The influence of different light intensities on pineal melatonin content in the retinal degenerate C3H mouse and the normal CBA mouse.

The sensitivity of light-induced suppression of pineal melatonin content was compared between C3H mice with hereditary retinal degeneration and CBA mice with normal retinas. At 2 h before lights on of light-dark (LD) cycles, when pineal melatonin content is the highest in both strains, groups of mice were exposed to different intensities of white fluorescent light (100, 0.14, 0.017 lux in both strains and 0.0021 and 0.00026 lux in CBA mice). For each intensity, pineals were collected just before and 5, 15 and 30 min after exposure to light. In C3H mice, the threshold of light intensity to suppress pineal melatonin content was between 0.14 and 0.017 lux, whereas that in CBA mice was between 0.0021 and 0.00026 lux. These results suggest that both rods and cones mediate photic information to the pineal gland in mice.