Levels of biogenic amines in larvae and adults of the rat hookworm, Nippostrongylus brasiliensis (Nematoda)

Changes in the levels, expression, and possible roles of serotonin and dopamine during embryonic development in the giant freshwater prawn, Macrobrachium rosenbergii

We investigated the changes in the levels of serotonin (5-HT) and dopamine (DA), and their possible roles during embryonic development of the freshwater prawn, Macrobrachium rosenbergii. The 5-HT and DA concentrations were quantified using high performance liquid chromatography with electrochemical detection (HPLC-ECD). The levels of 5-HT and DA gradually increased from early developing embryos to late developing embryos. The 5-HT concentrations gradually increased from the pale yellow egg to orange egg stages, and reaching a maximum at the black egg stage. DA concentrations were much lower in the early embryos than those of 5-HT (P<0.05), and gradually increased to reach the highest level at the black egg stage. Immunohistochemically, 5-HT was firstly detected in the early embryonic stages, whereas DA developed later than 5-HT. Functionally, 5-HT-treated female prawns at doses of 2.5×10(-5), 2.5×10(-6) and 2.5×10(-7)mol/prawn, produced embryos with significantly shortened lengths of early embryonic stages, whereas DA-treated prawns at all three doses, exerted its effects by significantly lengthening the period of mid-embryonic stage onwards. These results suggest significant involvement of 5-HT and DA in embryonic developmental processes of this species.

Characterization of a novel tyramine-gated chloride channel from Haemonchus contortus

Tyramine (TA), a trace amine, is becoming accepted as a main stream neurotransmitter in invertebrates. Recent evidence indicates that part of the function of TA in nematodes involves a novel receptor (Cel-LGC-55) from the ligand-gated chloride channel class of ionotropic receptors. However, the role of TA or its receptors in the biology of nematode parasites is limited. Haemonchus contortus is a deadly parasitic worm which causes significant economic burden in the production of small ruminants in many parts of the world. In this study, we have cloned and characterized a novel LGCC from H. contortus which we have named Hco-LGC-55. This receptor subunit is a clear orthologue of Cel-LGC-55 and is able to form a homomeric chloride channel that is gated by tyramine, dopamine and octopamine. Semi-quantitative reverse transcription-polymerase chain reaction (sqRT-PCR) shows that this subunit is expressed in all life-cycle stages of the worm, but appears to have reduced mRNA expression in the adult male.

Monoamines in the albumen gland, plasma, and central nervous system of the snail Biomphalaria glabrata during egg-laying

The potential role of selected biogenic monoamines and related compounds in the reproductive physiology of the freshwater snail Biomphalaria glabrata was investigated. Extracts of the albumen gland (AG), plasma, and central nervous system (CNS) were subjected to high pressure liquid chromatography with electrochemical detection (HPLC-ED), and under the extraction and separation conditions employed the following amines were detected: tyrosine, dihydroxyphenylalanine (DOPA), dopamine, and tryptophan in the AG; DOPA, tyrosine, and tryptophan in the plasma; DOPA, tyrosine, dopamine and 5-hydroxytryptamine in the CNS. These compounds were then quantified in individual samples taken from snails known to be in a particular stage of the egg-laying process. AG dopamine levels were highest in snails in the first stage of the reproductive process, when the AG is secreting perivitelline fluid around each fertilized ovum. Significant decreases in AG protein content during the later stages of the egg-laying process were also evident. Plasma tyrosine and DOPA levels were lowest in snails that contained a fully packaged egg mass, while no changes in monoamine content were observed in the CNS. These data provide insights into the role(s) that monoamines, especially catecholamine-related compounds, may play in B. glabrata reproductive physiology.