title: Effects of epidural capsaicin on nociceptive threshold and neurological functions in rabbits.
abstract: Capsaicin, as a principle active component of Chili peppers, is popularly consumed by many people around the world. Whether capsaicin-induced neuropathy alters the function of sensory neurons is still unknown.
  
  
  OBJECTIVE
  The objectives of this study were to determine the effects of epidural capsaicin on nociceptive threshold and neurological functions in a rabbit model.
  
  
  METHODS
  An intrathecal injection system was set up using a rabbit model. Rabbits were treated with capsaicin at doses of 0.04, 0.10, and 0.20 mg/kg once. The changes in neurological functions and morphology of the spinal cord and spinal nerve roots were determined within 24 hours. Changes in the nociceptive threshold in the hind limbs of the rabbits were observed for 30 days.
  
  
  METHODS
  Capsaicin's effect on the changing neurological functions was evaluated by the neurological functional scores. The structural changes of spinal cord and spinal nerve roots were observed by hematoxylin and eosin staining and transmission electron microscopy. The nociceptive threshold changes in the rabbits were measured by the responding time for pain induced by a thermostimulation.
  
  
  RESULTS
  The results showed that capsaicin reversed changes in the neurological function of rabbit hindlimbs. In the 0.10 and 0.20 mg/kg groups, structural abnormalities were found in the rabbit's spinal nerves. Capsaicin also significantly increased the pain threshold in rabbits when compared with the control group (P < 0.05 or P < 0.01). The maximum values of pain threshold were found in the 0.10 mg/kg capsaicin group after 3 days of capsaicin treatment.
  
  
  CONCLUSIONS
  With the exception of a potential toxicity, capsaicin may be a potential candidate agent for providing pain relief of both neuropathic and nociceptive conditions.
authors: Department of Anesthesiology, First Clinic Hospital, Harbin Medical University, 23 YouZheng Street, NanGang, Harbin, China. dongyingwei666@163.com
authors: Ying-Wei
authors: YW
authors: Dong
authors: Fan
authors: F
authors: Zhang
authors: Li
authors: L
authors: Liu
authors: Jia-Ren
authors: JR
authors: Liu
mesh_terms: D000818:Animals; D002211:Capsaicin / Q000008:administration & dosage / Q000494:pharmacology*; D006614:Hindlimb / Q000294:innervation; D006801:Humans; D007278:Injections, Spinal; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure; D017288:Pain Threshold / Q000187:drug effects*; D011817:Rabbits; D018689:Sensory System Agents / Q000008:administration & dosage / Q000494:pharmacology*; D013116:Spinal Cord / Q000166:cytology / Q000187:drug effects / Q000473:pathology; D013126:Spinal Nerve Roots / Q000187:drug effects / Q000473:pathology / Q000648:ultrastructure
chemical_list: D018689:Sensory System Agents; D002211:Capsaicin