Figure 3.

Analysis of intensity distribution for the opioid receptor genes Oprm1 and Oprd1. The finding that Trpv1 was unevenly distributed in rat DRG prompted an investigation of Oprm1 and Oprd1 to answer whether these analgesic opioid receptors were also distributed unevenly across cell populations. (A) In a wide field view of a DRG stained for Oprm1 and Oprd1, we did not observe marked differences in expression across the field. The gene encoding the mu-opioid receptor (Oprm1) is much more widely expressed than the delta receptor gene (Opd1), and both show a range of expression values. (B) However, this range appeared qualitative smaller than that observed for Trpv1. (C) In order to quantify this further, we used a surface plot to represent intensity over area for Oprm1. (D) When viewed from an angle, this analysis shows many peaks of similar height across the DRG, consistent with the wide expression pattern of Oprm1. This is in contrast to Trpv1, which showed several very high peaks (Figure 2E). (E) The same analysis was also performed for Oprd1, which is expressed in many fewer cells than either Trpv1 or Oprm1. (F) Viewed at an angle, most of these Oprd1 peaks are evident in the same linear axis. In Supplementary Figure 2, we quantified differences in distribution and coefficient of variation in these measurements, showing that Trpv1 had significantly higher coefficient of variation than either Oprm1 or Oprd1.