Structure, distribution, and biological activity of novel members of the allatostatin family in the crayfish Orconectes limosus.

ABSTRACT

In the central and peripheral nervous system of the crayfish, Orconectes limosus, neuropeptides immunoreactive to an antiserum against allatostatin I (= Dipstatin 7) of the cockroach Diploptera punctata have been detected by immunocytochemistry and a sensitive enzyme immunoassay. Abundant immunoreactivity occurs throughout the central nervous system in distinct interneurons and neurosecretory cells. The latter have terminals in well-known neurohemal organs, such as the sinus gland, the pericardial organs, and the perineural sheath of the ventral nerve cord. Nervous tissue extracts were separated by reverse-phase high-performance liquid chromatography and fractions were monitored in the enzyme immunoassay. Three of several immunopositive fractions have been purified and identified by mass spectroscopy and microsequencing as AGPYAFGL-NH2, SAGPYAFGL-NH2, and PRVYGFGL-NH2. The first peptide is identical to carcinustatin 8 previously identified in the crab Carcinus maenas. The others are novel and are designated orcostatin I and orcostatin II, respectively. All three peptides exert dramatic inhibitory effects on contractions of the crayfish hindgut. Carcinustatin 8 also inhibits induced contractions of the cockroach hindgut. Furthermore, this peptide reduces the cycle frequency of the pyloric rhythms generated by the stomatogastric nervous system of two decapod species in vitro. These crayfish allatostatin-like peptides are the first native crustacean peptides with demonstrated inhibitory actions on hindgut muscles and the pyloric rhythm of the stomatogastric ganglion.