. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 366 M- NAGAI ET 50mM 3«10~9M 3*10~9M I 1 2* 2+ ' ' -5 Ca .Mg r(ree saline (+1 ) Arh[5xlO M, FIGURE 6. Typical recording of the response of Japanese common catfish (Parasilurus asotus) mela- nophores to MCH, showing that the pigment-aggregating effect of the peptide was still remarkable in Ca2+- free saline, in which the release of peripheral stores of neurotransmitter (ACh) was inhibited. 50 mM K+ Ringer (K+) was used for neural stimulation. Finally, 5 X 10~5 Macetylcholine(ACh)was applied to induce the full aggr
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 366 M- NAGAI ET 50mM 3«10~9M 3*10~9M I 1 2* 2+ ' ' -5 Ca .Mg r(ree saline (+1 ) Arh[5xlO M, FIGURE 6. Typical recording of the response of Japanese common catfish (Parasilurus asotus) mela- nophores to MCH, showing that the pigment-aggregating effect of the peptide was still remarkable in Ca2+- free saline, in which the release of peripheral stores of neurotransmitter (ACh) was inhibited. 50 mM K+ Ringer (K+) was used for neural stimulation. Finally, 5 X 10~5 Macetylcholine(ACh)was applied to induce the full aggregation of melanosomes. The relationship between the strength of MCH and the magnitude of the target cell response in the glass catfish and the common siluroid was revealed to be dose- dependent, as shown in Figure 1. In both species, the threshold concentration was estimated to be not more than 10"'° M, and a response larger than 80% of the maxi- mal one was induceable at a concentration of 10~9 M. Effects of MCH on melanophores possessing both alpha-adrenoceptors and chohnoceptors Melanophores of the mailed catfish of the genus Corydoras (Callichthyidae, Silur- iformes) possess melanosome-aggregating cholinoceptors of the muscarinic type, not- withstanding the fact that they are also under the control of adrenergic fibers (Kasu- kawa and Fujii, 1985; Kasukawa et al, 1986; cf. also Table I). Employing a represen- tative species from this genus, , the peppered catfish (C. paleatus), we found that MCH had the same potent action to aggregate melanophore inclusions as it did in other teleosteans. Neither adrenolytic nor muscarinic cholinolytic agents interfered with the MCH effect. Furthermore, Ca2+-withdrawal did not affect the responsiveness to the hormone. DISCUSSION Using a number of teleost species from a variety of families and orders, we have demonstrated in the present study that MCH is very effective in bringing about a notable pigment aggregation not only in a
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
