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

In the central and peripheral nervous system of the crayfish, Orconectes li mosus, 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 immunoreac tivity occurs throughout the central nervous system in distinct interneuron s and neurosecretory cells, The latter have terminals in well-known neurohe mal organs, such as the sinus gland, the pericardial organs, and the perine ural sheath of the ventral nerve cord. Nervous tissue extracts were separat ed by reverse-phase high-performance liquid chromatography and fractions we re monitored in the enzyme immunoassay. Three of several immunopositive fra ctions have been purified and identified by mass spectroscopy and microsequ encing 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 t he cycle frequency of the pyloric rhythms generated by the stomatogastric n ervous system of two decapod species in vitro. These crayfish allatostatin- like peptides are the first native crustacean peptides with demonstrated in hibitory actions on hindgut muscles and the pyloric rhythm of the stomatoga stric ganglion. (C) 1999 Elsevier Science Inc. All rights reserved.