Dark-rearing affects the development of benzodiazepine receptors in the central visual structures of rat brain

The postnatal development of [3H]flunitrazepam binding to benzodiazepine receptors has been studied in the retina, lateral geniculate nucleus, superior colliculus, frontal cortex and visual cortex of the rat. In the frontal and visual cortices, binding reached the highest level at postnatal day 25 and then decreased slightly until adulthood. In the superior colliculus, the adult value of [3H]flunitrazepam binding is already reached at postnatal day 25, whereas in the retina the highest binding was found at postnatal day 50. The ontogeny of benzodiazepine binding sites in the visual regions does not essentially differ from that in other brain regions, suggesting that the appearance of [3H]flunitrazepam binding sites in the visual system is not correlated with the development of retinal function and the functional maturation of the visual system with regard to processing of light stimuli. Raising rats in complete darkness from birth until the age of 25 days resulted in significantly decreased binding levels in the lateral geniculate nucleus and in the superior colliculus by 29% and 17%, respectively, as compared to controls. [3H]Flunitrazepam binding in the other regions studied was not affected by dark-rearing. Presumably, the complete lack of visual experience interferes with the functional development of GABAergic mechanisms involved in the gating function of the subcortical visual centres for visual information transfer.