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An overview of neurotransmitters of helminth parasites
... These observations suggest that two types of receptors -adrenergic and dopaminergic -in P. cervi, and their activities, were antagonized by their classical blockers. Similarly, the presence of serotonergic, cholinergic and peptidergic neurons have been demonstrated immunocytochemically in S. mansoni (Pax et al., 1984;Gustafsson, 1987), and serotonergic, cholinergic and adrenergic receptors have been shown functionally in G. crumenifer (Verma et al., 2007(Verma et al., , 2009(Verma et al., , 2010. The present investigation also suggests the involvement of adrenergic and dopaminergic receptors in the muscle of P. cervi. ...
The neuromuscular system of helminths is an important area for target identification and drug development. Many anthelmintics, namely ivermectin, levamisole, piperazine, pyrantel, praziquantel and organophosphates, produce paralysis of helminths by affecting their neuromuscular systems. The neuromuscular system of helminths is also an important area of research to identify some of the important differences between the neuromuscular physiology of helminths and mammals. The identification of differences would help in developing newer target-specific, safe and effective anthelmintics. The present study was carried out to investigate the effects of different adrenergic neurotransmitters (epinephrine, norepinephrine, dopamine, l-dopa) and their antagonists (propranolol and haloperidol) on the spontaneous muscular activity of isometrically mounted Paramphistomum cervi.
... Neurotransmitters are the endogenous substances released selectively from nerve terminals at synapses and neuromuscular junctions in mammals and helminth parasites. In helminth parasites, these neurotransmitters regulate muscle contraction and help in the attachment, feeding and reproduction of parasites (Prichard, 2005;Verma et al., 2007). Acetylcholine (ACh) is an endogenous classical neurotransmitter in the neuromuscular system of animals and has been demonstrated functionally and immunocytochemically in both the central and peripheral nervous systems of flatworm parasites (Maule et al., 1990;Pax et al., 1996). ...
Acetylcholine is the major endogenous classical neurotransmitter in the central and peripheral nervous system of trematodes and mammals. This study investigates the effects of cholinergic drugs on muscle activity in the amphistome, Gastrothylax crumenifer. In the present investigation, acetylcholine (10- 7-10- 3 m) did not produce any marked effect, whereas carbachol (10- 7-10- 3 m) elicited a concentration-dependent decrease in amplitude, baseline tension and frequency of contractions as compared to the control. Nicotine (10- 7-10- 3 m) produced a significant decrease in the amplitude and frequency of spontaneous muscular activity in a concentration-dependent manner, as compared to control amplitude (0.5 +/- 0.01 g) and frequency (58.5 +/- 3.45 per 5 min). However, the baseline tension was also reduced significantly by 10- 3 m nicotine. Atropine (10- 7-10- 3 m) elicited a concentration-dependent increase in amplitude and baseline tension, whereas there was no significant effect on the frequency of the spontaneous contractions of rumen flukes. These observations indicate that G. crumenifer has an inhibitory cholinergic system and that the inhibitory activity of nicotine is more pronounced than that of carbachol or acetylcholine.
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