Adrenomedullin-like immunoreactivity in the nervous system of the starfish Marthasterias glacialis.

The nervous system of the starfish Marthasterias glacialis was investigated immunocytochemically using an antiserum specific for adrenomedullin (AM), a new regulatory peptide. Immunoreactivity was only found in nerves of the basiepithelial plexus of cardiac and pyloric stomachs and pyloric caeca, while the radial nerve cords and the other digestive organs were negative. The strongest AM-like immunoreactivity was located in the current-producing areas of the cardiac stomach. The distribution of this peptide suggests different functions in echinoderms involving regulation of muscle movement and neurotransmission. The presence of an AM-like substance in echinoderms points to an early phylogenetic origin for this regulatory system.