title: Quantitative assessment of nociception in horses by use of the nociceptive withdrawal reflex evoked by transcutaneous electrical stimulation.
abstract: OBJECTIVE
  To evoke and measure the nociceptive withdrawal reflex (NWR) by use of electromyographic recordings and to score the behavioral nociceptive responses to electrical pulses in standing nonsedated horses.
  
  
  METHODS
  10 adult horses.
  
  
  METHODS
  The lateral palmar digital nerve of the forelimb was transcutaneously stimulated, and surface electromyographic responses were recorded from the ulnaris lateralis, extensor carpi radialis, and common digital extensor muscles. Stimuli consisted of a 25-millisecond train of 5 constant-current pulses delivered by a computer-controlled stimulator. The 80- to 250-milliseconds poststimulation interval was analyzed to detect the NWR. The current intensity was increased in steps of 0.5 mA until the NWR threshold intensity (lt) was reached. The stimulus at It was repeated twice. Latency and amplitude of the NWR, together with the behavioral reaction of horses, were analyzed. The latter was scored according to a scale from 0 (no reaction) to 5 (vigorous reaction). Finally, 3 suprathreshold stimuli at 1.2 X It were analyzed.
  
  
  RESULTS
  The median It to elicit NWR was 2.5 mA. Median onset latency of the NWR was 96.0 milliseconds at It and 89.6 milliseconds for suprathreshold stimuli. The amplitude of the reflexes was higher for suprathreshold stimulations, and behavioral reactions were slightly stronger when stimulus intensity increased.
  
  
  CONCLUSIONS
  Results of our study indicate that it is possible to record NWR in conscious standing horses, to define a reflex threshold, and to measure reflexes in response to increasing stimulus intensity.
authors.affiliation: Department of Clinical Veterinary Medicine, University of Berne, Switzerland.
authors.forename: Claudia
authors.initials: C
authors.lastname: Spadavecchia
authors.forename: Luciano
authors.initials: L
authors.lastname: Spadavecchia
authors.forename: Ole K
authors.initials: OK
authors.lastname: Andersen
authors.forename: Lars
authors.initials: L
authors.lastname: Arendt-Nielsen
authors.forename: Massimo
authors.initials: M
authors.lastname: Leandri
authors.forename: Urs
authors.initials: U
authors.lastname: Schatzmann
mesh_terms: D000818:Animals; D004576:Electromyography / Q000662:veterinary; D005260:Female; D006736:Horses / Q000502:physiology* / Q000523:psychology; D008297:Male; D009619:Nociceptors / Q000502:physiology; D010146:Pain / Q000503:physiopathology / Q000662:veterinary*; D010147:Pain Measurement / Q000662:veterinary; D017288:Pain Threshold / Q000502:physiology / Q000523:psychology; D012018:Reflex / Q000502:physiology; D004561:Transcutaneous Electric Nerve Stimulation