title: Assessment of an Orofacial Operant Pain Assay as a Preclinical Tool for Evaluating Analgesic Efficacy in Rodents.
abstract: A model system capable of providing clinically relevant analgesic doses with minimal trauma has been elusive in laboratory animal medicine. Our laboratory has developed an orofacial operant pain system that effectively discriminates between non-noxious and noxious thermal stimuli in rats and mice. Male and female rats (Crl:SD) and mice (Crl:SKR-HR(hr)) were trained to perform a task (placing their face through an opening and having their cheeks stay in contact with thermodes) to receive a reward (a solution of sweetened condensed milk). Currently accepted doses of buprenorphine were tested by using a crossover design. Pain was induced in both species by sensitizing the depilated skin over both cheeks with capsaicin cream or by creating a surgical incision (rats only) and then allowing the animals to contact a temperature-regulated thermode while obtaining a reward. Optimal antinociceptive doses included 0.05 and 0.1 mg/kg in male mice but only 0.05 mg/kg in female mice. In rats, optimal antinociceptive doses included 0.03 and 0.05 mg/kg for male rats but only 0.03 mg/kg for female rats. The 2 pain-induction models in rats (capsaicin cream and surgical incision) did not differ. Our orofacial operant pain assay can determine clinically relevant analgesic doses for rodents in a preclinical assay. The automated, investigator-independent nature of the assay, in conjunction with its high sensitivity, makes this method an improvement over traditional noninvasive methods, providing better data for developing optimal analgesic recommendations for rats and mice.
authors.affiliation: Animal Care Services, University of Florida, Gainesville, Florida, USA.
authors.forename: Harvey E
authors.initials: HE
authors.lastname: Ramirez
authors.affiliation: College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Queeney
authors.affiliation: Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
authors.forename: Misha L
authors.initials: ML
authors.lastname: Dunbar
authors.affiliation: College of Veterinary Medicine, University of Florida, Gainesville, Florida, USA.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Eichner
authors.affiliation: School of Veterinary Medicine, Tuskegee University, Tuskegee, Alabama, USA.
authors.forename: Dania I
authors.initials: DI
authors.lastname: Del Castillo
authors.affiliation: Animal Care Services, University of Florida, Gainesville, Florida, USA.
authors.forename: August H
authors.initials: AH
authors.lastname: Battles
authors.affiliation: Department of Orthodontics, University of Florida, Gainesville, Florida, USA.
authors.forename: John K
authors.initials: JK
authors.lastname: Neubert
mesh_terms: D000700:Analgesics / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000008:administration & dosage; D000818:Animals; D000830:Animals, Laboratory; D002047:Buprenorphine / Q000008:administration & dosage; D003216:Conditioning, Operant; D005157:Facial Pain / Q000188:drug therapy / Q000662:veterinary*; D005260:Female; D008297:Male; D051379:Mice; D010147:Pain Measurement / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012201:Reward; D012376:Rodent Diseases / Q000188:drug therapy*
chemical_list: D000700:Analgesics; D000701:Analgesics, Opioid; D002047:Buprenorphine