Dopamine in tissues of the hydrozoan jellyfishPolyorchis penicillatus as revealed by HPLC and GC/MS

Neuronal Synchronization and Bidirectional Activity Spread Explain Efficient Swimming in a Whole-Body Model of Hydrozoan Jellyfish

Aquatic animals need tightly choreographed movements to efficiently navigate through open waters. Radially symmetric animals, like jellyfish, face the additional challenge of having to respond to regionalized sensory stimuli at the margin of their bell with an orchestrated motor response that initiates predation or escape. The nerve net of hydrozoan jellyfish comprises a condensed ring of electrically coupled neurons, that process sensory input and control the motor output. Here, we aim to understand the coupling of neural activity and motor response by developing a biophysical computational model of the swimming-motor-net of a hydrozoan jellyfish and let it control a swimming jellyfish in a fluid simulation. We find that the neuron activity can synchronize while the signal travels around the ring, eventually triggering a bidirectional wave of activation in the muscles. This mechanism explains seemingly contradicting electrophysiological experiments and minimizes muscle contraction time. Hydrodynamical simulations demonstrate that this setup enables symmetric movement even if neural input is highly asymmetric. We hypothesize that the development of this ring structure supports the jet propulsion by which hydrozoan jellyfish swim. These findings show the importance of considering whole body anatomy and movement when investigating neural design.

Catecholaminergic System of Invertebrates: Comparative and Evolutionary Aspects in Comparison With the Octopaminergic System

In this review we examined the catecholaminergic system of invertebrates, starting from protists and getting to chordates. Different techniques used by numerous researchers revealed, in most examined phyla, the presence of catecholamines dopamine, noradrenaline, and adrenaline or of the enzymes involved in their synthesis. The catecholamines are generally linked to the nervous system and they can act as neurotransmitters, neuromodulators, and hormones; moreover they play a very important role as regards the response to a large number of stress situations. Nevertheless, in some invertebrate phyla belonging to Protostoma, the monoamine octopamine is the main biogenic amine. The presence of catecholamines in some protists suggests a role as intracellular or interorganismal signaling molecules and an ancient origin of their synthetic pathways. The catecholamines appear also involved in the regulation of bioluminescence and in the control of larval development and metamorphosis in some marine invertebrate phyla.

Chemical transmission in the sea anemone Nematostella vectensis: A genomic perspective

The sequencing of the starlet sea anemone (Nematostella vectensis) genome provides opportunities to investigate the function and evolution of genes associated with chemical neurotransmission and hormonal signaling. This is of particular interest because sea anemones are anthozoans, the phylogenetically basal cnidarians least changed from the common ancestors of cnidarians and bilaterian animals, and because cnidarians are considered the most basal metazoans possessing a nervous system. This analysis of the genome has yielded 20 orthologues of enzymes and nicotinic receptors associated with cholinergic function, an even larger number of genes encoding enzymes, receptors and transporters for glutamatergic (28) and GABAergic (34) transmission, and two orthologues of purinergic receptors. Numerous genes encoding enzymes (14), receptors (60) and transporters (5) for aminergic transmission were identified, along with four adenosine-like receptors and one nitric oxide synthase. Diverse neuropeptide and hormone families are also represented, mostly with genes encoding prepropeptides and receptors related to varying closeness to RFamide (17) and tachykinin (14), but also galanin (8), gonadotropin-releasing hormones and vasopressin/oxytocin (5), melanocortins (11), insulin-like peptides (5), glycoprotein hormones (7), and uniquely cnidarian peptide families (44). Surprisingly, no muscarinic acetylcholine receptors were identified and a large number of melatonin-related, but not serotonin, orthologues were found. Phylogenetic tree construction and inspection of multiple sequence alignments reveal how evolutionarily and functionally distant chemical transmitter-related proteins are from those of higher metazoans.

Cnidarian chemical neurotransmission, an updated overview

The ultrastructural, histochemical, immunocytochemical, biochemical, molecular, behavioral and physiological evidence for non-peptidergic and peptidergic chemical neurotransmission in the Anthozoa, Hydrozoa, Scyphozoa and Cubozoa is surveyed. With the possible exception of data for the catecholamines and peptides in some animals, the set of cumulative data - the evidence from all methodologies - is incomplete. Taken together, the evidence from all experimental approaches suggests that both classical fast (acetylcholine, glutamate, GABA, glycine) and slow (catecholamines and serotonin) transmitters, as well as neuropeptides, are involved in cnidarian neurotransmission. Ultrastructural evidence for peptidergic, serotonergic, and catecholaminergic synaptic localization is available, but the presence of clear and dense-cored synaptic vesicles also suggests both fast and slow classical transmission. Immunocytochemical studies, in general, reveal a continuous, non-localized distribution of neuropeptides, suggesting a neuromodulatory role for them. Immunocytochemical and biochemical studies indicate the presence of glutamate, GABA, serotonin, catecholamines (and/or their receptors), RFamides, nitric oxide and eicosanoids in cnidarian neurons and tissues. Gene sequences for peptidergic preprohormones have been reported; putative gene homologies to receptor proteins for vertebrate transmitters have been found in Hydra. Behavioral and physiological studies implicate classical transmitters, neuropeptides, eicosanoids and nitric oxide in the coordination of the neuroeffector systems.

