. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 364 M. NAGAI ET AL. * 70h A g. FIGURE 2. A set of recordings of the response of melanophores of the topmouth gudgeon, Psendoras- bora parva, indicating that MCH had no pigment-dispersing effect. The recordings were obtained on different scales but from the same fish. The magnitude of response is expressed as the percentage of the maximal level of pigment aggregation. In each recording, the scale was first treated with 10~6 M melatonin (MT) for 4 min. Then the perfusing medium was changed to physiological saline (A), 10~8 M M
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 364 M. NAGAI ET AL. * 70h A g. FIGURE 2. A set of recordings of the response of melanophores of the topmouth gudgeon, Psendoras- bora parva, indicating that MCH had no pigment-dispersing effect. The recordings were obtained on different scales but from the same fish. The magnitude of response is expressed as the percentage of the maximal level of pigment aggregation. In each recording, the scale was first treated with 10~6 M melatonin (MT) for 4 min. Then the perfusing medium was changed to physiological saline (A), 10~8 M MCH (B), ortolO-7MMSH(C). pie of this differential responsiveness to melatonin is exhibited in the melanophores of the topmouth gudgeon (Fig. 3B). On the other hand, the response to MCH pro- ceeded quite simultaneously among the cells (Fig. 3C). An alpha-adrenolytic agent, phentolamine, had no influence on the melanin-ag- gregating action of the peptide. As an example of the records, the response of the topmouth gudgeon is exhibited in Figure 4. The melanin-aggregating action of K+, however, was easily inhibited by phentolamine. This ion has been known to act on chromatic neural elements around the pigment cells to release neurotransmitter (Fujii, 1959). It was concluded, therefore, that MCH acts directly on the target cells and not through activities of the neural elements. Although not shown in the figure, it was further shown that a beta adrenergic blocker, propranolol, had no effect on the action of MCH. These results further indicate that MCH acts independently of alpha and beta Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Rattray, 1870-1947; M
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