TrkA- and TRPM8 expression and morphology of DRG neurons in culture. (A&B) Small diameter DRG neurons in culture express the TrkA receptor and TRPM8 channels. Immunofluoresence images of 12 hr DRG cultures stained with (A) an anti-TrkA (green), (B) an anti-TRPM8 (green) antibodies, and DAPI (blue). Analysis of somatic diameters displaying immunoreactivity (closed circles) for (C) TrkA and (D) TRPM8 show a significant bias of TrkA and TRPM8 immunoreactivity (closed circles) in smaller neurons (<15 μm) compared with TrkA and TRPM8 negative neurons (open circles). (n = 326 and 223 cells counted respectively, scale bar is 20 μm). (E) TRPM8 immunoreactivity in culture. DRG neurons displaying effusive growth cone morphologies (suitable of calcium imaging experiments) were TRPM8 positive (scale bar is 50 μm).