Effect of postnatal exposure to GABA agonist muscimol on age-related changes in hypothalamic noradrenaline concentration in rats.

Concentrations of cortical and hypothalamic monoamines and their metabolites after postnatal administration of the GABAA agonist muscimol or ethanol were studied in 37- and 120-day-old rats to clarify the role of GABAergic mechanisms in the development of central monoaminergic neurons. In control rats the hypothalamic noradrenaline (NA) concentration tended to be higher in 120-day-old rats when compared to 37-day-old controls, whereas in muscimol-treated rats the hypothalamic NA concentration was decreased as a function of age. Concentrations of dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were increased in the hypothalamus as a function of age regardless of postnatal treatment. In the cerebral cortex there was an age-dependent increase in the concentrations of NA, serotonin (5-HT), and 5-hydroxyindoleacetic acid (5-HIAA), as well as a decrease in the concentration of homovanillic acid (HVA) and 5-HIAA/5-HT and HVA/DA ratios in all rats. Thus, the drug treatments did not alter the course of development of cortical monoamine levels. These data suggest that postnatal exposure to the GABA agonist muscimol disturbs specifically the development of hypothalamic NA system in rats.