Responses of the melanophores of the medaka, Oryzias latipes, to adrenergic drugs: evidence for involvement of alpha 2 adrenergic receptors mediating melanin aggregation |
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Authors: | F Morishita |
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Institution: | Zoological Institute, Faculty of Science, Hiroshima University, Japan. |
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Abstract: | 1. Melanin-aggregation response of the medaka melanophores to a series of adrenergic drugs were examined. 2. Concentration-response curves for the drugs indicated that the melanin-aggregating effects of alpha 2 adrenergic agonists, naphazoline, tramazoline and clonidine, were more than 100-fold greater than that of alpha 1 agonists, phenylpropanolamine, phenylephrine, oxymetazoline and methoxamine. 3. The inhibitory effect of alpha 2 antagonist, yohimbine, on the cell responses to the agonists were also about 100-fold greater than that of alpha 1 antagonists, corynanthine and prazosin. 4. These results indicate that adrenergic receptors which mediate melanin-aggregation response of the cells are alpha 2 in nature. |
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