Serotoninergic receptors in the visual system of light-deprived rats

The level of binding of [(3)H]serotonin (5-hydroxytryptamine) to serotonin type 1 receptors (S1) in the visual centres and frontal cortex of control, dark reared and monocularly deprived (one eyelid sutured on postnatal day 10) 3-month-old rats were determined and compared to that assayed in 25-day-old rats. The two forms of light deprivation affect [(3)H]serotonin binding in the central visual structures in a different way. Monocular deprivation until the age of 3 months resulted in decreased serotonin binding levels in the retina of both eyes compared to the control group raised under a 12 h light-dark cycle. Additionally, serotonin binding in the lateral geniculate nucleus contralateral to the closed eye is decreased. Rearing rats in complete darkness from birth to the age of 3 months leads to an increase of serotonin binding in the visual cortex and superior colliculus. Regarding the normal distribution of serotonin type 1 binding sites in the visual system of 3-month-old rats, highest serotonin binding is found in the lateral geniculate nucleus followed by the retina, superior colliculus and visual cortex. The differential effect of monocular or total light deprivation upon serotonin type 1 receptors in the different visual nuclei might reflect differences in the morpho-functional organization of the serotoninergic system along the visual pathway and its involvement in visual information processing.