Flight and running induce elevated levels of FMRFamide-related peptides in the haemolymph of the cockroach, Periplaneta americana (L.)

Abstract

The appearance of FMRFamide-related peptides (FaRPs) in the haemolymph of the cockroach, Periplaneta americana (L.), during flight or running/righting behaviour was investigated using radioimmunoassay and reverse phase-HPLC. Both flight and running/righting behaviours caused an increase in the level of FaRPs measured in the haemolymph within the first minute of activity. Elevated levels (up to 18 times greater than control levels) persisted as long as animals continued the enforced activity (tested up to 15 min). After cessation of activity, levels of FaRPs in the haemolymph decreased to near-control levels in about 8–10 min. RP-HPLC indicated that FaRPs found in the haemolymph may have been released from thoracic ganglia or associated neurohaemal tissue. It is suggested that FaRPs released into the haemolymph during physical activity may play a role in modulating the contraction characteristics of heart and/or skeletal muscle.