Benzodiazepine receptors in the visual structures of monocularly deprived rats. Effect of light and dark adaptation

Abstract

In 25-day-old rats with one eyelid sutured at the age of 10 days, the binding of [ 3H]flunitrazepam in the visual structures (retina, lateral geniculate nucleus, superior colliculus, visual cortex) and frontal cortex was determined. Monocular visual deprivation (MD) resulted in a significant decrease of the [ 3H]flunitrazepam binding in the retina of the open eye to about 76% of the control value. No changes in [ 3H]flunitrazepam binding were detectable under these conditions in the central visual structures examined and the non-visual cortical region. Scatchard analysis indicated that the changes found in the retina of the open eye of MD rats are due to a decreased binding affinity only, the maximum receptor number being unaffected. Eight hours after re-opening the sutured eyelid of 25-day-old MD rats, benzodiazepine binding in the open eye was increased to the control level, whereas the binding in the retina of the re-opened eye remained unchanged in comparison to control animals. Dark adaptation of 25-day-old control rats resulted in an increased [ 3H]flunitrazepam binding in the retina by 28% compared to that detectable in the retina of light-adapted animals. In contrast, dark-adaptation of MD rats did not affect [ 3H]flunitrazepam binding in the retina of both eyes in comparison to that found in the corresponding retina of light-adapted MD animals. The data obtained suggest a physiological coupling between both retinas, possibly mediated through centres inside of the central nervous system.