THE ROLE OF AMBIENT LIGHTING IN CIRCADIAN DISK SHEDDING IN THE ROD OUTER SEGMENT OF THE RAT RETINA

  • 1 January 1980
    • journal article
    • research article
    • Vol. 19  (11) , 1257-1267
Abstract
Rats raised from birth on a 0700 h:1900 h light cycle exhibited a circadian burst of photoreceptor shedding 1 1/2 h after the scheduled onset of light. This rhythmic event persisted even after the animals were placed in total darkness for up to 2 wk. When animals were placed in constant light (LL) for more than 24 h, the shedding peak was abolished. A period of darkness of at least 2 h, ending at the normal time for light onset, was necessary for the production of a shedding burst. When animals were placed in altered lighting cycles, the shedding rhythm shifted accordingly, although the speed of this shift was greatest with large advances in the light cycle and slowest with small delays in the light cycle. Animals exposed to LL and then returned to the dark exhibited the original shedding rhythm. This phenomenon was not affected when the optic nerves were severed. A shedding peak was induced at a noncircadian time by exposing the animals to more than 20 h of LL followed by 2 h of darkness and 1 1/2 h of light; the magnitude of the shedding was related to the circadian time.