Responses of the melanophores of the medaka, Oryzias latipes, to adrenergic drugs: evidence for involvement of alpha 2 adrenergic receptors mediating melanin aggregation.
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.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003532:Cyprinodontiformes / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D046911:Macromolecular Substances; D008543:Melanins / Q000378:metabolism*; D008547:Melanophores / Q000187:drug effects / Q000502:physiology*; D009990:Oryzias / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D046911:Macromolecular Substances; D008543:Melanins; D011942:Receptors, Adrenergic, alpha