Single-unit electrophysiological experiments were conducted on albino rats housed in either cyclic light or constant light for as long as 24 weeks. Histological examination of the retinas of the constant light-exposed rats confirmed that there was a massive degeneration of the photoreceptor cells. Despite this degeneration, visually responsive cells were found in the lateral geniculate nucleus (LGN) and the visual cortex (VC) at all exposure times. With increasing exposure times, we found that cells in the LGN and VC had longer response latencies and less vigorous responses and that it was necessary to illuminate larger areas of the visual field in order to produce responses. Studies of LGN cells in control and experimental rats showed that the spectral sensitivities of those cells were similar in shape and peak sensitivity to the spectral absorption properties of rhodopsin. In view of this fact, it seems most likely that rhodopsin is the primary light-transducing molecule in the retina of rats exposed to long-term constant light. The spectral sensitivity curves of some cells in control animals and light-exposed animals had minor peaks at 600 nm, which may have been due to some additional visual pigment molecule.
ASJC Scopus subject areas
- Developmental Neuroscience