title: Esthesiometric evaluations of corneal anesthesia and prolonged analgesia in rabbits.
abstract: Esthesiometry was used to evaluate prolonged corneal analgesia, induced by repeated intramuscular injections in New Zealand White rabbits of 2.3 to 4.9 kg body weight of two analgesics: meperidine (10 mg/kg) or buprenorphine (200 micrograms/kg) following short term anesthesia induced by ketamine (35 mg/kg) and xylazine (5 mg/kg). The surface pressure was calculated, using data supplied by the manufacturer, for the fiber length just sufficient to elicit the corneal reflex. Thus the corneal reflex was used as a proxy for pain. For the 12 injections of meperidine, at 2 hr intervals, the surface pressure peaked one hour after each injection of meperidine, and subsequently declined at the next hour when the injection was repeated resulting in a saw-tooth pattern of responsiveness. For the 5 injections of buprenorphine, at 5 hr intervals, the surface pressure to elicit the corneal reflex rose after a second injection to overlap the pressures generated by meperidine. The consistent analgesia continued until after 24 hours. Accordingly long-term analgesia may be conveniently measured using a quantitative technique, esthesiometry. Comparison of the two regimens suggests buprenorphine is preferred over meperidine in experiments that require sustained analgesic coverage for periods of 24 hours.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, University of Western Ontario, London, Canada.
authors.forename: J R
authors.initials: JR
authors.lastname: Trevithick
authors.forename: T
authors.initials: T
authors.lastname: Dzialoszynski
authors.forename: M
authors.initials: M
authors.lastname: Hirst
authors.forename: A P
authors.initials: AP
authors.lastname: Cullen
mesh_terms: D000698:Analgesia / Q000379:methods*; D000779:Anesthetics, Local; D000827:Animal Welfare; D000818:Animals; D002047:Buprenorphine / Q000008:administration & dosage; D003315:Cornea / Q000187:drug effects* / Q000528:radiation effects; D007649:Ketamine / Q000008:administration & dosage; D008614:Meperidine / Q000008:administration & dosage; D011817:Rabbits; D014991:Xylazine / Q000008:administration & dosage
chemical_list: D000779:Anesthetics, Local; D014991:Xylazine; D002047:Buprenorphine; D007649:Ketamine; D008614:Meperidine