A possible functional relationship between the subcommissural organ and the pineal complex and lateral eyes in Rana esculenta and Rana temporaria.

In previous publications (Diederen, 1972, 1973) evidence was presented that light and darkness hardly influence the secretory activity of the subcommissural organ (SCO) in intact frogs, i.e. frogs in which all photo-receptive organs are present. In the present study the influence of long daily photoperiods and of continuous darkness on the SCO of frogs in which the frontal organ, the pineal organ and the eyes were eliminated separately or in combination was studied. The parameters used to measure the secretory activity of the SCO were the amount of aldehyde-fuchsin(AF)-positive material in the SCO cells, the incorporation of 35S-cysteine by the SCO cells and the growth rate of Reissner's fibre (RF). Only in frogs in which the eyes as well as the entire pineal complex were eliminated was an unequivocal influence of light and darkness on the secretory activity of the SCO demonstrable: in blinded frogs without a pineal complex, the growth rate of RF is clearly enhanced in animals exposed to light. If the eyes or the pineal complex or the pineal organ alone have not been eliminated, then the stimulatory influence of light on the growth rate of RF can no longer be detected. This indicates that light causes the pineal complex and the eyes to exert an inhibitory influence on the secretory activity of the SCO. The hypothesis is put forward that in intact frogs influences of light on the secretory activity of the SCO, at least so far as the production of RF is concerned, are prevented by the photo-receptive organs. In this way a functional relationship between the SCO on the one hand and the pineal complex and eyes on the other hand may be expressed. A mechanism by which the influences of light on the SCO may be prevented by the pineal complex and the eyes is suggested.