AbstractThe possibility of adrenergic innervation to melanophores in scales ofOryzias latipeswas investigated using3H‐norepinephrine (3H‐NE) by light microscopic autoradiography. When isolated scales were incubated in3H‐NE, there was observed plexus of varicose fibers labeled with3H‐NE which intimately enclosed the stellate processes and cell bodies of melanophores. These labeled fibers could not be detected in cocaine‐treated or denervated scales. Potassium ions caused a considerable reduction in the labeling of varicose fibers, which was accompanied with aggregation of melanosomes within melanophores. These findings suggest that the labeled fibers observed are compatible with adrenergic nerve fibers that control the melanosome movements within mel