Immunohistochemistry confirms depletion of MOR+ neurons by dermorphin-saporin microinjection to the RVM. A). Representative images illustrate MOR+ expression in dermorphin-saporin and saline control animals (approximately −10.5 mm from Bregma). Depletion of MOR+ cells can be observed in the bilaterally injected dermorphin-saporin (DS, 3pmole/96 ng) animal. Scale bar indicates 200 μm. Nucleus raphe magnus (NRM) and nucleus reticularis gigantocellularis (GiA), components of the RVM are shown. B). Cell counts indicate a significant decrease in MOR+ cell number in animals treated with 1.5pmole dermorphin-saporin (DS). Cell counts were calculated as the sum of the top five sections per animal, and data shown here as mean ± SEM per group. n = 3 – 4, *p = 0.022, independent samples t-test. C). Representative single plane confocal images of MOR immunohistochemistry in the 1.5pmole dermorphin-saporin group and saline control. Double labelling with NeuN indicated that although many MOR+ neurons are depleted at this dose, some surviving MOR- neurons remain in the region, indicated by white arrows. Scale bars indicate 25 μm.