Nevertheless, the molecular mechanism of leucine-dependent activation of mTORC1, resulting in enhanced protein synthesis in the neonate, has not been completely studied. Therefore, our study aimed to determine the molecular mechanism by which leucine modulates mTORC1 activation and protein synthesis in skeletal muscle with different fiber types, represented by gastrocnemius and masseter muscles, and in visceral tissues, represented by the liver, using rapamycin as an mTORC1 blocker.