Localisation of serotonin and dopamine in Haemonchus contortus

[Display omitted] ► The localisation of serotonin and dopamine neurotransmitters in Haemonchus contortus was mapped using immuno-staining. ► Serotonin localised in amphidial and pharyngeal neurons in both adult female and male worms, and was also found in ray sensory neurons and a few ventral cord motor neurons in males. ► Dopamine was detected only in the neuronal commissures linking the lateral and sub-lateral nerve cords in both sexes. ► This study provides new insights into the neuronal anatomy and aminergic nervous system in H. contortus. Serotonin and dopamine play important roles in the biology of nematodes where they exert their effect on feeding, locomotion and reproductive behavior. Haemonchus contortus, a parasitic nematode which infects small ruminants, is responsible for considerable economic losses in agriculture. In the current study we have mapped the localisation of these two neurotransmitters in this parasite using immuno-staining. Serotonin localised in amphidial and pharyngeal neurons in both adult female and male worms. Serotonin was also found in ray sensory neurons as well as in a few ventral cord motor neurons exclusively in adult males. Surprisingly, dopamine was only detected in the neuronal commissures linking the lateral and sub-lateral nerve cords in both sexes. We also studied the effect of these two molecules on female adult worms in vitro. Serotonin mainly inhibited movement whereas dopamine had a profound paralytic effect on the mid-body of the worms.