title: Peripheral inflammation alters desensitization of substance P-evoked current in rat dorsal root ganglion neurons.
abstract: The neuropeptide substance P is synthesized in a proportion of neurons of the peripheral and central nervous system, and the receptor for substance P, tachykinin NK₁ receptor, has been identified in numerous areas of the central nervous system including the spinal cord. The present investigation was to confirm the existence of tachykinin NK₁ receptor on rat dorsal root ganglion (DRG) neurons and characterize the adaptation of inward current evoked by substance P during carrageenan-induced peripheral inflammation. Using whole-cell voltage recording technique, our results demonstrated that 1 μM substance P elicited significant inward current in a small population of small-diameter DRG neurons of control rats (7%, n=218) and in a bigger proportion of DRG neurons of carrageenan-inflamed rats (15%, n=203). Desensitization of substance P-evoked current was exhibited in almost all of substance P-responsive DRG neurons in control rats (94%, n=16), while it diminished in a bigger proportion of DRG neurons (35%, n=31) in inflamed rats. Furthermore, desensitization of substance P-evoked current was recovered by the activation of protein kinase C (PKC) by application of phorbol 12,13-dibutyrate, a selective agonist of PKC, in the DRG neurons of the inflamed rats. All these results indicated that tachykinin NK₁ receptor in the primary afferents might contribute to the development and maintenance of inflammatory pain.
authors.affiliation: Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 20032, China. bieb@ccf.org
authors.forename: Bihua
authors.initials: B
authors.lastname: Bie
authors.forename: Zhi-Qi
authors.initials: ZQ
authors.lastname: Zhao
mesh_terms: D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects*; D005727:Ganglia, Spinal / Q000473:pathology*; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D008297:Male; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D017933:Peripheral Nervous System / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018040:Receptors, Neurokinin-1 / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology*
chemical_list: D018040:Receptors, Neurokinin-1; D013373:Substance P