Characterization of the day-night variation of retinal melatonin content in the chick.

摘要: By monitoring two time points (one at mid-light and the other mid-dark), day-night variation of melatonin content in retina 19-day-old chicks was characterized. Melatonin detected plus attached pigment epithelium by a specific radioimmunoassay, its identity verified high performance liquid chromatography with electrochemical detection. posterior pole eye showed fivefold variation, levels during dark period diurnal lighting. Light exposure lowered normally nighttime value; maintenance darkness normal light did not alter low values typical mid-light. Pineal responded similarly to above lighting manipulations. Neither pinealectomy nor optic nerve transection had an effect on retina-pigment or light-dark rhythm. We next examined relative contributions retinal pineal blood levels. Pinealectomy reduced mid-dark plasma value 80%. The addition bilateral enucleation another 9% control values. first evident embryo 2 days prior hatching persisted through adulthood. It concluded that chick from latter stages embryonic development is capable rhythmically synthesizing melatonin; displays photically controlled circadian rhythm phase with, but independent of, gland; regulated afferent fibers. gland major source intact chick, most small contribution retina.