Effect of change in activity level of catecholaminergic systems on motor, respiratory, and cardiac activities in fetal rats

Abstract

Parameters of motor, respiratory and cardiac activities were studied in rat embryos (E17-20) after changes in activity level of catecholaminergic systems. To produce conditions for excessive level of catecholamines, the animal were administered individually with preparation of L-DOPA at doses of 25, 50 and 100 mg/kg. Also studied was action of L-DOPA after blockade of D1-(antagonist - SCH-23390, 0.1 mg/kg), D2-(antagonist - sulpiride, 50 mg/kg) dopaminic, and beta2-(antagonist - propranolol, 1 mg/kg) adrenergic receptors. It was found out in E17-18 that the DOPA administration regardless of dose, while in E19-20 dose-dependently produces continuous generalized activity. Between E18 and E19, ontogenetically new is the appearance in 92 % of embryos of stereotypical head movements (circular movements, lateral and dorso-ventral flexions) following in the nearsecond rhythm. Injection of DOPA to rat embryos increased 2-6 times the number of respiratory movements by the gasping type in E17-20 and decreased the amount of episodes of continuous rhythmical respiration in E19-20. No significant heart rate changes were observed after introduction of DOPA to E17-20. There was noted a tendency for a weak acceleration of the heart rate. The changes in activities of the motor and respiratory systems due to a rise of catecholamine level are not connected with activation of the dopamine system, as they are not reduced by blockade of dopamine receptors.