Heritability of nociception II. 'Types' of nociception revealed by geneticcorrelation analysis

Clinical pain syndromes, and experimental assays of nociception, are differ entially affected by manipulations such as drug administration and exposure to environmental stress. This suggests that there are different 'types' of pain, We exploited genetic differences among inbred strains of mice in an attempt to define these primary 'types'; that is, to identify the fundament al parameters of pain processing. Eleven randomly-chosen inbred mouse strai ns were tested for their basal sensitivity on I? common measures of nocicep tion, These measures provided for a range of different nociceptive dimensio ns including noxious stimulus modality, location, duration and etiology, am ong others. Since individual members of inbred strains are identical at all genetic loci, the observation of correlated strain means in any given pair of nociceptive assays is an index of genetic correlation between these ass ays, and hence an indication of common physiological mediation, Obtained co rrelation matrices were subjected to multivariate analyses to identify cons tellations of nociceptive assays with common genetic mediation. This analys is revealed three major clusters of nociception: (1) baseline thermal nocic eption, (2) spontaneously emitted responses to chemical stimuli, and (3) ba seline mechanical sensitivity and cutaneous hypersensitivity. Many other no ciceptive parameters that might a priori have been considered closely relat ed proved to bt:genetically divergent. (C) 1999 International Association f or the Study of Pain. Published by Elsevier Science B.V.