Changes in the norepinephrine and dopamine levels in the hypothalamus and caudate nucleus were studied in reserpinized rabbits after administration of dopa. Injection of dopa into reserpinized rabbits caused a great increase in the dopamine content of the hypothalamus without any noticeable affect on the norepinephrine content. On the other hand, electron microscopic studies demonstrated the reappearance of granulated vesicles with dense cores in the hypothalamus after dopa injection. These findings suggest strongly that the granulated vesicles in the hypothalamus store dopamine as well as norepinephrine. The siginificance of the newly formed dopamine and the granulated vesicles are discussed.
