title: Local administration of delta9-tetrahydrocannabinol attenuates capsaicin-induced thermal nociception in rhesus monkeys: a peripheral cannabinoid action.
abstract: BACKGROUND
  Cannabinoids can reduce nociceptive responses by acting on peripheral cannabinoid receptors in rodents.
  
  
  OBJECTIVE
  The study was conducted to evaluate the hypothesis that local administration of delta9-tetrahydrocannabinol (delta9-THC) can attenuate capsaicin-induced nociception in rhesus monkeys.
  
  
  METHODS
  Capsaicin (100 microg) was applied locally in the tail of rhesus monkeys to evoke a nociceptive response, thermal allodynia, in normally innocuous 46 degrees C water. delta9-THC (10-320 microg) was coadministered with capsaicin in the tail to assess local antinociceptive effects. In addition, a local antagonism study was performed to confirm the selectivity of delta9-THC action.
  
  
  RESULTS
  delta9-THC dose-dependently inhibited capsaicin-induced allodynia. This local antinociception was antagonized by small doses (10-100 microg) of the cannabinoid CB1 antagonist, SR141716A, applied in the tail. However, 100 microg SR141716A injected subcutaneously in the back did not antagonize local delta9-THC.
  
  
  CONCLUSIONS
  These results indicate that the site of action of locally applied delta9-THC is in the tail. It provides functional evidence that activation of peripheral cannabinoid CB1 receptors can attenuate capsaicin-induced thermal nociception in non-human primates and suggests a new approach for cannabinoids in pain management.
authors.affiliation: Department of Pharmacology, University of Michigan, Medical School, Ann Arbor 48109-0632, USA. mko@umich.edu
authors.forename: M C
authors.initials: MC
authors.lastname: Ko
authors.forename: J H
authors.initials: JH
authors.lastname: Woods
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002186:Cannabinoids / Q000008:administration & dosage / Q000037:antagonists & inhibitors; D002211:Capsaicin / Q000494:pharmacology; D013759:Dronabinol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D008253:Macaca mulatta; D008297:Male; D010147:Pain Measurement / Q000187:drug effects*; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology; D011720:Pyrazoles / Q000008:administration & dosage / Q000494:pharmacology; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000037:antagonists & inhibitors; D000077285:Rimonabant
chemical_list: D018712:Analgesics, Non-Narcotic; D002186:Cannabinoids; D010880:Piperidines; D011720:Pyrazoles; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; D013759:Dronabinol; D000077285:Rimonabant; D002211:Capsaicin