title: Antinociceptive effect of buprenorphine and evaluation of the nociceptive withdrawal reflex in foals.
abstract: OBJECTIVE
  To elicit and evaluate the NWR (nociceptive withdrawal reflex) in 2 and 11 day old foals, to investigate if buprenorphine causes antinociception and determine if the NWR response changes with increasing age. The effect of buprenorphine on behaviour was also evaluated.
  
  
  METHODS
  Prospective, experimental cross-over trial.
  
  
  METHODS
  Nine Norwegian Fjord research foals.
  
  
  METHODS
  Buprenorphine, 10 μg kg(-1) was administered intramuscularly (IM) to the same foal at 2 days and at 11 days of age. The NWR and the effect of buprenorphine were evaluated by electromyograms recorded from the left deltoid muscle following electrical stimulation of the left lateral palmar nerve at the level of the pastern. Mentation, locomotor activity and respiratory rate were recorded before and after buprenorphine administration.
  
  
  RESULTS
  We were able to evoke the NWR and temporal summation in foals using this model. Buprenorphine decreased the root mean square amplitude following single electrical stimulation (p < 0.001) in both age groups, and increased the NWR threshold following single electrical stimulation in 2 day old foals (p = 0.0012). Repeated electrical stimulation at 2 Hz was more effective to elicit temporal summation compared to 5 Hz (p < 0.001). No effect of age upon the NWR threshold was found (p = 0.34). Sedation when left undisturbed (11 occasions), increased locomotor activity when handled (9 occasions) and tachypnea (13 occasions) were common side-effects of buprenorphine.
  
  
  CONCLUSIONS
  These findings indicate that buprenorphine has antinociceptive effect in foals. Opioid side effects often recognized in adult horses also occur in foals.
authors.affiliation: Department of Companion Animal Clinical Sciences, Faculty of Veterinary Medicine and Biosciences, Norwegian University of Life Sciences, Oslo, Norway.
authors.forename: Åse I
authors.initials: ÅI
authors.lastname: Risberg
authors.forename: Claudia
authors.initials: C
authors.lastname: Spadavecchia
authors.forename: Birgit
authors.initials: B
authors.lastname: Ranheim
authors.forename: Eli H S
authors.initials: EH
authors.lastname: Hendrickson
authors.forename: Andreas
authors.initials: A
authors.lastname: Lervik
authors.forename: Henning A
authors.initials: HA
authors.lastname: Haga
mesh_terms: D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002047:Buprenorphine / Q000008:administration & dosage / Q000494:pharmacology*; D018592:Cross-Over Studies; D006736:Horses; D059225:Nociception / Q000187:drug effects*; D010147:Pain Measurement / Q000662:veterinary*; D012018:Reflex / Q000187:drug effects*
chemical_list: D000701:Analgesics, Opioid; D002047:Buprenorphine
keywords: buprenorphine; electromyogram; foals; nociceptive threshold; nocieptive withdrawal reflex