Distribution, activity and evidence for the release of an anti-diuretic peptide in the kissing bug Rhodnius prolixus

摘要

In the haematophagous insect Rhodnius prolixus, diuresis is accomplished through the combined actions of peptidergic diuretic hormones and 5-HT released from neurohaernal sites on the abdominal nerves. Preliminary work on anti-diuresis in this blood-feeder, previously believed to occur through a decrease in the levels of the diuretic factors, indicates that an anti-diuretic hormone, with properties similar to CAP2b (pELYAFPRV amide; recently renamed Mas-CAPA-1), might also be present in R. prolixus. Here, we present evidence from immunohistochemical analysis that suggests a PRXamide-like neuropeptide may be released from the abdominal neurohaernal sites beginning 3-4h following feeding; a time that coincides with the cessation of diuresis. We also show evidence for an endogenous factor, isolated from the central nervous system using reversed-phase high performance liquid chromatography, which mimics the effects of Mas-CAPA-1. Specifically, this endogenous antidiuretic factor inhibits rates of 5-HT-stimulated secretion in a dose-dependent manner and elevates intracellular cGMP levels of Malpighian tubules stimulated with 5-HT.