Nematodes acetylcholine

Isotonic muscle contraction was used to measure the effects of selected nematode FaRPs on the body-wall muscle of H. contortus. AF2 was found to have inhibitory effects on muscle activity and inhibited acetylcholine (ACh) -induced contractions in the worm whereas AF8 had excitatory effects on the muscle and enhanced ACh-induced contractions (Marks et al., 1999a). There were obvious differences in the methodologies used to evaluate the effects of these peptides on Haemonchus muscle compared with those used to examine these peptide effects on Ascaris. How comparable the results are has yet to be determined. 

Nematode neurons (Pre-cambrian) Na+/K+, Ca2+, acetylcholine glycine Butyrate, GABA Recovery by re-entering synapse... 

Three pyrantel salts (pamoate, embonate and tartrate) are indicated for use in the horse. The pyrimidines are selective agonists at synaptic and extrasynaptic nicotinic acetylcholine receptors on nematode muscle cells, which produce spastic paralysis of the parasites. 

The nervous system in helminths has important differences from that of humans and these differences form the basis of the selective toxicity of most drugs used to treat such infections. For example, nematode muscles have both excitatory and inhibitory neuromuscular junctions. The neurotransmitters are acetylcholine and gamma-aminobutyric acid (GABA), respectively. 

Mellanby, H. (1955) The identification and estimation of acetylcholine in three parasitic nematodes, Ascaris lumbricoides, Litomosoides carinii, and the microfilariae of Dirofilaria repens. Parasitology 45 287-294. 

Culotti, J. G. and Klein, W. L. (1983) Occurrence of muscarinic acetylcholine receptors in wild-type and cholinergic mutants of the nematode Caenorhabditis elegans. J. Neurosci. 3 359-368. 

Lewis, J. A. and Fleming, J. T. (1991) Cloning nematode acetylcholine receptor genes. Abstr. Neurotox 91, p. 8. 

The quaternary ammonium compound PAM has been shown to have nicotinic stimulant properties at autonomic ganglia in the anaesthetised dog [226] and in muscle preparations of the ascaris nematode [227]. PAM was thought to have a curare-like action at concentrations above 6 niM [228] which later was shown to be due to its reducing the presynaptic release of acetylcholine [229]. The non-quatemised oxime, MINA, also has been reported to have anti-nicotinic properties [230]. 

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