Effects of serum immunoglobulins from patients with complex regional pain syndrome (CRPS) on depolarisation-induced calcium transients in isolated dorsal root ganglion (DRG) neurons

Abstract

Complex regional pain syndrome (CRPS) is thought to have an auto-immune component. One such target recently proposed from the effects of auto-immune IgGs on Ca2+ transients in cardiac myocytes and cell lines is the α1-adrenoceptor. We have tested whether such IgGs exerted comparable effects on nociceptive sensory neurons isolated from rat dorsal root ganglia. Depolarisation-induced [Ca2+]i transients were generated by applying 30mM KCl for 2min and monitored by Fura-2 fluorescence imaging. No IgGs tested (including 3 from CRPS patients) had any significant effect on these [Ca2+]i transients. However, IgG from one CRPS patient consistently and significantly reduced the K+-induced response of cells that had been pre-incubated for 24h with a mixture of inflammatory mediators (1μM histamine, 5-hydroxytryptamine, bradykinin and PGE2). Since this pre-incubation also appeared to induce a comparable inhibitory response to the α1-agonist phenylephrine, this is compatible with the α1-adrenoceptor as a target for CRPS auto-immunity. A mechanism whereby this might enhance pain is suggested.