2.8.2 Signal intensity of MOP immunoreactivity in the spinal cord
For measurements of MOP immunoreactivity, the spinal cord was divided along the dorsoventral axis and the signal intensity of each section was measured using ImageJ (version 1.52v, NIH). Superficial and deep lamina sections of Oprm1 cKO and WT mice (3 per group) were quantified by using a global background threshold and compared by their total integrated density (area×mean gray value).