[Adrenergic mechanisms regulating the motor reactions of rats in the early postnatal period].

In 12-day-old rats, L-DOPA, a precursor of catecholamine synthesis, provokes an increase in the rate of the motor reactions (MR) of the shudder type. Reserpine which promotes catecholamine release from the tissues, leads to the diminution of the rate of the MR of the shudder type in rats of the same age. Aminazine, an alpha-adrenoblocker and antagonist of dopamine receptors, decreases the rate of the MR of the shudder type. Administration of aminazine in a dose of 10 mg/kg at different age periods produces inconclusive changes in the diminution of the rate of the MR of the shudder type. During sudden changes in the growth, the rate of the above-described modulations substantially decreases. The high rate of the MR of the shudder type seen in rats in the early postnatal period is a consequence of the marked activity of the catecholaminergic (dopaminergic) systems during that period. Reduction in the effect of the decreased MR rate produced by the same dose of aminazine during the critical periods of the growth also attests to the high activity of the catecholaminergic (dopaminergic) system in rats at that period.