An increase in extracellular Ca(2+) concentration induces pigment aggregation in teleostean melanophores.
An increase in the concentration of Ca(2+) ions in the external medium ([Ca(2+)](o)) induced pigment aggregation in melanophores of three species of freshwater teleosts examined. Denervated melanophores were refractory to elevations of [Ca(2+)](o). The pigment-aggregating action was inhibited by the sympathetic blocking agents, phentolamine, prazosin and yohimbine. Bretylium, an agent known to block the release of the neurotransmitter, interfered with the response effectively. Ca(2+) blockers, such as Mn(2+), verapamil and gallopamil, also inhibited the response, possibly by inhibiting Ca(2+) entry into the presynaptic elements of melanosome-aggregating fibers. The conclusion is that the increase in [Ca(2+)](o) may induce membrane depolarization of presynaptic nervous elements around the melanophores, which open the voltage-dependent Ca(2+) channels there. The liberation of adrenergic neurotransmitter follows, which induces the aggregation of pigment in melanophores.
Department of Biomolecular Science, Faculty of Science, Toho University, Funabashi, Chiba, Japan. ts-yamada@fujirebio.co.jp
Takashi
T
Yamada
Ryozo
R
Fujii
D000109:Acetylcholine / Q000494:pharmacology; D018663:Adrenergic Agents / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005399:Fishes / Q000378:metabolism*; D008547:Melanophores / Q000187:drug effects* / Q000378:metabolism*; D010860:Pigments, Biological / Q000378:metabolism*; D013565:Sympatholytics / Q000494:pharmacology
D018663:Adrenergic Agents; D002121:Calcium Channel Blockers; D010860:Pigments, Biological; D013565:Sympatholytics; D000109:Acetylcholine; D002118:Calcium