ABSTRACT
NGIWYamide (Asn-Gly-Ile-Trp-Tyr-NH2), a recently isolated neuropeptide from the sea cucumber, Apostichopus japonicus, was tested on the tube foot of the starfish, Asterina pectinifera. NGIWYamide of 10-6-10-4 M caused contraction of the isolated tube foot whereas 10-7 M did not elicit any response. NGIWYamide-like immunoreactivity (NGIWYa-LI) was investigated using Asterina pectinifera and Linckia multifora with specific antiserum raised against NGIWYamide. Our studies showed the NGIWYa-LI in the radial nerve cord (RNC), the marginal nerve and the tube foot. Both ectoneural and hyponeural parts of RNC showed the presence of NGIWYa-LI. Immunoreactive cell bodies were found in the both parts of the RNC. Immunoreactive fibers were evident in the hyponeural part of the RNC. Uniform labeling in the basal region of the ectoneural part suggested that some nerve fibers in this part of RNC are also immunoreactive. In the tube foot, NGIWYa-LI was found in the sub-epithelial nerve plexus and in the basal nerve ring. These results suggest that NGIWYamide is a neurotransmitter or a neuromodulator of the starfish and involved in the contraction of the muscle of the tube foot.
