EFFECTS OF GENOTYPE-GLUCOCORTICOID INTERA CTION OF THE TYROSINE-HYDROXYLASE ACTIVITY IN THE BRAIN OF RAT FETUSES

The activity of the rate-limiting enzyme of catacholamine synthesis -- the tyrosine hydroxylase (TH) increased in the brain of 20-day-old fe tuses of the Wistar strain and agressive gray rats, 6 hours after cort icosterone injection to their mothers. However, this treatment had no effect on the TH activity of 20-day-old fetuses of tame gray rats. Cor ticosterone injection to the females of these strains on the 16th and 18th days of pregnancy caused inhibition of the fetal development with in 3 days, assessed by measuring the fetal body weight, and alteration s in the TH activity of the fetal brain. Inhibition of the development of Wistar fetuses was accompanied by decrease in the TH activity at 2 4-day age. The body weight of the 21-old fetuses of agressive rats did not change and their TH activity increased after hormonal treatment. Corticosterone inhibited general development of 21-day-old fetuses of tame gray rats, and the TH activity in their brains was not elevated. Thus, glucocorticoids stimulate the development of the catecholaminegi c system by increasing the TH activity and inhibit it via catabolic ac tion. Each of these effects displays hereditary variability. Simultane ous realization of these opposite actions of the hormone can create th e basis for the effect of interaction between the genotype and the glu cocorticoid-mediated environmental influences on the development of th e neurotransmitter system of the brain.