Peptidergic Modulation of Cardiac Performance in Isolated Hearts from the Shore CrabCarcinus maenas

Abstract

The present study examined the effects of two peptide hormones on rate, pressures, and flow generated by isolated in situ crustacean hearts. Saline, pumped by spontaneous contractions, was collected through a cannula attached to the sternal artery. Cardiac flow was measured directly with an electromagnetic low probe, while arterial and ventricular pressures were recorded with pressure transducers. Crustacean cardioactive peptide (CCAP), known to be present in the pericardial organs of Carcinus, increased cardiac output mainly by increasing heart rate. On average, CCAP caused a modest increase in stroke volume. Proctolin, another peptide found in the pericardial organs, also increased cardiac output, but generally elicited large changes in the stroke volume. Proctolin also increased heart rate, but to a lesser extent than did CCAP. Both peptides increased ventricular pressure, stroke work, and cardiac power. Mean effective dose ($ED_{50}$) values associated with the effects on heart rate were approximately...