Parasitology

Research Article

Pharmacological profile of the 5-hydroxytryptamine receptor of Fasciola hepatica body wall muscle

E. A. Tembea1, L. Holden-Dyea1 c1, S. W. G. Smitha2, P. A. M. Jacquesa2 and R. J. Walkera1

a1 Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, Southampton SO9 3TU

a2 Cambridge Animal and Public Health Ltd, Chesterford Park Research Station, Saffron Walden, Essex

Abstract

5-HT is a candidate for the excitatory transmitter at the neuromuscular junction in trematodes including Fasciola hepatica. This study has determined the response of a muscle strip preparation from Fasciola hepatica to 5-HT and a range of agonists that distinguish between the vertebrate receptor 5-HT subtypes. 5-HT increased the resting tone and the rhythmic activity of the muscle strip. Of the 19 compounds tested, only 10 had an effect similar to 5-HT and all but 2 of these were tryptamine compounds. 5-HT was more potent than tryptamine whilst 4-OH-tryptamine had no effect, suggesting that the response is mediated by a 5-HT rather than a tryptamine receptor. 5-Fluorotryptamine and 5-carboxyamidotryptamine were the most potent agonists. 8-OH-DPAT also mimicked the effect of 5-HT, though less potently. Assuming that these agents elicit their response through a common receptor, this suggests the presence of a 5-HT receptor with similar properties in terms of agonist recognition as the vertebrate 5-HT1 class of receptor involved in controlling Fasciola muscle motility.

(Received February 22 1992)

(Revised June 02 1992)

(Accepted June 02 1992)

Correspondence:

c1 Dr L. Holden-Dye, Department of Physiology and Pharmacology, University of Southampton, Bassett Crescent East, Southampton SO9 3TU

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