title: Analgesic effects and possible mechanisms of iridoid glycosides from Lamiophlomis rotata (Benth.) Kudo in rats with spared nerve injury.
abstract: BACKGROUND
  Lamiophlomis rotata (Benth.) Kudo (L. rotata) is a medical plant that has been traditionally used for centuries for the treatment of pain, such as bone and muscle pain, joint pain and dysmenorrhea. Although iridoid glycosides of L. rotata (IGLR) are the major active components of it according to reports, it still remains poorly understood about the molecular mechanisms underlying analgesic effects of IGLR. The aim of the present study was to investigate the analgesic effect of IGLR on a spared nerve injury (SNI) model of neuropathic pain.
  
  
  METHODS
  The SNI model in rats was established by complete transection of the common peroneal and tibial distal branches of the sciatic nerve, leaving the sural branch intact. Then SNI rats were treated with IGLR for 14 days, using normal saline as the negative control. The paw withdrawal mechanical threshold (PMWT) in response to mechanical stimulation was measured by von Frey filaments on day 1 before operation and on days 1, 3, 5, 7, 9, 11, 13 and 14 after operation, respectively. After 14 days, the levels of nitric oxide (NO), nitric oxide synthase (NOS), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-10 (IL-10) and cyclic guanosine monophosphate (cGMP) in the spinal dorsal horn were measured by the corresponding kits, mRNA expression of inducible NOS (iNOS) and protein kinase G type I (PKGI) of spinal cord were analyzed by reverse-transcription polymerase chain reaction (RT-PCR). The expression of N-methyl-D-aspartate receptor (NMDAR) and protein kinase C (PKCγ) of the spinal dorsal horn was performed by Western blot. Before all the experiments, motor coordination performance and locomotor activity had been tested.
  
  
  RESULTS
  Our results showed that remarkable mechanical allodynia was observed on day 1 after operation in the SNI model, which was accompanied by a decrease in PMWT. Treatment with IGLR (200, 400, 800mg/kg) significantly alleviated SNI-induced mechanical allodynia, markedly decreased the levels of NO, NOS, TNF-α, IL-1β and cGMP, and increased the level of IL-10. Meanwhile, IGLR (200, 400, 800mg/kg) also inhibited the protein expression of NMDAR, PKCγ and the mRNA expression of iNOS and PKGΙ in the spinal cord. In addition, gavage with the IGLR aqueous extract (800mg/kg) did not signifiantly alter motor coordination or locomotor activity.
  
  
  CONCLUSIONS
  These results indicated IGLR could produce an anti-neuropathic pain effect that might partly be related to the inhibition of the NO/cGMP/PKG and NMDAR/PKC pathways and the level of TNF-α, IL-1β as well as to the increase of the level of IL-10 in spinal cord.
authors.affiliation: College of Pharmacy, South-Central University for Nationalities, Wuhan 430074, China.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: College of Pharmacy, South-Central University for Nationalities, Wuhan 430074, China.
authors.forename: Xuefei
authors.initials: X
authors.lastname: Yin
authors.affiliation: Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, Shanxi 710061, China.
authors.forename: Fuquan
authors.initials: F
authors.lastname: Huo
authors.affiliation: College of Pharmacy, South-Central University for Nationalities, Wuhan 430074, China. Electronic address: xionghui0311020@163.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Xiong
authors.affiliation: College of Pharmacy, South-Central University for Nationalities, Wuhan 430074, China. Electronic address: meizhinan@163.com.
authors.forename: Zhinan
authors.initials: Z
authors.lastname: Mei
mesh_terms: D000700:Analgesics / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D057889:Iridoid Glycosides / Q000494:pharmacology / Q000627:therapeutic use*; D019686:Lamiaceae; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D009437:Neuralgia / Q000188:drug therapy* / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D059348:Peripheral Nerve Injuries / Q000188:drug therapy* / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D045442:Rotarod Performance Test; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism
chemical_list: D000700:Analgesics; D016207:Cytokines; D057889:Iridoid Glycosides; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; C087857:protein kinase C gamma; D017869:Cyclic GMP-Dependent Protein Kinases; D011493:Protein Kinase C; D006152:Cyclic GMP
keywords: Iridoid glycosides; Lamiophlomis rotate (Benth.) Kudo; NMDAR/PKC; NO/cGMP/PKG; Neuropathic pain; Spared nerve injury