Fig. 6. Responsiveness of the bitter-sensitive taste cell in epipharyngeal and lateral sensilla to 50 mmol l–1 salicin, both before (i.e. 0 h) and after (i.e. 24 or 48 h) exposure to the control or 157 mmol kg–1 salicin diet. To determine whether the responsiveness of each class of bitter-sensitive taste cell changed significantly over the exposure period, we calculated the percentage of initial response [i.e. (number of spikes s–1 after exposure period/number of spikes s–1 before exposure period)x100]. These calculations were based on the initial 1 s of the response (median responses ± median absolute deviation). The number of caterpillars tested in each treatment group was as follows: exposed to control diet for 24 h (N=10) or 48 h (N=9); exposed to salicin diet for 24 h (N=10) or 48 h (N=9). For each caterpillar, we recorded from the same lateral and epipharyngeal sensillum both before and after the exposure period. We compared the medians within each panel with an expected null model of 100 % (broken line) using a one-sample Wilcoxon matched-pairs signed-rank test (*P<0.05). We also present representative neural responses of an epipharyngeal (E,F) and lateral (G,H) sensillum to 50 mmol l–1 salicin (in 0.1 mol l–1 KCl) both before and after 24 h of exposure to the control or salicin diet. In all traces, a single bitter-sensitive taste cell is firing at a consistent and relatively rapid rate, whereas a salt-sensitive taste cell is firing more slowly and irregularly (in response to the electrolyte); action potentials from the latter taste cell are marked with an arrowhead. Each trace displays the initial 250 ms of the neural response.
