Immuno-labeling for TRPM8 at the cold thermoreceptor recording site where the electrical activity shown in Fig 1 was recorded.

A, fluoro-gold fluorescence within the white dotted circle identifies the approximate location of the recording site. B, bright-field image showing within the white dotted circle the mark left on the corneal surface by the rim of the recording electrode. C, all axons in the field of view were revealed by β-tubulin III-IR (green). D, a TRPM8-IR (red) nerve terminal was located at the recording site. In C and D, the white dotted circle approximates dimensions of the electrode tip at the recording site revealed in B. The scale bar in A–D = 50 μm. E and F, show a 3-dimensional reconstruction of the TRPM8-IR nerve terminal viewed from the front (E) and side (F). Panel F shows an orthogonal projection of the image shown in D. In C–F, the asterisk marks the site where the parent axon of the TRPM8-IR nerve terminal enters into the epithelium through Bowman’s membrane. The dashed lines in F approximate the area occupied by the corneal epithelium.