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Dai Ogino, Shun Watanabe, Yusuke Ohta, Kota Fujiwara, Takeshi Yoshitomi; Effects of Calcitonin Gene Related Peptide on Bovine Trabecular Meshwork and Ciliary Muscle. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3554.
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Calcitonin Gene Related Peptide (CGRP) localizes to trabecular meshwork (TM) and ciliary muscle (CM). Intracameral injection of CGRP increases the outflow facility in cat. Substance P (SP) co-localizes with CGRP in many nerve fibers. The purpose of this study is to investigate the effect of CGRP and SP on the contractility of bovine TM and CM by measurement of isometric tension recording methods.
Bovine eyes were obtained from a local slaughterhouse. A small piece of specimens were carefully dissected from an excised ciliary muscle bundle and trabecular meshwork. The preparation was vertically mounted in a small organ bath through which solution flowed at a constant rate. The tension was isometrically recorded using a U-gauge transducer.
CGRP (30 nM) relaxed both bovine TM and CM which were precontracted by carbachol (2 μM) , while SP (1 μM) had no effect. Pretreatment with CGRP 8-37 (100 nM), selective competitive antagonist at CGRP receptors, significantly attenuated the relaxation response on TM and CM.
Various agents may modulate the contractility of trabecular meshwork and may be actively involved in the regulation of intraocular pressure. We revealed that CGRP have a relaxing effect on contracted bovine TM and CM. These results indicate that CGRP binding sites are in bovine TM and CM. CGRP may have an important role to control aqueous humor dynamics.
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