Figure 4. Serotonin is essential for induction of fast pumping.

(a) The average fraction of time spent in fast pumping by tph-1 worms at various food concentrations. Empty symbols, no added serotonin; filled symbols, in media supplemented with 5 mM serotonin. Sample sizes are given in Supplementary Table 2. (b) F(r), the fraction of time spent in intervals longer than 1/r, in various food concentrations with no serotonin added to the media (red, green, blue) and in 5 mM serotonin in the absence of bacteria (orange). Dashed lines are the best-fit lines between 100 pumps per min and 250 pumps per min. (c) The average fraction of time spent in fast pumping by worms in which serotonin production or secretion has been perturbed in all or some of the serotonergic neurons (blue and grey) and in worms in which serotonergic neurons had been ablated by reconstituted caspase-3 (red). Food was supplied at OD₆₀₀=3. Error bars as in Fig. 2.