A Comparison of Transmitter and Synephrine on Luminescence Induction in the Firefly Larva

Smalley (1965) demonstrated that the adult firefly lantern can be classified as adrenergic with respect to a number of criteria established for vertebrate sympathetic junctions. The lantern luminesces in response to adrenaline and its analogues. Amphetamine acts indirectly to induce luminescence and fails in denervated lanterns. Reserpinized lanterns respond to adrenaline, but no longer to neural stimulation. Carlson (1968 a) demonstrated that the lanterns of the larval firefly respond in similar fashion to the adult lantern. In this system the lanterns were immersed in oxygenated saline and luminiscence could be induced by introduction of adrenaline and its analogues. Synephrine (p-hydroxy-a-[(methylamino) methyljbenzyl alcohol) was found to have the highest potency, initiating luminescence at a concentration of io~" M (Carlson, 19686) and it acted in identical fashion to adrenaline, which was 45 times less potent. Transmitter could be released to act either by neural stimulation or by immersion of the lantern in K saline (Carlson, 1968 a). It now becomes possible to compare the actions of synephrine and transmitter in luminescence induction. This promises to allow one to determine whether these substances differ qualitatively in their pharmacological actions. This is a report of a comparative study of the effects of transmitter and synephrine. It should be emphasized at the outset that these substances are applied in somewhat different fashion and this in itself may have produced qualitative differences in their luminescence inducing actions.