Table 1. Main neuropeptides of vertebrates and orthologs in helminths.

Neuropeptide family	Vertebrate tissue expression	Presence in helminths	Function	Receptors in helminths	References
Corticotropin-releasing hormones	Hypothalamus	C. elegans	Regulate locomotor activities	C. elegans	[15]
Somatostatin	Hypothalamus, pancreas	Unknown	Regulate immune system	C. elegans	[15–17]
Neuropeptide Y	Brain, intestine, immune	C. elegans	Parasite feeding Host immune regulatory	C. elegans	[18–20]
QRFP peptides	Hypothalamus	Echinococcus Ascaris	Parasite motility	Unknown	[21,22]
Oxytocin/vasopressin	Pituitary	C. elegans	Reproductive behaviour Associative learning	C. elegans	[23,24]
Opioid peptides	Brain	S. mansoni C. elegans	Regulate immune system Regulate feeding behaviour	S. mansoni	[24–26,28]
Glucagon/secretin	Brain and pancreas	Unknown	Metabolism Immune respinse	Unknown	[27]
Galanin family	Brain	C. elegans	Regulate foraging behaviour	C. elegans	[29]
Substance P-like tachykinins	Brain	C. elegans	Promotion of aggression, sexual activity and fecundity	C. elegans	[30]
Serotonin	Brain/gut	C. elegans	Feeding, reproduction	F. hepatica	[114]
Neuropeptide F	Brain/heart	S. mansoni, F. hepatica	Myoexcitation	Unknown	[31]
Insulin-like peptides	Brain	T. solium, Echinococcus multilocularis	Glucose and glycogen metabolism	T. solium	[32,115]