THE EFFECT OF GENOTYPE ON SENSITIVITY TO INFLAMMATORY NOCICEPTION - CHARACTERIZATION OF RESISTANT (A J) AND SENSITIVE (C57BL/6J) INBRED MOUSE STRAINS/

The important role of genetic factors in the mediation of sensitivity to pain and pain inhibition is being increasingly appreciated. In an a ttempt to systematically study the genotypic influences on inflammator y nociception, we conducted a survey of the nociceptive responsivity o f three common outbred mouse strains and 11 inbred mouse strains on th e formalin test. The formalin test is known to display a biphasic temp oral pattern of behavioral and electrophysiological activity, defined by an acute/early phase and a tonic/late phase. Nociceptive sensitivit y (licking/biting of the affected area) to a subcutaneous injection of 5% formalin (25 mu 1 volume) into the plantar surface of the right hi ndpaw displayed moderate heritability in both phases (0.38 and 0.46, r espectively). One strain, A/J, was identified as extremely resistant t o formalin nociception, displaying total licking in the acute and toni c phases that was 60% and 87% lower, respectively, than the grand mean of all strains. A subsequent series of experiments were performed to characterize the difference between A/J and C57BL/6J mice. The finding s establish this inbred strain comparison as a useful genetic model of nociceptive sensitivity. (C) 1998 International Association for the S tudy of Pain. Published by Elsevier Science B.V.