Dopamine and serotonin modulate the onset of metamorphosis in the ascidian Phallusia mammillata.
Neurotransmitters play an important role in larval metamorphosis in different groups of marine invertebrates. In this work, the role of dopamine and serotonin during metamorphosis of the ascidian Phallusia mammillata larvae was examined. By immunofluorescence experiments, dopamine was localized in some neurons of the central nervous system and in the adhesive papillae of the larvae. Dopamine and serotonin signaling was inhibited by means of antagonists of these neurotransmitters receptors (R(+)-SCH-23390, a D(1) antagonist; clozapine, a D(4) antagonist; WAY-100635, a 5-HT(1A) antagonist) and by sequestering the neurotransmitters with specific antibodies. Moreover, dopamine synthesis was inhibited by exposing 2-cell embryos to alpha-methyl-l-tyrosine. Dopamine depletion, obtained by these different approaches, caused early metamorphosis, while serotonin depletion delayed the onset of metamorphosis. The opposite effects were obtained using agonists of the neurotransmitters: lisuride, a D(2) agonist, inhibited metamorphosis, while DOI hydrochloride and 8-OH-DPAT HBr, two serotonin agonists, promoted it. So, it is possible to suppose that dopamine signaling delayed metamorphosis while serotonin signaling triggers it. We propose a mechanism by which these neurotransmitters may modulate the timing of metamorphosis in larvae.
Zega
Giuliana
G
Dipartimento di Biologia, Università di Milano, Via Celoria 26, I-20133, Milano, Italy. giuliana.zega@unimi.it
Pennati
Roberta
R
Groppelli
Silvia
S
Sotgia
Cristina
C
De Bernardi
Fiorenza
F
D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D003024:Clozapine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006652:Histological Techniques; D007150:Immunohistochemistry; D007814:Larva / Q000187:drug effects / Q000502:physiology; D008090:Lisuride / Q000494:pharmacology; D008675:Metamorphosis, Biological / Q000187:drug effects / Q000502:physiology*; D008781:Methyltyrosines / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D014561:Urochordata / Q000187:drug effects / Q000254:growth & development*
D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D008781:Methyltyrosines; D010879:Piperazines; D011725:Pyridines; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D008090:Lisuride; D003024:Clozapine; D004298:Dopamine