Extended Data Figure 6: ON and OFF responses of fast tPNs are not limited to a defined range of absolute temperature.
To better understand the nature of ON and OFF responses, we tested whether the dynamic activity of fast-adapting cells was limited to a defined range of absolute temperatures by delivering defined heating and cooling stimuli from a range of baseline temperatures. a, ON responses from cold (purple traces) and hot (green traces) cells recorded from a 25 °C baseline and from a higher (29 °C) or lower (20 °C) baseline, respectively (shown are representative single stimuli and corresponding response traces recorded from cell bodies). b, c, The activity of fast tPNs is not restricted to a specific temperature band as evident by plotting the absolute temperature corresponding to response onset (see arrows in a) against the baseline temperature for fast-adapting cold (b) and fast-adapting hot (c) cells, challenged with a range of hot and cold stimuli (ΔT 2–7° C; cooling ΔT = −4.7 ± 1.9 °C, heating ΔT = 4.6 ± 2 °C, mean ± s.d.; n > 10 cells/>10 animals per cell type). In b, c, filled purple and green dots represent ON responses while empty circles represent OFF responses. Owing to their specific delay, the OFF responses of cold cells start at the very end of a hot stimulus (that is, when the temperature has nearly returned to baseline Tonset – Tbaseline = 0.68 ± 0.43 °C, mean ± s.d.); in contrast, hot cells respond at or near the start of the heating phase that follows a cold stimulus (see below) and, as a result, systematically at a lower temperature than baseline (Tonset – Tbaseline = −2.97 ± 1.15 °C, mean ± s.d.; note that this value is significantly different than the one calculated for cold cells, P < 0.001, t-test). d–h, Fast-adapting hot cells innervating the lateral pathway display OFF responses whose delay varies by cell. d, e, A pair of adjacent hot-activated (green arrow and trace) and cold-activated (purple arrow and trace) tPNs innervating the lateral pathway (3D reconstruction in d, cell bodies in e; same cells and colour coding as in main Fig. 3). f, The cold-activated tPN responded to cooling stimuli with a rapid ON transient. The hot-activated cell in this pair displayed a calcium transient that was not delayed; that is, started immediately with the heating phase that followed the cooling stimulus (light green trace). g, h, In contrast, a different fast hot cell type in the same cluster (dark green circle and trace) displayed a delayed response (arrowhead), similar to the delayed OFF response reported for cold-activated tPNs at the end of a heating stimulus (see Fig. 3). Scale bars in e and g, 5 μm.
