[Serotonin concentration and tryptophan-5-hydroxylase activity in the visual system of the rat brain during ontogeny]

The dynamics of 5-hydroxytryptamine (5-HT) content and tryptophan-5-hydroxylase activity in the visual analyzer formations (external geniculate body, bigeminal bodies, visual cortex) and the locomotory cortex was studied in the rat brain during postnatal ontogenesis. Both the parameters were determined by means of spectrofluorometry. Each formation and locomotory cortex were shown to differ between each other by 5-HT content and tryptophan-5-hydroxylase activity. The level of 5-HT in various brain formations of 3 days old rats was low and increased during postnatal ontogenesis. The adult level of 5-HT was attained at different times: in the external geniculate body from the 1st and in the visual cortex from the 6th week after birth. Beginning from the first days of life tryptophan-5-hydroxylase was able to provide for 5-HT synthesis at the adult level. The correlation of the enzyme activity and 5-HT content during postnatal ontogenesis was noted only in the external geniculate body and visual cortex. Possible mechanisms of fluctuations in 5-HT content and tryptophan-5-hydroxylase activity in the rat brain formations under study during postnatal ontogenesis are discussed.