Typical double immunofluorescence staining of transient receptor potential melastatin 8 (TRPM8) and neurofilament 200 (NF200) in the rat dorsal root ganglion (DRG) of streptozotocin (STZ)-induced diabetic rats. Pretreatment with nefopam (30 mg/kg) was performed intraperitoneally 30 min prior to an intraperitoneal injection of STZ (60 mg/kg). Four weeks after the final drug treatment, L5 DRG samples were immunostained with TRPM8 and neurofilament 200 (NF200), a marker of myelinated neurons. The colocalization of TRPM8 was visualized in a merged image.