No abstract

An analysis was made of the effects of 5 neuropeptides on the isolated branchial heart of Sepia oficinalis. There is evidence to suggest that these 5 neuropeptides occur in the neurosecretory system of the vena cava (NSV system) of cephalopods. YGGFMRFamide and oxytocin caused concentration-dependent increases in pressure amplitude in the perfused preparations, with their effects on heart rate being negligible. The molluscan neuropeptide FMRFamide hardly had any effect on the branchial heart beat when applied alone, but it counteracted the positive inotropic actions of noradrenaline. FLRFamide and a-melanotropin had no effect in our system. None of the peptides tested in bioassays on branchial hearts was as efficient as a perfusate obtained from the cephalic vein of Sepia (including the NSV area) that had been stimulated by electrical irritation of the attached visceral nerves. These findings suggest that there may be further neurohormones in the NSV system that are released into the vessel lumen. It is suggested that the branchial hearts of Sepia in vivo are influenced by humoral peptides from the NSV system and that these peptides may act directly on target myocytes or may alter (i.e., potentiate or oppose) the effects of other cardioactive compounds.0 1992 Wiley-Liss, Inc.

No abstract