Studies on the nicotinic receptor on the somatic muscle cells of the parasitic nematode Ascaris suum
Studies on the nicotinic receptor on the somatic muscle cells of the parasitic nematode Ascaris suum
The excitatory neurotransmitter at the neuromuscular junction of Ascaris suum is acetylcholine. In this study the pharmacology of the receptor on the somatic muscle cells has been extensively characterised using conventional electrophysiological techniques. Acetylcholine (1-10μM) elicited a depolarisation (8.3±0.5mV; n= 40, to 10μM ACh) and an increase in input conductance of the cell (0.45±0.06μS; n= 40, to 10μM ACh). The agonist profile indicated a nicotinic type of receptor with particular sensitivity to ganglionic agonists. The most potent agonists were HPPT, DMPP and the anthelmintic levamisole. These were all more potent than ACh. Neuromuscular agonists were less potent than ACh, the order of potency being carbachol> nicotine> suberyldicholine> trimethylammonium. Cytisine was a weak agonist at this receptor. Muscarinic agonists were weak agonists at the Ascaris muscle nicotinic receptor (furtrethonium and muscarone) or inactive up to 1mM (methacholine and bethanechol) as was the insecticide NMTHT. Pilocarpine elicited a small hyperpolarisation of the muscle cells indicating the possibility of a population of muscarinic receptors. Two anticholinesterases were investigated. Neostigmine (10-6, 10-5M) potentiated the ACh response, physostigmine (10-5M) inhibited the response to ACh. A number of antagonists were tested on this preparation, IC50s for block of the conductance change to ACh are given in brackets where appropriate. The most potent tested in this study was benzoquinonium (0.29μM). Pancuronium and tubocurarine both inhibited the ACh response in the low micromolar range (3.2μM and 3.1μM respectively) as did atropine (6.7μM). Dihydro-β-erythroidine was inactive up to 100μM.
University of Southampton
1991
Colquhoun, Lorna Mairi
(1991)
Studies on the nicotinic receptor on the somatic muscle cells of the parasitic nematode Ascaris suum.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The excitatory neurotransmitter at the neuromuscular junction of Ascaris suum is acetylcholine. In this study the pharmacology of the receptor on the somatic muscle cells has been extensively characterised using conventional electrophysiological techniques. Acetylcholine (1-10μM) elicited a depolarisation (8.3±0.5mV; n= 40, to 10μM ACh) and an increase in input conductance of the cell (0.45±0.06μS; n= 40, to 10μM ACh). The agonist profile indicated a nicotinic type of receptor with particular sensitivity to ganglionic agonists. The most potent agonists were HPPT, DMPP and the anthelmintic levamisole. These were all more potent than ACh. Neuromuscular agonists were less potent than ACh, the order of potency being carbachol> nicotine> suberyldicholine> trimethylammonium. Cytisine was a weak agonist at this receptor. Muscarinic agonists were weak agonists at the Ascaris muscle nicotinic receptor (furtrethonium and muscarone) or inactive up to 1mM (methacholine and bethanechol) as was the insecticide NMTHT. Pilocarpine elicited a small hyperpolarisation of the muscle cells indicating the possibility of a population of muscarinic receptors. Two anticholinesterases were investigated. Neostigmine (10-6, 10-5M) potentiated the ACh response, physostigmine (10-5M) inhibited the response to ACh. A number of antagonists were tested on this preparation, IC50s for block of the conductance change to ACh are given in brackets where appropriate. The most potent tested in this study was benzoquinonium (0.29μM). Pancuronium and tubocurarine both inhibited the ACh response in the low micromolar range (3.2μM and 3.1μM respectively) as did atropine (6.7μM). Dihydro-β-erythroidine was inactive up to 100μM.
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Published date: 1991
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Local EPrints ID: 460918
URI: http://eprints.soton.ac.uk/id/eprint/460918
PURE UUID: d0335671-08a0-440d-a34f-81b56d31ae18
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Date deposited: 04 Jul 2022 18:32
Last modified: 04 Jul 2022 18:32
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Author:
Lorna Mairi Colquhoun
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