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The effects of the nematode peptide, KHEYLRFamide (AF2), on the somatic musculature of the parasitic nematode Ascaris suum

Published online by Cambridge University Press:  06 April 2009

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

AF2 is an endogenous RFamide-like peptide from the parasitic nematode Ascaris suum. The potent stimulatory effects of this peptide on the somatic musculature of Ascaris strongly suggest that it may have an important role in the motornervous system. Here we have investigated the possibility that AF2 may elicit a stimulatory action on Ascaris muscle by potentiating the actions of the excitatory cholinergic motornervous system either pre-synaptically, post-synaptically or both. In in vitro pharmacological experiments AF2 produced a dose-dependent increase in the frequency and amplitude of spontaneous contractions of Ascaris muscle strip which lasted for more than 1 h after a 3 min application of AF2 (10 nM–10µM; N = 7). In addition, AF2 (100 nM) potentiated the contraction elicited by ACh by 43 ± 9% (P < 0·01; N = 8). In electro-physiological recordings from muscle cells, AF2 (10–100 nM; N = 10) potentiated the amplitude of EJPs (excitatory junction potentials). For 100 nM AF2, the potentiation of the EJP was 218 ± 48% (N = 7; P < 0·01). This effect reversed after a wash of 10 min. AF2 did not potentiate the depolarization of the muscle cell elicited by bath applied ACh. These latter two observations are consistent with a presynaptic action of AF2. AF2 (10–100 nM) generated spontaneous muscle cell action potentials in previously quiescent cells. This effect took more than 1 h to wash out. These observations are discussed in terms of the paralysis of Ascaris that is elicited by AF2.

Keywords

neuropeptideAF2Ascaris.
Type
Research Article
Information
Parasitology , Volume 110 , Issue 3 , April 1995 , pp. 353 - 362
Copyright
Copyright © Cambridge University Press 1995

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