Horizontal cell signal is smaller with texture-like nonuniform patterns than with uniform fields of the same space-average illuminance

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.

Measurement of DC and AC spectral sensitivities of retinal horizontal cells by "voltage clamp by light"

The method of "voltage clamp by light" was applied to measure spectral sensitivities of second-order visual neurons, namely L- and R/G-type horizontal cells in the carp retina. The present equipment employs (i) a ceramic photomodulator to facilitate a fast servomechanical control of retinal illuminance, (ii) an electronic circuit to compensate for the synaptic transmission delay, and (iii) a manual selection switch for the system to operate on negative feedback for either depolarizing or hyperpolarizing responses to light. These features allowed us to determine quickly and simultaneously both DC and AC spectral sensitivities, although the AC case was examined only at 1 Hz in this report. In L-type cells, the AC spectral sensitivity was similar in shape to the DC result. These sensitivity curves differed from microphotospectrometric absorption of red-sensitive cones: in L-type cells at both ends of the visible spectrum and in R/G units with deep-red light.