Fig. 5.

The increases in both contraction amplitude and frequency, as well as the decrease in contraction duration, induced by H. americanus calcitonin-like diuretic hormone (Homam-CLDH) are dose dependent. Pooled data from preparations exposed to concentrations of Homam-CLDH ranging from 10^–8 to 10^–11 mol l^–1 showed that cycle frequency increased (A), contraction amplitude increased (B) and burst duration decreased (C), with larger effects at higher concentrations. Threshold, defined as the concentration at which per cent change is significantly different from zero, was less than 10^–10 mol l^–1 for all parameters. Specifically, threshold for the increase in contraction amplitude was between 10^–10 and 10^–11 mol l^–1; threshold for both the increase in cycle frequency and the decrease in burst duration was less than 10^–11 mol l^–1. *Significantly different from zero, one-sample, 2-tailed t-test, P<0.05, N=10. Error bars represent standard errors.