title: Inbred strain differences in morphine-induced analgesia with the hot plate assay: a reassessment.
abstract: Using the hot plate assay of analgesia, several investigators have reported DBA/2J mice to be much more sensitive to morphine and other opioids than C57BL/6J mice using paw-lick as the behavioral end point. In the present studies, we compared DBA/2J, C57BL/6J, and C3H/HeJ mice on two behavioral end points, either (1) the initial response to the hot plate, either a hind paw-lift, paw-shake, or paw-lick, whichever occurred first, or (2) the paw-lick response. In response to either morphine or saline, all three strains showed roughly equivalent latencies to the initial response, but the DBA/2J strain was markedly slow to show paw-lick as a nocifensive response compared to the C57BL/6J strain. As a result, only for the paw-lick response were there significant differences among the three inbred strains in morphine analgesia. Thus, differences in analgesic sensitivity among these strains are largely a function of the behavioral end point used to assess nociception to the hot plate.
authors.affiliation: Research Service, VA Medical Center, Portland, Oregon 97201.
authors.forename: J K
authors.initials: JK
authors.lastname: Belknap
authors.forename: M
authors.initials: M
authors.lastname: Lamé
authors.forename: P W
authors.initials: PW
authors.lastname: Danielson
mesh_terms: D000818:Animals; D006614:Hindlimb; D006358:Hot Temperature; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H / Q000235:genetics; D008810:Mice, Inbred C57BL / Q000235:genetics; D008811:Mice, Inbred DBA / Q000235:genetics; D009020:Morphine / Q000494:pharmacology*; D010147:Pain Measurement; D011930:Reaction Time / Q000235:genetics
chemical_list: D009020:Morphine