Action of endothelins and related substances on the chromatophores of poikilothermal vertebrates

点击翻译按钮获取中文摘要

Working on the medaka, Oryzias latipes, the changes in the responsiveness of melanophores to electrical nervous stimulation after prolonged background adaptation were investigated. It was found that the excitability of the chromatic nerves and the density of innervation were largely affected during the background adaptation (Sugimoto et al., 1994). Then, the pharmacological profiles of the muscarinic cholinoceptors that mediate aggregation of pigment in the melanophores were stidied on two species of catfish. It was indicated that thses receptors resembled those of mammalian muscarinic cholinpceptors of the M_3 type (Hayashi and Fuji, 1994). Morphological observations about the skin of the common surgeonfish, paracanthurus hepatus, showed that the blue coloration was due to the presence of iridophores resembling those of blue damselfish, but the iroidophores existed in double starta (Goda et al., 1994). Novel blue chromatophores were found in two species of callionymid fish. We named them the "cyanophores", and the blue organelles contained the "cyanosomes" (Goda and Fujii, 1995). Pharmacological studies on the endothelin receptors that mediate aggregation of pigment in fish melanophores were intensely studied. The conclusion was that they resembled those of the mammalian ET_B type (Hayashi and Fujii, in press). Including those of endothelins and of related substances, the effects of vaious factors influencing motile activities of fish chromatophores were widely discussed in a review article by us (Fujii and Oshima, 1994).