Rats were exposed to 490- to 580-nm light in green Plexiglas
chambers
1 (no. 2092; Dayton Plastics, Dayton, OH)
beginning at various times of the day or night. The animals were
unanesthetized and unrestrained during light exposure. Light intensity
during exposure was 1200 to 1400 lux, approximately 200μ
W/cm
2 corneal irradiance (light meter 1 L
1400A; International Light, Newburyport, MA). Rats from the dim cyclic
light environment were normally treated with intense light for 8 hours.
Because of their greater light damage susceptibility,
7 dark-reared rats were exposed to light for 3 hours. These exposure
times resulted in approximately 50% visual cell loss for rats treated
with light beginning at 0100 and were selected as the criterion for
relative light damage susceptibility in this study (cf.
Figs. 1 and 4 )
and as a means to demonstrate the efficacy of antioxidant treatments in
previous work.
8 9 10 11 In some experiments longer or shorter
light treatments were used. Some rats were given the synthetic
antioxidant dimethylthiourea (DMTU) at a dose of 500 mg/kg IP, one or
two times, before or during light treatment.
7 11 After
treatment the rats were either killed immediately in a
CO
2-saturated chamber or were maintained in
darkness for 2 additional weeks before use.