Effect of romifidine on the nociceptive withdrawal reflex and temporal summation in conscious horses.
OBJECTIVE
To investigate the action of a single IV administration of romifidine on the thresholds of the nociceptive withdrawal reflex (NWR) and temporal summation in conscious horses.


METHODS
10 adult horses.


METHODS
Single electrical stimulations were applied on the digital nerves to evoke NWR from the left forelimb and hind limb. Repeated electrical stimulations (10 stimuli, 5 Hz) were given to obtain temporal summation. Surface electromyographic reflex activity was recorded from the common digital extensor and cranial tibial muscles. After baseline assessment of NWR and temporal summation thresholds, romifidine (80 microg x kg(-1), IV) was administered. Successive determinations of NWR and temporal summation thresholds were performed 5, 25, and 55 minutes after administration.


RESULTS
Romifidine significantly increased the current intensities necessary to evoke NWR and temporal summation in forelimbs and hind limbs of horses. Values were significantly higher than baseline values 55 minutes after romifidine administration. After administration of romifidine, a facilitation of reflex components of tactile origin was observed when repeated stimulations were applied.


CONCLUSIONS
Results confirm antinociceptive activity of romifidine and may represent an objective demonstration of the well-known hypersensitivity to tactile stimuli observed in horses receiving alpha2-adrenoreceptor agonists in clinical practice. Romifidine can be included in analgesic and anesthetic protocols to provide additional analgesia in horses.
Spadavecchia
Claudia
C
Anesthesiology Section, Department of Clinical Veterinary Sciences, Vetsuisse Faculty, University of Berne, Switzerland.
Arendt-Nielsen
Lars
L
Andersen
Ole K
OK
Spadavecchia
Luciano
L
Schatzmann
Urs
U
D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D004576:Electromyography / Q000662:veterinary; D005260:Female; D005552:Forelimb; D006614:Hindlimb; D006736:Horses / Q000502:physiology*; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D007275:Injections, Intravenous / Q000662:veterinary; D008297:Male; D010147:Pain Measurement / Q000187:drug effects* / Q000662:veterinary*; D012018:Reflex / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D007093:Imidazoles; C076257:romifidine