they found that under the direct impact of stimulating catecholamines ( adrenaline , noradrenalinee , and isoproterenol ) the adrenergic receptors caused increase in spontaneous frequency of heart contractions , as early as in the fifth to ninth weeks of development , that is before adrenergic innervation of the heart .
C0007412
catecholamines
C0022245
isoproterenol