[Role of neuronal and neuropile serotonin in the visual analyzer]

The serotonin content was estimated in bulk-separated neuronal and neuropil fractions of visual and motor brain cortex in normal, dark-reared and light-exposured rats. In normal rats, the serotonin content in neuropil in visual and motor cortex was equal to 182.66 +/- 21.19 and 164.10 +/- 27.70 ng/mg protein, respectively, and exceeded its content in neuronal fractions 2.7-fold (for visual cortex) and 2.2-fold (for motor cortex). Under dark-rearing the serotonin content in neuropil of visual and motor cortex decreased by 46.7 and 51.6%, respectively, as compared with normal. Light exposure of dark-reared rats for 3 hours produced a sharp increase in the serotonin content only in neuropil of visual cortex (2.7-fold higher in comparison with dark-reared rats). There were no significant changes in the serotonin content in neurons of both cortical regions under the experimental conditions used as compared with normal. The results are discussed from the point of view of functional heterogeneity of serotonin metabolism in neurons and neuropil.