Insect tachykinin-related neuropeptides: Developmental changes in expression of callitachykinin isoforms in the central nervous system and intestine of the blowfly,Calliphora vomitoria

Abstract

We have analyzed the relative distribution of tachykinin-related peptides (TRPs) in extracts of adult brains, thoracico-abdominal ganglia, and midguts and of the larval central nervous system of the blowfly Calliphora vomitoria using high performance liquid chromatography (HPLC) in combination with radioimmunoassay (RIA). The RIA employed antisera to the insect TRPs, locustatachykinin I (LomTK I) and callitachykinin II (CavTK II). For identification of the two known blowfly tachykinins we monitored the retention times of synthetic CavTK I and CAVTK II as a reference. With the CavTK II antiserum, all assayed tissues displayed two immunoreactive HPLC fractions with exactly the same retention times as synthetic CavTK I and CavTK II, respectively. An additional immunoreactive fraction eluting earlier than the reference peptides was detected in the adult midgut extract. When assaying the HPLC fractions with antiserum to LomTK I, we obtained the same patterns of immunoreactivity except that now the early eluting material was detectable in all the adult extracts. In addition, in the larval central nervous system, a third major immunoreactive component was displayed using the LomTK RIA and a fourth detected with the CavTK II RIA. We conclude that CavTK I and II are present at a ratio of about 1:1 in all assayed tissues and that two or three additional unidentified tatchykinin-immunoreactive peptides may exist. One of these was seen in the adult tissues; the others appear to be specific for the larval central nervous system (CNS). The RIA was also utilized to determine the total amount of CavTK-immunoreactive material in adult brain, thoracic-abdominal ganglia, and midgut as well as in larval CNS and intestine. The adult CNS contained about seven times more CavTK-immunoreactive material than the larval CNS, and the adult midgut contained 15 times more than the larval intestine. Correlated with these RIA results, many fewer CavTK immunoreactive endocrine cells were labeled in the larval midgut and fewer neurons in the larval CNS than in the Corresponding tissues of adults. Arch. Insect Biochem. Physiol. 34:475–491, 1997. © 1997 Wiley-Liss, Inc.