Abstract
Pineal organs of poikilotherm animals have photoreceptor cells with cone type structures of disk membranes of the outer segment. In the lamprey, Lampetra japonica, photoreceptors responded to light at 6×10-4 lux as a threshold with hyperpolarization, which modulated the spike discharge of the ganglion cells. Electrophysiological data and high performance liquid chromatography analysis of visual pigments of the pineal suggested the presence of several types of photoreceptor cells. Actually, two different immunoreactivities were observed in photoreceptors by using antibodies against rod specific protein and cone specific protein. Light information of the environment perceived by the pineal organ is transmitted to the central nervous system and contributes to the control of the locomotor activity rhythm of the lamprey.
