Change in character of motor, respiratory, and cardiac activities in rat embryos at stimulation of release of endogenous catecholamines

To solve the problem of functional efficiency of endogenous catecholamines in embryos, we used in this study the indirect adrenomimetic isoamine whose action is associated with their release, suppression of reuptake, and inhibition of monoamine oxidase. Results establish that as early as at E17E18 the level of endogenous catecholamines is sufficient for change both of motor and of respiratory activity. With development, there occurs transition from the exclusively activating isoamine action in the younger fetal group to the appearance of cases of the pronounced inhibition at E19 E20. The pharmacological analysis with use of blockers of D1- and D2-dopamine receptors has shown that the observed effect of introduction of isoamine on the fetal motor activity probably are not associated with activation of the dopaminergic system, whereas effect of the latter on fetal respiration is not excluded.