title: Effects of fentanyl administration on locomotor response in horses with the G57C μ-opioid receptor polymorphism.
abstract: OBJECTIVE To determine the locomotor response to the administration of fentanyl in horses with and without the G57C polymorphism of the μ-opioid receptor. ANIMALS 20 horses of various breeds and ages (10 horses heterozygous for the G57C polymorphism and 10 age-, breed-, and sex-matched horses that did not have the G57C polymorphism). PROCEDURES The number of steps each horse took was counted over consecutive 2-minute periods for 20 minutes to determine a baseline value. The horse then received a bolus of fentanyl (20 μg/kg, IV), and the number of steps was again counted during consecutive 2-minute periods for 60 minutes. The mean baseline value was subtracted from each 2-minute period after fentanyl administration; step counts with negative values were assigned a value of 0. Data were analyzed by use of a repeated-measures ANOVA. RESULTS Data for 19 of 20 horses (10 horses with the G57C polymorphism and 9 control horses without the G57C polymorphism) were included in the analysis. Horses with the G57C polymorphism had a significant increase in locomotor activity, compared with results for horses without the polymorphism. There was a significant group-by-time interaction. CONCLUSIONS AND CLINICAL RELEVANCE Horses heterozygous for the G57C polymorphism of the μ-opioid receptor had an increased locomotor response to fentanyl administration, compared with the response for horses without this polymorphism. The clinical impact of this finding should be investigated.
authors.forename: Lois A
authors.initials: LA
authors.lastname: Wetmore
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Pascoe
authors.forename: Yael
authors.initials: Y
authors.lastname: Shilo-Benjamini
authors.forename: Jane C
authors.initials: JC
authors.lastname: Lindsey
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D005260:Female; D005283:Fentanyl / Q000008:administration & dosage / Q000494:pharmacology*; D006736:Horses / Q000235:genetics / Q000502:physiology*; D007262:Infusions, Intravenous / Q000662:veterinary; D008124:Locomotion / Q000187:drug effects*; D008297:Male; D020641:Polymorphism, Single Nucleotide; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors / Q000235:genetics*
chemical_list: D000701:Analgesics, Opioid; D017450:Receptors, Opioid, mu; D005283:Fentanyl