title: Gene knockdown of the N-methyl-D-aspartate receptor NR1 subunit with subcutaneous small interfering RNA reduces inflammation-induced nociception in rats.
abstract: BACKGROUND
  Spinal N-methyl-D-aspartate receptors have been demonstrated to play an important role in the facilitation and maintenance of nociception. To avoid adverse effects of blocking N-methyl-D-aspartate receptors in the central nervous system, blocking N-methyl-D-aspartate receptor in peripheral nervous system is an ideal alternative. Transfection of small interfering RNAs (siRNAs) into cells has been revealed to provide potent silencing of specific genes. In this study, the authors examined the effect of subcutaneous injection of siRNA targeting the NR1 subunit of the N-methyl-D-aspartate receptor on silencing NR1 gene expression and subsequently abolishing inflammatory nociception in rats.
  
  
  METHODS
  Male Sprague-Dawley rats received intradermal injection of NR1 siRNA and underwent injection of formalin or complete Freund's adjuvant. The flinch response and mechanical hypersensitivity by von Frey filaments were assessed. Then the messenger RNA and protein of NR1 in skin and dorsal root ganglion were analyzed.
  
  
  RESULTS
  The results revealed that subcutaneous injection of 1 nmol NR1 siRNA effectively diminished the nociception induced by formalin and complete Freund's adjuvant stimuli and attenuated the level of NR1 messenger RNA and protein in skin and ipsilateral dorsal root ganglion. The antinociception effect and the inhibition of NR1 expression persisted for about 7 days after administration of NR1 siRNA.
  
  
  CONCLUSIONS
  The data of this study suggest that NR1 siRNA has potential therapeutic value in the treatment of inflammatory pain induced or maintained by peripheral nociceptor activity and support the potential application of this method to the study of nociceptive processes and target the validation of pain-associated genes.
authors.affiliation: Department of Anesthesiology, E-DA Hospital, I-Shou University, Kaohsiung, Taiwan. tanphphd@hotmail.com
authors.forename: Ping-Heng
authors.initials: PH
authors.lastname: Tan
authors.forename: Yuan-Yi
authors.initials: YY
authors.lastname: Chia
authors.forename: Lok-Hi
authors.initials: LH
authors.lastname: Chow
authors.forename: Jieh-Jie
authors.initials: JJ
authors.lastname: Chen
authors.forename: Lin-Cheng
authors.initials: LC
authors.lastname: Yang
authors.forename: Kuo-Chuan
authors.initials: KC
authors.lastname: Hung
authors.forename: Hung-Shu
authors.initials: HS
authors.lastname: Chen
authors.forename: Chien-Hung
authors.initials: CH
authors.lastname: Kuo
mesh_terms: D000818:Animals; D005557:Formaldehyde; D005620:Freund's Adjuvant; D055785:Gene Knockdown Techniques / Q000379:methods*; D018836:Inflammation Mediators / Q000008:administration & dosage* / Q000502:physiology; D007279:Injections, Subcutaneous; D008297:Male; D010146:Pain / Q000235:genetics / Q000378:metabolism* / Q000517:prevention & control*; D010147:Pain Measurement / Q000379:methods; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000172:deficiency* / Q000235:genetics
chemical_list: D018836:Inflammation Mediators; C409466:NR1 NMDA receptor; D034741:RNA, Small Interfering; D016194:Receptors, N-Methyl-D-Aspartate; D005557:Formaldehyde; D005620:Freund's Adjuvant