PINEAL PHOTORECEPTORS RHYTHMICALLY SECRETE MELATONIN

Individual pineal cells secrete melatonin with a circadian period, red ucing a vertebrate circadian system to the level of a single cell Bra in Res., 627 (1993) 141-146. In the present study, dissociated pineal cells were identified as melatonin-secreting by a reverse hemolytic p laque assay (RHPA) and all melatonin-secreting cells were immune-posit ive when analyzed for the photoreceptor protein S-antigen. The results are the first direct evidence that isolated photoreceptor cells secre te melatonin and taken together with our previous findings indicate th at single pineal cells contain: (1) a circadian oscillator; (2) a phot oreceptive capacity; and (3) the ability to secrete melatonin rhythmic ally.