The role of calcium in endotoxin-induced release of calcitonin gene-related peptide (CGRP) from rat spinal cord.

In the present study, the role of calcium in endotoxin-induced CGRP release was studied. 2.5–50 CLg/mL endotoxin and 1–10 mmol/L caffeine caused concentration-dependent increase of CGRP release from rat spinal cordin vitro. However, no additive effect could be found when caffeine and endotoxin were concomitantly incubated. By using capsaicin, Ca2+-free medium, Omega-Conotoxin, nifedipine, W-7, ryanodine, MgCl2, Tris-ATP, ruthenium red, the results indicate that the release of CGRP evoked by endotoxin from the sensory fibers of rat spinal cord is dependent on extracellular calcium. After entering into the cell through the N-type calcium channel, calcium binds to calmodulin, and triggers calcium release from intracellular calcium store by activating the caffeine-sensitive but ryan-odine-insensitive mechanism.