Intracellular responses from UV-sensitive cells in the photosensory pineal organ.

A new type of cell having high sensitivity in the ultraviolet (UV) range was found in the pineal organ of the river lamprey. Lampetra japonica, by intracellular recordings. This UV-sensitive cell responded to light with graded hyperpolarizations and had the maximum sensitivity at 380 nm. The response of the cell was much slower than that of the usual pineal photoreceptor with the peak spectral sensitivity at 525 nm. Intracellular injection of Lucifer yellow revealed that the cell consists of 3 parts, corresponding to an outer segment, an inner segment and a terminal of photoreceptor cell. The apical part of the cell protruded into the lumen and the inner segment situated in the layer of photoreceptor cells. It was concluded that this UV-sensitive cell was a UV-specific receptor cell.