Fig. 4.

Homarus americanus calcitonin-like diuretic hormone (Homam-CLDH) increased heartbeat frequency and contraction amplitude, and decreased duration of heart contractions. (A) Contraction frequency is shown graphically with time, on the same slow time scale as the recording of contraction force. Homam-CLDH (10^–8 mol l^–1) was applied during the time indicated by the bar over the recordings. Both frequency and amplitude increased, then gradually returned to baseline values. (B) Higher speed recordings taken from the regions demarcated in A, showing the increases in amplitude and frequency and the decreased duration of the heartbeats.