SPECIAL LIGHT ADAPTIVE PROPERTIES OF INDOLEAMINE SECRETING PINEAL PHOTORECEPTORS

Pineal photoreceptors in the trout do not adapt during sustained illumination, contrary to the general rule that receptor cells, including retinal photoreceptors, lose sensitivity on prolonged stimulation. This unique feature seems necessary to maintain the voltage dependent metabolism and secretion of indolamine by pineal photoreceptors locked to the level of daily illumination.