title: A novel hot-plate test sensitive to hyperalgesic stimuli and non-opioid analgesics.
abstract: It is widely accepted that the classical constant-temperature hot-plate test is insensitive to cyclooxygenase inhibitors. In the current study, we developed a variant of the hot-plate test procedure (modified hot-plate (MHP) test) to measure inflammatory nociception in freely moving rats and mice. Following left and right hind paw stimulation with a phlogogen and vehicle, respectively, the animals were placed individually on a hot-plate surface at 51 degrees C and the withdrawal latency for each paw was determined simultaneously in measurements performed at 15, 60, 180, and 360 min post-challenge. Plantar stimulation of rats (250 and 500 microg/paw) and mice (125-500 microg/paw) with carrageenan led to a rapid hyperalgesic response of the ipsilateral paw that reached a plateau from 15 to 360 min after challenge. Pretreatment with indomethacin (4 mg/kg, i.p.) inhibited the phenomenon at all the times analyzed. Similarly, plantar stimulation of rats and mice with prostaglandin E2 (0.5 and 1 microg/paw) also resulted in rapid hyperalgesia which was first detected 15 min post-challenge. Finally, we observed that the MHP test was more sensitive than the classical Hargreaves' test, being able to detect about 4- and 10-fold lower doses of prostaglandin E2 and carrageenan, respectively. In conclusion, the MHP test is a simple and sensitive method for detecting peripheral hyperalgesia and analgesia in rats and mice. This test represents a low-cost alternative for the study of inflammatory pain in freely moving animals.
authors.affiliation: Laboratório de Inflamação, Departamento de Fisiologia e Farmacodinâmica, Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, RJ, Brasil.
authors.forename: T R
authors.initials: TR
authors.lastname: Lavich
authors.forename: R S B
authors.initials: RS
authors.lastname: Cordeiro
authors.forename: P M R
authors.initials: PM
authors.lastname: Silva
authors.forename: M A
authors.initials: MA
authors.lastname: Martins
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002351:Carrageenan; D015232:Dinoprostone; D005260:Female; D006358:Hot Temperature; D006930:Hyperalgesia / Q000139:chemically induced* / Q000188:drug therapy; D007213:Indomethacin / Q000494:pharmacology*; D008297:Male; D051379:Mice; D010147:Pain Measurement / Q000187:drug effects / Q000295:instrumentation*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D002351:Carrageenan; D015232:Dinoprostone; D007213:Indomethacin