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. Author manuscript; available in PMC: 2015 May 1.
Published in final edited form as: Pain. 2013 Sep 24;155(5):868–880. doi: 10.1016/j.pain.2013.09.018

Fig. 2.

Fig. 2

Multivariate analyses plots illustrating cross-correlations among inbred strain means for 31 assays of nociception and hypersensitivity. (A) PCA plot illustrating the first two unrotated principle components. The angle between rays projecting to the assays’ points is representative of their correlation: close to 0° indicates high positive correlations; close to 180° indicates high negative correlations; close to 90° indicates uncorrelated assays. The proportion of total variance accounted for by the two factors is 0.52. (B) MDS plot illustrating the cross-correlations in which the Euclidean distances between assays are representative of their correlation such that higher positive correlations are closer. The proportion of total variance accounted for is 0.74. A Kruskal loss function with monotonic regression was employed, resulting in a final stress of 0.23. Both plots show that thermal nociception assays in otherwise naïve mice (HP, HT, TF, TW−15, TW47.5, TW49) and assays of spontaneous nociceptive responses to chemical/inflammatory stimuli in otherwise naïve mice (ACAA, AAMS, BV, CAP, FEarly, FLate) continue to cluster together (Fig. 2B), respectively, indicating strong genetic relatedness as previously [17,25]. Cold hypersensitivity assays (PACACET, PACCOLD, SNIACET, ZYMACET) are shown to be positively correlated with thermal nociception assays. Note that graphical misrepresentation of the pairwise correlations with assays DYNVF and PNIVF exists in both PCA and MDS plots, as discussed in the text and indicated with parentheses around the assay labels. Font color refers to the genetically distinct type of nociception or hypersensitivity identified previously [17]: (red) thermal nociception in otherwise naïve mice; (green) spontaneous responses to noxious chemical/inflammatory stimuli; (orange) thermal hypersensitivity; (blue) mechanical hypersensitivity; (purple) afferent input-dependent hypersensitivity. Brown font refers to mechanical sensitivity in otherwise naïve mice and mechanical nociception. Black font is used for assays newly included in the current analysis.