Physiological and biochemical study of peptides and hormones which are active in the cardio vascular and reproductive systems of octopus

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1.Octopus cardioactive peptidesTwo peptides that showed both positive chronotropic and inotropic effects on the heart were isolated from brain extracts of Octopus minor using the systemic heart bioassay. The presence of the peptides in the systemic heart was confirmed by TOF-MS and tandem MS analysis. These peptides might be involved in excitatory control of the octopus cardiovascular system as neuropeptides and/or neurohormones.2.Octopus gonadtropin-reieasing hormone (GnRH)-like peptideA peptide with structural features similar to vertebrate GnRHs was isolated from brains of Octopus vulgaris. This peptide showed luteinizing hormone-releasing activity in quail anterior pituitary cells. The RT-PCR transcripts were expressed in the supraoesophageal and suboesophageal brains, peduncle complex, and optic gland. Immunoreactive neuronal cell bodies and fibers were observed in the subpedunculate lobe that controls the optic-gland activity. Optic gland nerves and glandular cells in the gland were immunostained. The isolated peptide may be Octopus GnRH that contributes to octopus reproduction not only as a neurohormone but also as an endocrine hormone.3.A second member of vasopressin/oxytocin (VP/OT)-superfamily peptides in OctopusOctocin was isolated as a second member of VP/UT-superfamily peptides in addition to the already known peptide, cephalotocin. The precursors of octocin and cephalotocin were highly similar to each other. The structural organizations were typical of the known VP/UT precursors : a signal sequence, a nonapeptide, and a neurophysin domain. The expressions of both peptides were different in the brain, namely, octocin was expressed mainly in the supraoesophageal lobes, which are concerned with voluntary movements, in contrast, and cephalotocin was expressed in the vasomotor lobes that send axons to the vena cava neurosecretory system.