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Fig. 7. The threshold for pymetrozine action on the femoral chordotonal organ is
10–8 mol l–1. Response of the middle leg
femoral chordotonal organ (fCO) was monitored during ramp-and-hold stimulation
of the receptor apodeme [ordinate; spike counts during elongation (filled
circles) and relaxation (filled squares) ramps, baseline activity subtracted].
Different concentrations of pymetrozine were applied, starting with
10–9 mol l–1 and increasing in steps of
5-fold or 2-fold (abscissa) every 
25 min until stimulus-related responses
had completely vanished. 10–5 mol l–1 was
applied as the final control concentration. Numbers of measurements per data
point (n=N) range from 6 (above-threshold concentrations) to
12 (threshold area). Median values and 25% percentiles are shown. Graph for
relaxation stimuli is offset to the right by 20% for better visibility of
percentiles. Note that calculation of medians from data obtained in several
individuals obscures the fact that in any given animal pymetrozine had an
all-or-none effect, although at slightly different concentrations; for
details, see text.
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