Quantitative assessment of nociceptive processes in conscious dogs by use of the nociceptive withdrawal reflex.
OBJECTIVE
To investigate the feasibility of evoking the nociceptive withdrawal reflex (NWR) from fore and hind limbs in conscious dogs, score stimulus-associated behavioral responses, and assess the canine NWR response to suprathreshold stimulations.


METHODS
8 adult Beagles.


METHODS
Surface electromyograms evoked by transcutaneous electrical stimulation of ulnaris and digital plantar nerves were recorded from the deltoideus, cleidobrachialis, biceps femoris, and tibialis cranialis muscles. Train-of-five pulses (stimulus(train)) were used; reflex threshold (I(t train)) was determined, and recruitment curves were obtained at 1.2, 1.5, and 2 x I(t train). Additionally, a single pulse (stimulus(single)) was given at 1, 1.2, 1.5, 2, and 3 x I(t train). Latency and amplitude of NWRs were analyzed. Severity of behavioral reactions was subjectively scored.


RESULTS
Fore- and hind limb I(t train) values (median; 25% to 75% interquartile range) were 2.5 mA (2.0 to 3.6 mA) and 2.1 mA (1.7 to 2.9 mA), respectively. At I(t train), NWR latencies in the deltoideus, cleidobrachialis, biceps femoris, and cranial tibialis muscles were not significantly different (19.6 milliseconds [17.1 to 20.5 milliseconds], 19.5 milliseconds [18.1 to 20.7 milliseconds], 20.5 milliseconds [14.7 to 26.4 milliseconds], and 24.4 milliseconds [17.1 to 40.5 milliseconds], respectively). Latencies obtained with stimulus(train) and stimulus(single) were similar. With increasing stimulation intensities, NWR amplitude increased and correlated positively with behavioral scores.


CONCLUSIONS
In dogs, the NWR can be evoked from limbs and correlates with behavioral reactions. Results suggest that NWR evaluation may enable quantification of nociceptive system excitability and efficacy of analgesics in individual dogs.
Bergadano
Alessandra
A
Department of Clinical Veterinary Medicine, Anaesthesiology Division, Vetsuisse-Faculty, University of Berne, Länggassstrasse 124, PB 8466, CH-3001 Berne, Switzerland.
Andersen
Ole K
OK
Arendt-Nielsen
Lars
L
Schatzmann
Urs
U
Spadavecchia
Claudia
C
D000818:Animals; D003243:Consciousness / Q000502:physiology*; D004285:Dogs / Q000502:physiology*; D008297:Male; D010146:Pain / Q000503:physiopathology / Q000662:veterinary*; D010147:Pain Measurement / Q000662:veterinary*; D017288:Pain Threshold / Q000502:physiology; D012018:Reflex / Q000502:physiology*