Fig. 7. Quantitative summary of effects of guanylate cyclase and phosphodiesterase inhibitors [ODQ (1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one) and zaprinast, respectively] on peristalsis (A) and their representative effects on the behaviour of whole colonies (B,C). (A) Histogram showing the actions of ODQ and zaprinast on peristalsis, as well as their interactions with the effects of other signalling molecules (see Results). Statistical significance: P>0.05 (n.s.), ^*P<0.05 or ^**P<0.01 with the paired t-test. N=6 (ODQ/SNAP), 4 (melatonin/ODQ) and 5 (zaprinast/db cGMP/IBMX). (B) Injection of ODQ in the left half of the colony led to a slightly contracted state and stronger peristalsis (as illustrated by the marginal fold) relative to the control (right) half. (C) Injection of aminoguanidine in the left half of another colony led to a relaxed and quiescent state relative to the control half where robust peristalsis occurs (compare the two pictures of the same colony photographed 30 s apart). Black line indicates the position of the axial canal.