A study of specific neuropeptide binding sites in parasitic invertebrates

287 A STUDY OF SPECIFIC NEUROPEPTIDE BINDING SITES IN PARASITIC INVERTEBRATES. M.M. MOORE, C. SHAW, T.A. GARDINER, A.G. MAULE & D.W. HALTON Division of Metabolism and Endocrinology, School of Clinical Medicine, School of Biology and Biochemistry,The Queen's University of Belfast, N. Ireland, BT12 6BJ. Neuropeptide F (NPF) is an abundant, ubiquitous peptide found in representative members of the major invertebrate phyla examined to date, including Cnidaria, Platyhelminthes, Annelida, Arthropoda and Mollusca. While NPF was isolated from the mollusc, Aplysia, by means of its potent inhibitory actions on neurones, nothing is at present known of its physiological function in the group (Platyhelminthes), from which it was originally isolated. However, its presence in nerves which innervate muscle and its particular association with the reproductive system suggests a regulatory function in this group. Thus, NPF-controlled mechanisms within parasitic invertebrates represent potential therapeutic targets permitting selective disruption of this peptidergic system. To define the functional role of NPF it is important to identify specific NPFreceptor interactions. To this end, in vitro receptor binding studies and in vitro autoradiograpby employing a radiolabelled NPF ligand have been carried out. Binding was characterised in membrane suspensions prepared from the parasitic cestode, Moniezia expansa,using 125iodinated synthetic NPF (M. expansa). NPF fragments and homologous peptides were employed in displacement studies to further characterise structure/activity relationships. To confirm these results, in vitro autoradiograpby was carded out on sections ofM. expansa, in order to locate any binding sites and map their tissue dism'bution in the parasite. While specific NPF binding sites have been identified in membrane suspensions from M. expansa, their localization within the tissue has proved difficult to define due to positive chemograpby. Various conditions are now being explored to overcome this.

Co-localisation studies o f NADPH-Diaphorase positive and peptidergic neurons in the nervous system o f Ascaris suum. ALISONMONTGOMERY, ZAINABBASCAL,R.G.WILLIAMS, LINDYHOLDEN-DYE, *M.C.THORNDYKE AND RJ.WALKER. Dept. of Phys. & Pharm., University of Southampton, Southampton, SO9 3TU & Dept. of BioL R.H.B~,, Egham, Surrey, TW20 0EX.

A number of studies have described the existence of complex peptidergic neuronal systems within Ascaris. We have recently identified specific neuronal populations which are revealed by NADPH-diaphorase histochemistry suggesting that neurons in this species may also produce nitric oxide. Whole mount preparations of Asearis were processed for routine immunofluorescence using antibodies to either SALMFamide or to calcitonin-gene-related peptide (CGRP). The same preparations were then processed to reveal diaphorase positive neurons using a modification of the method of Hope et. al. (PNAS, 88, 2811-2814, 1991) allowing simultaneous examination of both the immuno- and histo- chemical markers. The peptidergic and diaphorase positive neurons and nerve fibres were widely distributed within the nervous system of this species especially in the ventral and lateral ganglia but it was clear that the diaphorase positive neurons were distinct from peptidergic neurons with few notable exceptions. Thus a large neuron in the lateral ganglion, and a limited number of commissural nerves stain both for diaphorase histochemistry and SALMF-amide-like immunoreactivity (LD. We have, thus far, not been able to demonstrate co-localisation of diaphorase activity and CGRP-LL