Cardiac and ventilatory responses to stress and to neurohormonal modulators by the shore crab, Carcinus maenas

Abstract

1. Crabs respond to handling and surgery with stress-like increases in heart rate (36%) and ventilatory rate (233%). The ventilatory responses last longer than heart responses, often exceeding 2 hr. 2. Neurohormones known to be released from the pericardial organs were injected into crabs. The biogenic amines 5-hydroxytryptamine (5-HT), octopamine and dopamine, and the peptide proctolin each produced small increases in heart and dramatic increases in ventilatory rates. These dose-dependent responses were of long duration. 3. High concentrations of 5-HT and proctolin each produced a short 5 min period of cardiac and ventilatory arrest immediately following the injection. 4. High concentrations of octopamine stimulated a moderate increase in the occurrence of reversed direction ventilation sessions whereas 5-HT and dopamine did not.