Effect of detomidine on visceral and somatic nociception and duodenal motility in conscious adult horses.
OBJECTIVE
To evaluate the effects of detomidine on visceral and somatic nociception, heart and respiratory rates, sedation, and duodenal motility and to correlate these effects with serum detomidine concentrations.


METHODS
Nonrandomized, experimental trial.


METHODS
Five adult horses, each with a permanent gastric cannula weighing 534 +/- 46 kg.


METHODS
Visceral nociception was evaluated by colorectal (CRD) and duodenal distension (DD). The duodenal balloon was used to assess motility. Somatic nociception was assessed via thermal threshold (TT). Nose-to-ground (NTG) height was used as a measure of sedation. Serum was collected for pharmacokinetic analysis. Detomidine (10 or 20 microg kg(-1)) was administered intravenously. Data were analyzed by means of a three-factor anova with fixed factors of treatment and time and random factor of horse. When a significant time x treatment interaction was detected, differences were compared with a simple t-test or Bonferroni t-test. Significance was set at p < 0.05.


RESULTS
Detomidine produced a significant, dose-dependent decrease in NTG height, heart rate, and skin temperature and a significant, nondose-dependent decrease in respiratory rate. Colorectal distension threshold was significantly increased with 10 microg kg(-1) for 15 minutes and for at least 165 minutes with 20 microg kg(-1). Duodenal distension threshold was significantly increased at 15 minutes for the 20 microg kg(-1) dose. A significant change in TT was not observed at either dose. A marked, immediate decrease in amplitude of duodenal contractions followed detomidine administration at both doses for 50 minutes.


CONCLUSIONS
Detomidine caused a longer period of visceral anti-nociception as determined by CRD but a shorter period of anti-nociception as determined by DD than has been previously reported. The lack of somatic anti-nociception as determined by TT testing may be related to the marked decrease in skin temperature, likely caused by peripheral vasoconstriction and the low temperature cut-off of the testing device.
Elfenbein
Johanna R
JR
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610-0136, USA.
Sanchez
L Chris
LC
Robertson
Sheilah A
SA
Cole
Cynthia A
CA
Sams
Richard
R
D000818:Animals; D019540:Area Under Curve; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects*; D005260:Female; D005769:Gastrointestinal Motility / Q000187:drug effects*; D006207:Half-Life; D006736:Horses / Q000502:physiology*; D006358:Hot Temperature; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D007093:Imidazoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D010146:Pain / Q000188:drug therapy*
D006993:Hypnotics and Sedatives; D007093:Imidazoles; C041255:detomidine