IDENTIFICATION, TISSUE LOCALIZATION AND PHYSIOLOGICAL EFFECT IN-VITROOF A NEUROENDOCRINE PEPTIDE IDENTICAL TO A DIPTERAN LEU-CALLATOSTATININ THE CODLING MOTH CYDIA-POMONELLA (TORTRICIDAE, LEPIDOPTERA)

A neuroendocrine peptide of the Leu-callatostatin family, LPVYNFGL-NH2 , has been isolated from tissue extracts of 5th instar larvae of the c odling moth, Cydia pomonella (Lepidoptera). It is identical to a pepti de previously isolated from the blowfly, Calliphora vomitoria (Diptera ). The distribution of this peptide within the tissues of C. pomonella has been mapped by immunocytochemistry using antisera raised against LPVYNFGL-NH2. Midgut endocrine cells contain Leu-callatostatin immunor eactivity, as do several paired Leu-callatostatin neurones in the brai n and ventral nerve cord. Within the visceral nervous system, the fron tal ganglion contains four Leu-callatostatin neurones. Axons from thes e cells combine with others originating from neurones in the brain and project within the nervi cardiostomatogastrici to innervate the tissu es of the foregut. In particular, the oesophageal valve has a prominen t ring of Leu-callatostatin-immunoreactive fibres. The synthetic pepti de, LPVYNFGL-NH2, has a potent reversible inhibitory effect in vitro o n all visible forms of spontaneous contractile activity of the foregut , including closure of the oesophageal valve. Complete myoinhibition i s observed at peptide concentrations from 10(-10) to 10(-16) M. These results, in conjunction with the results of similar studies on cockroa ches, crickets and flies, suggest that the Leu-callatostatins are a ub iquitous family of insect neuroendocrine peptides with an important ro le in the control of gut motility.