title: The L-kynurenine-probenecid combination reduces neuropathic pain in rats.
abstract: BACKGROUND
  l-Kynurenine has antinociceptive effects in acute and inflammatory pain. This study determined the effect of l-kynurenine and its metabolite (kynurenic acid) on rats subjected to neuropathic pain.
  
  
  METHODS
  L5/L6 spinal nerve ligation induced tactile allodynia as measured with von Frey filaments using the up-down method. High-performance liquid chromatography and Western blot analysis determined kynurenic acid levels and expression of kynurenine amino transferase II (KAT II), respectively.
  
  
  RESULTS
  l-Kynurenine (50-200 mg/kg, i.p.) or probenecid (100 mg/kg, i.p.) did not affect allodynia in neuropathic rats. In contrast, l-kynurenine (50-200 mg/kg, i.p.) in combination with probenecid (100 mg/kg, i.p.), an inhibitor of organic anion transport, reversed allodynia. Furthermore, intrathecal kynurenic acid (1-30 μg) reversed allodynia. Probenecid (100 mg/kg, i.p.) supplementation enhanced the maximal antiallodynic effect of intrathecal kynurenic acid (10 μg). Only the combined administration of l-kynurenine (200 mg/kg)/probenecid (100 mg/kg) increased the kynurenic acid concentration in cerebrospinal fluid. KAT II is expressed in dorsal root ganglia and dorsal spinal cord. KAT II expression was unchanged by the spinal nerve ligation or l-kynurenine/probenecid combination. The kynurenine/probenecid combination did not affect motor activity.
  
  
  CONCLUSIONS
  l-Kynurenine produces its antiallodynic effect in the central nervous system through kynurenic acid. This effect may result from blockade of N-methyl-d-aspartate receptors. KAT II is expressed in dorsal root ganglion and dorsal spinal cord. Combined l-kynurenine and probenecid therapy has the potential to reduce neuropathic pain in humans.
authors.affiliation: Departamento de Farmacobiología, Centro de Investigación y de Estudios Avanzados (Cinvestav), Sede Sur, México, D.F., Mexico.
authors.forename: J B
authors.initials: JB
authors.lastname: Pineda-Farias
authors.forename: F
authors.initials: F
authors.lastname: Pérez-Severiano
authors.forename: D F
authors.initials: DF
authors.lastname: González-Esquivel
authors.forename: P
authors.initials: P
authors.lastname: Barragán-Iglesias
authors.forename: M
authors.initials: M
authors.lastname: Bravo-Hernández
authors.forename: C
authors.initials: C
authors.lastname: Cervantes-Durán
authors.forename: P
authors.initials: P
authors.lastname: Aguilera
authors.forename: C
authors.initials: C
authors.lastname: Ríos
authors.forename: V
authors.initials: V
authors.lastname: Granados-Soto
mesh_terms: D000818:Animals; D004359:Drug Therapy, Combination; D005260:Female; D006930:Hyperalgesia / Q000188:drug therapy*; D007737:Kynurenine / Q000494:pharmacology / Q000627:therapeutic use*; D009043:Motor Activity / Q000187:drug effects; D009437:Neuralgia / Q000188:drug therapy*; D010147:Pain Measurement; D011339:Probenecid / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D013116:Spinal Cord / Q000187:drug effects
chemical_list: D007737:Kynurenine; D011339:Probenecid