Effects Of Adrenomedullin And MrgC Receptors On Satellite Glial Cells In DRG

Adrenomedullin(AM)is a member of calcitonin gene-related peptide(CGRP)family which is built by 52 amino acids.AM is a inflammatory factor while its function in chronic pain is currently remaining unknown.In the past,our laboratory used AM to act in astrocytes cultured in vitro and found that AM was able to activate astrocytes.Spinal astrocytes and satellite glial cells(SGCs)in dorsal root ganglia(DRG)are the same cell type at different locations.Based on this idea,using the techniques of DRG cultures to observe whether AM can activate satellite glial cells.Activation of glial cells in the spinal cord such as microglia and astrocytes have been shown to be involved in the regulation of morphine tolerance and hyperalgesia.This is due to the expression of proinflammatory cytokines in the spinal cord,including mainly interleukin-1 beta(IL-1?)and tumor necrosis factor(TNF-a).However,there is little research on the activation of glial cells in the peripheral nervous system(PNS).The main research of this paper:1?the influence of AM on satellite glial cells in DRG(from the two aspects of morphology and functions).It has been found that pain occurs when satellite glial cells are activated.AM could up-regulate glial fibrillary acidic proteins(GFAP),GFAP is a specific marker of activated satellite glial cells.2?the effect of activated MrgC receptors(Mas-related gene(Mrg)C receptors)on chronic morphine-activated satellite glial cells.It has been found that activation of MrgC receptors can inhibit morphine tolerance,activation of satellite glial cells is an important mechanism of morphine tolerance.thus we want to observe whether activation of MrgC receptors can inhibit the activation of satellite glial cells.In this study,in vitro tissue culture,immunofluorescence staining and Western Blotting(Western Blotting)and other experimental techniques:(1)the influence of AM on SGCs in cultured DRG;the impacts of inhibition of satellite glial cells' activity on AM-induced CGRP and nNOS in DRG neurons.(2)the influence of MrgC bovine adrenal medulla peptide 8-22(BAM8-22)on SGCs following the application of chronic morphine to the cultured DRG.The results showed that:(1)exogenous addition of AM in cultured DRG,satellite glial cells could be activated.When the AM receptor antagonist AM22-52 was added,AM could no longer activate the satellite glial cells.AM induced the increase of expression of CGRP and nNOS in neurons.Exposure of DRG cultures to fluorocitric acid(FC)which could inhibit the activation of SGCs suppressed the AM-induced expressions of CGRP and nNOS;(2)following exposure cultured DRG to chronic morphine,immunoblotting showed that chronic morphine increased the expression of GFAP protein in DRG.After adding BAM8-22,the expression of GFAP protein in DRG decreased.These results suggest that AM can activate satellite glial cells in DRG and increase the expression of CGRP and nNOS in neurons by satellite glial cells.Activation of MrgC receptors inhibits chronic morphine-induced the activation of satellite glial cells.