Noradrenaline- and Melatonin-Mediated Regulation of Pigment Aggregation in Fish Melanophores


  • Present address: Helén Nilsson Sköld, Kristineberg Marine Research Station, Swedish Royal Academy of Science, Fiskebäckskil, Sweden.

    Present address: Gabriela Quiroga, Department of Natural Sciences, Södertörn University College, Huddinge, Sweden.

* Address reprint requests to Sara Aspengren, Department of Zoology, Zoophysiology, Göteborg University, Box 463, 405 30 Göteborg, Sweden. E-mail:


The effects of melatonin and noradrenaline (NA) on bi-directional melanosome transport were analysed in primary cultures of melanophores from the Atlantic cod. Both agents mediated rapid melanosome aggregation, and by using receptor antagonists, melatonin was found to bind to a melatonin receptor whereas NA binds to an α2-adrenoceptor. It has previously been stated that melatonin-mediated melanosome aggregation in Xenopus is coupled with tyrosine phosphorylation of a so far unidentified high molecular weight protein and we show that although acting through different receptors and through somewhat different downstream signalling events, tyrosine phosphorylation is of the utmost importance for melanosome aggregation mediated by both NA and melatonin in cod melanophores. Together with cyclic adenosine 3-phosphate-fluctuations, tyrosine phosphorylation functions as a switch signal for melanosome aggregation and dispersion in these cells.