| Popis: |
The effects of adrenaline and other adrenergic drugs on the isolated, electrically driven ventricles and ventricular strips from the tadpoles, the first year froglets and adult frogs have been studied. Adrenaline induced positive inotropic effect at all developmental stages including the earliest one, stage 32 (stages were determined according to Dabagian and Sleptsova). The pharmacological analysis revealed the beta-adrenergic origin of this effect. The sensitivity to adrenaline decreased after the stage 43 and became the lowest in adult hearts. It may partly be due to maturing of the neuronal uptake mechanism because the sensitivity to isoproterenol which is not subjected to the neuronal uptake processes was not decreased in the adults as compared to tadpoles. The adrenoceptors of the tadpole heart have the higher affinity to propranolol then the adrenoceptors of the adult heart. |