A new G protein-coupled receptor from a primitive metazoan shows homology with vertebrate aminergic receptors and displays constitutive activity in mammalian cells

Biogenic amine receptors mediate wide-ranging hormonal and modulatory functions in vertebrates, but are largely unknown in primitive invertebrates. In a representative of the most basal multicellular animals possessing a nervous system, the cnidarian Renilla koellikeri, aminergic-like receptors were previously characterized pharmacologically and found to engender control of the animal's bioluminescent and peristaltic reactions. Using degenerate oligonucleotides in a RT-PCR strategy, we obtained a full-length cDNA encoding a polypeptide with typical G protein-coupled receptor (GPCR) characteristics and which displayed a significant degree of sequence similarity (up to 45%) to biogenic amine receptors, particularly dopamine and adrenergic receptors. The new receptor, named Ren1, did not resemble any one specific type of amine GPCR and thus could not be identified on the basis of sequence. Ren1 was expressed transiently and stably in cultured mammalian cells, as demonstrated by immunocytochemistry and western blotting. Functional analysis of transfected HEK293, LTK- and COS-7 cells, based on both cAMP and Ca2+ signalling assays, revealed that Ren1 was not activated by any of the known biogenic amines tested and several related metabolites. The results indicated, however, that cells stably expressing Ren1 contained, on average, an 11-fold higher level of cAMP than the controls, in the absence of agonist stimulation. The high basal cAMP levels were shown to be specific for Ren1 and to vary proportionally with the level of Ren1 expressed in the transfected cells. Taken together, the data suggested that Ren1 was expressed as a constitutively active receptor. Its identification provides a basis for examination of the early evolutionary emergence of GPCRs and their functional properties.

Sulfated cyclodextrins for the chiral separations of catecholamines and related compounds in the reversed electrophoretic polarity mode

The utility of negatively charged sulfated cyclodextrins (SCD) as chiral additives (CA) in capillary electrophoresis (CE) was studied in the chiral resolution of several compounds of pharmaceutical interest, including catecholamines such as norepinephrine, epinephrine, DOPA and their precursors, phenylalanine, and tyrosine. Experiments were conducted using 10 mM sodium phosphate monobasic solution and 2% SCD adjusted to pH 3.2 with phosphoric acid. Chiral recognition mechanisms were explored using structurally related analytes including basic, acidic, and neutral compounds as well as 3,5-dinitrobenzoyl phenylglycine, phenylalanine, and homophenylalanine. The advantage of the reversed electrophoretic polarity mode for the enantioresolution of these compounds is also discussed.

Biogenic amines in coelenterates

1. This mini review highlights the most important findings during three decades of research on biogenic amines in coelenterates. 2. Histochemical, analytic chemical and physiological evidences clearly indicate that dopamine is used as an intercellular messenger in hydrozoans. 3. The colonian anthozoan Renilla, has beta-adrenergic mechanisms in monitoring bioluminescence and serotoninergic mechanisms in rhythmic contractions.

Determination of gamma-glutamyl conjugates of monoamines by means of high-performance liquid chromatography with electrochemical detection and application to gastropod tissues

Catabolism of aminergic neurotransmitters in gastropods appears to be primarily by means of gamma-glutamyl conjugation rather than by oxidative deamination as is typical of vertebrates. High-performance liquid chromatography with electrochemical detection was used to develop a method for the routine measurement of gamma-glutamyl conjugates of dopamine and 5-hydroxytryptamine in gastropod tissues.

3,4-Dihydroxyphenylethylamine, L-3,4-dihydroxyphenylalanine and 3,4,5-trihydroxyphenylalanine: oxidation and binding to membranes. A comparative study of a neurotransmitter, a precursor and a neurotransmitter candidate in primitive nervous systems

At neutral (7.0) and slightly basic (8.2) pH, L-3,4-dihydroxyphenylalanine (L-DOPA), 3,4,5-trihydroxyphenylalanine (5-OH-DOPA) and 3,4-dihydroxyphenylethylamine (dopamine) undergo autoxidation. The binding of radiolabeled oxidation products of L-DOPA, 5-OH-DOPA and dopamine to membrane proteins was compared by a filtration procedure. Membranes from tentacles of the sea anemone Metridium senile bind significantly more 5-OH-DOPA than L-DOPA and dopamine. Membranes from rat brain and brains from the three-spined stickleback Gasterosteus aculeatus, bind significantly more dopamine than L-DOPA and 5-OH-DOPA. Membranes from Metridium contain an o-diphenol O2: oxidoreductase (tyrosinase). In the absence of inhibitors, enzymatic oxidation causes a fiftyfold increase in binding of L-DOPA and a more than tenfold increase in binding of dopamine, whereas the binding of 5-OH-DOPA only is increased by 10%. It is concluded than 5-OH-DOPA more easily undergo autoxidation than L-DOPA and dopamine, but its quinone form is probably less reactive with membrane proteins. The suitability of tyrosinase-mediated biosynthesis of L-DOPA and 5-OH-DOPA versus tyrosine hydroxylase-mediated biosynthesis of L-DOPA and dopamine in primitive nervous systems and in the vertebrate CNS is discussed on the basis of the cytotoxic potential through irreversible binding to membrane proteins of oxidation products of the catechol compounds formed.