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The effect of the nematode peptides SDPNFLRFamide (PF1) and SADPNFLRFamide (PF2) on synaptic transmission in the parasitic nematode Ascaris suum

Published online by Cambridge University Press:  06 April 2009

L. Holden-Dye ,
C. J. Franks ,
R. G. Williams  and
R. J. Walker
L. Holden-Dye
Affiliation:
Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, Southampton SO16 7PX
C. J. Franks
Affiliation:
Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, Southampton SO16 7PX
R. G. Williams
Affiliation:
Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, Southampton SO16 7PX
R. J. Walker
Affiliation:
Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, Southampton SO16 7PX
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Summary

The action of two peptides isolated from the nematode Panagrellus redivivus, PF1 (SDPNFLRFamide) and PF2 (SADPNFLRFamide) have been studied on synaptic transmission in the motornervous system of the parasitic nematode Ascaris suum. Intracellular recordings were made from Ascaris somatic muscle cells and excitatory junction potentials (EJPs) elicited by stimulation of the ventral nerve cord. The EJPs were cholinergic as they were blocked by the Ascaris nicotinic receptor antagonist, benzoquinonium. PF1 caused a slow hyperpolarization, similar to the action of this peptide first reported by Bowman, Geary & Thompson (1990) and further characterized by Franks et al. (1994). The hyper-polarization was accompanied by a marked decrease in the amplitude of the EJPs with an EC50 of 311 ± 30 nM (n = 5). This inhibition is unlikely to be due to a post-synaptic site of action of the peptide as the muscle cell input conductance was not significantly altered by PF1 and furthermore the response to bath-applied acetylcholine was not inhibited by PF1 at concentrations up to 10μM (n = 6). PF2 also inhibited the EJPs in a similar manner to PF1. These studies indicate that both of the peptides isolated from the free-living nematode Panagrellus redivivus have biological activity in the parasitic nematode Ascaris suum. PF1 and PF2 have inhibitory actions in contrast to the predominantly excitatory actions of the Ascaris endogenous peptides AF1 (KNEFIRFamide) and AF2 (KHEYLRFamide). The potent actions of the Panagrellus neuropeptides PF1 and PF2 in Ascaris suggest that peptides with a similar or identical sequence may also occur in Ascarisand have an inhibitory role in the motornervous system.

Keywords

AscarisneuropeptidenematodeFMRFamideelectrophysiology
Type
Research Article
Information
Parasitology , Volume 110 , Issue 4 , May 1995 , pp. 449 - 455
Copyright
Copyright © Cambridge University Press 1995

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