Central and peripheral neural mechanisms for control of the tube-like heart in Articulata

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The Australian velvet worm, Euperipatoides kanangrensis was used for neuroanatomy and for localization of serotonin-, and FMRFamide-like immunoreactivity in the innervation of the heart. Serotonin-like immunoreactivity was observed in cell bodies and neuronal processes throughout the central nervous system. FMRFamide-like immunoreactive neural processes were also observed in a variety of peripheral nerves, including nerves to the heart.We have now found another nerve branching off the nerve from the corpus cardiacum and innervating the junctional region of the dorsal vessel in lepidopterous insects (Bombyx mori and Agrius convolvuli). This nerve inhibited retrograde heartbeat when electrical pulses were applied at the rostral cut-stump of the nerve. These results may indicate that the cardiacal nerve contains inhibitory axons to the anterior region of the dorsal vessel.There are four bilateral pairs of the lateral hearts (LHs) in the 10th to 13th body segments in the earth worm Amynthas sp. Discrete excitatory junction potentials (EJPs) in response to electrical stimuli applied to the segmental nerve were recorded from LH muscle cells in a one to one manner with a constant delay. Immunocytochemistry using anti-serotonin antibodies revealed neural processes in the LH had serotonin-like immunoreactivity. These results suggest that serotonin, among the putative neurohormones for the LHs, may be a excitatory neurotransmitter.