Experimental Study On Zinc Inhibiting Calcitonin Gene Related Peptide Expression And Influencing Neuropathic Pain

ObjectiveTo observe the effect of zinc on the expression of calcitonin gene relatedpeptide(CGRP) expression in capsaicin induced neuropathic pain model micespinal cord, cultured neuron and the animal ethology.MethodsIn the animal experiments,48C57/BL6mice were randomly divided intofour groups and neuropathic pain model was built by plantar injection ofcapsaicin (0.5%,5μl). In the control group, mice were fed by normal zinc food(zinc30mg/kg/d) for2weeks and then injected solvent (Tween80, alcohol andsaline mixture). In normal diet group, mice were fed by normal zinc food (zinc30mg/kg/d) for2weeks and then injected capsaicin. In low zinc diet group,mice were fed by low zinc food (zinc0.85mg/kg/d) for2weeks, then injectedcapsaicin. In high zinc diet group, mice were fed by zinc chloride solution(227mg/L/d) for2weeks, then injected capsaicin. Animal ethology behaviordetection, immunohistochemistry, Western blot and image analysis techniqueswere used to detect the effect of zinc on the animal ethology and the CGRPexpression in spinal cord. In vitro, primary cultured rat cortical neurons wererandomly divided into four groups. Control group: cultured by medium for24h,then add the solvent; normal group: cultured by the medium for24h, then add capsaicin (200μmol.L-1); low zinc culture group: cultured by clioquinol (5μmol.L-1)for24h, then add capsaicin (200μmol.L-1); high zinc culture group: cultured byzinc chloride (30μmolL-1) for24h, then add capsaicin (200μmol.L-1). Then, cellswere collected respectively,1min,5min,7min and10min after adding capsaicin.Immunocytochemistry, immunoblotting and image analysis techniques wereused to detect the effect of zinc on the CGRP expression in neurons.ResultsAfter injection of capsaicin, the animals appear rejection foot and limp andher independent behavioral changes, mechanical pain threshold and thermalpain threshold decreased. High zinc feeding can significantly reduce animalautonomous behavioral changes, up regulate mechanical pain threshold andthermal pain threshold. Low zinc feeding can up-regulate the pain sensitivity,mechanical pain threshold and thermal pain threshold lower (P<0.01). Inaddition, high zinc feeding can significantly, down-regulate the expression ofCGRP in spinal cord and cultured neurons, while low zinc feeding candown-regulate the expression of CGRP (P<0.01).ConclusionsZinc can inhibit the expression of CGRP in NPP spinal cord and culturedneuron.Zinc can inhibit NPP.