Evidence for CRF-like and kinin-like peptides as neurohormones in the blood-feeding bug, Rhodnius prolixus.
In Rhodnius prolixus, the rapid post-feeding diuresis is under neurohormonal control. While serotonin has been demonstrated to be a diuretic neurohormone [J Exp Biol 156 (1991) 557], a peptide is also known to be involved. Previously, we have demonstrated the presence of corticotropin releasing factor (CRF)-like and kinin-like peptides in the central nervous system (CNS) of 5th instar Rhodnius [J Exp Biol 202 (1999) 2017; Peptides 22 (2001) 161]. These peptides are present in neurohemal sites of the corpus cardiacum and are co-localized in neurohemal sites on abdominal nerves. While various CRF-like peptides have been demonstrated to increase Rhodnius Malpighian tubule secretion the kinin-like peptides do not [Peptides 23 (2002) 671]. The kinin-like peptides do however, increase hindgut contraction which may contribute to the rapid post feeding diuresis by the mixing of hemolymph and/or hindgut contents and the removal of wastes. The presence of these peptides in neurohemal sites suggests that they could be released into the hemolymph and act as neurohormones. We have used immunohistochemical techniques and radioimmunoassay (RIA) to demonstrate qualitative and quantitative changes of CRF-like and kinin-like peptides in the CNS associated with feeding. As well we have examined Malpighian tubule secretion in response to assays of hemolymph from unfed and fed insects. Hemolymph was also partially purified by Sep-Pak and HPLC and the fractions assayed for kinin-like immunoreactivity and the ability to stimulate Malpighian tubule secretion. The results suggest that both kinin-like and CRF-like peptides are neurohormones in Rhodnius, released in response to feeding.
Te Brugge
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Department of Zoology, University of Toronto, 25 Harbord Street, Ont., Canada M5S-3G5. vtebrugg@utm.utoronto.ca
Orchard
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D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003346:Corticotropin-Releasing Hormone / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D006458:Hemolymph / Q000378:metabolism; D007150:Immunohistochemistry; D007705:Kinins / Q000502:physiology*; D010455:Peptides / Q000737:chemistry / Q000502:physiology*; D012239:Rhodnius / Q000502:physiology*
D007705:Kinins; D010455:Peptides; D003346:Corticotropin-Releasing Hormone