Adrenergic nerves and the alpha 2-adrenoceptor system regulating melanosome aggregation within fish melanophores.
Nervous control of melanosome aggregation of melanophores of Labrus ossifagus was studied by electrical field stimulation of isolated scales. Field stimulation elicited a rapid melanosome aggregation which was reversible upon interruption of the stimuli. The response was blocked by guanethidine indicating that adrenergic nerves were stimulated. The melanophore receptors which mediate the nerve-controlled pigment aggregation were characterized to be of the alpha 2-adrenoceptor subtype, since they were inhibited by yohimbine but not by prazosin. Stimulation of the alpha 2-adrenoceptors by noradrenaline was associated with a significant reduction of the cyclic AMP content of the melanophores. It is suggested that adrenergic nerves control melanosome aggregation via alpha 2-adrenoceptors and that these receptors are coupled to the adenylate cyclase-cyclic AMP system of the melanophores.
D000320:Adrenergic Fibers / Q000502:physiology*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002449:Cell Aggregation / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D004558:Electric Stimulation; D005399:Fishes / Q000502:physiology*; D008544:Melanocytes / Q000502:physiology*; D008547:Melanophores / Q000502:physiology*; D011941:Receptors, Adrenergic / Q000502:physiology*
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011941:Receptors, Adrenergic; D000242:Cyclic AMP