vasoconstriction that is likely due to a decrease in the expression of vanilloid receptor 1.
BACKGROUND: Epineurial arterioles of the sciatic nerve are innervated by sensory nerves containing calcitonin gene-related peptide (CGRP). We postulated that treating these resistance vessels with capsaicin would cause the release of endogenous CGRP and vascular relaxation. METHODS: Videomicroscopy was used to examine the effect of capsaicin and neuropeptides on vascular reactivity of epineurial arterioles from control and streptozotocin-induced diabeticrats. Using immunohistochemistry, we examined expression of neuropeptide Y (NPY) and vanilloid receptor 1 in epineurial arterioles. RESULTS: Instead of relaxation, capsaicin was found to cause a concentration-dependent vasoconstriction in epineurial arterioles. The effect of capsaicin was transient, refractory, blocked by capsazepine and duplicated by resiniferatoxin. When examining potential candidates for the mediation of capsaicin-induced constriction, we found that vasopressin (VP), NPY, serotonin (5HT) and endothelin (ET), but not neurokinin A or substance P, caused a concentration-dependent vasoconstriction of epineurial arterioles. Epineurial arterioles express NPY and receptor antagonists to NPY significantly decreased capsaicin-induced vasoconstriction. In long-term diabeticrats, vasoconstriction to capsaicin was significantly attenuated. However, long-term diabetes did not impair vasoconstriction of epineurial arterioles to exogenous VP, NPY, 5HT or ET. Examining the expression of vanilloid receptor 1 in epineurial arterioles from control and long-term diabeticrats, we found that immunoreactivity for vanilloid receptor 1 was decreased by diabetes. CONCLUSIONS: These studies suggest that long-term diabetes causes vascular dysfunction in epineurial arterioles of the sciatic nerve that includes a decrease in capsaicin-induced vasoconstriction that is likely due to a decrease in the expression of vanilloid receptor 1.
Authors: Attila Tóth; Agnes Czikora; Eniko T Pásztor; Beatrix Dienes; Péter Bai; László Csernoch; Ibolya Rutkai; Viktória Csató; Ivetta S Mányiné; Róbert Pórszász; István Edes; Zoltán Papp; Judit Boczán Journal: J Histochem Cytochem Date: 2013-11-11 Impact factor: 2.479
Authors: Krisztina L Malisza; Cheryl Jones; Marco L H Gruwel; Derek Foreman; Paul Fernyhough; Nigel A Calcutt Journal: J Magn Reson Imaging Date: 2009-08 Impact factor: 4.813