Summary

1. 1. A fast transient peak of light, followed by a slow luminescence, was produced by isolated photophores of Porichthys notatus when exposed to 1 mM-epinephrine, norepinephrine or phenylephrine, an α-adrenergic agonist. Only a slow luminescence was induced by 1 mM-isoproterenol, the β-adrenergic agonist.

2. 2. After removal of the reflector and surrounding tissues, the isolated photogenic cells, i.e. the photocytes, responded to norepinephrine and phenylephrine by producing a fast transient peak of light, and to isoproterenol by a slow luminescence. Epinephrine evoked both types of luminescence. The emission latency time, the amplitude and the total duration of the light responses were significantly less than those of the photophore.

3. 3. The results suggest that both epinephrine and norepinephrine combine with sympathetic α or β receptors upon the photocytes to trigger light production.