Hot and cold nociception are genetically correlated

Recent experiments in our laboratory have revealed a genetic correlation of the sensitivity of inbred mouse strains to different assays of nociception using noxious heat stimuli. An open question is whether the property of th e noxious stimulus underlying the genetic correlation is heat specifically or simply a temperature (hot or cold) in the noxious range. The existing el ectrophysiological, psychophysical, neurochemical, and functional imaging l iteratures regarding the relationship of heat pain and cold pain are quite contentious, with a number of similarities and dissociations being document ed. In the present study, we tested 12 inbred mouse strains (129/J, A/J, AK R/J, BALB/cJ, C3H/HeJ, C57BL/6J, C57BL/10J, C58/J, CBA/J, DBA/2J, RIIIS/J, and SM/J) for their reflexive withdrawal sensitivity to immersion of the ta il in hot (47.5 degrees C) and cold (-15 degrees C) water and compared the observed latencies with those obtained previously, using a 49 degrees C sti mulus. All three traits displayed substantial heritabilities, ranging from 0.41 to 0.50. Strain means on these nociceptive traits displayed a high deg ree of cross-correlation (r = 0.49-0.77). Genetic correlation of hot and co ld nociception implies that similar genes underlie interindividual variabil ity in both traits in mice and further suggests that these nociceptive type s share physiological mediation. This finding is discussed in relation to e xisting data in other mammals including humans.