Summary 1. In mice reserpine decreased the γ-amino butyric acid content of brain as well as the threshold for electroshock seizures. Iproniazid increased the GABA content and normalized the lowered GABA level and the lowered threshold for electroshock after reserpine. 2. The glycogen content of brain, liver, heart and skeletal muscle over a period of 18 hr was significantly increased after pretreatment with reserpine. At the same time lactic acid in brain decreased. 3. The increase of glycogen content in brain and liver produced by reserpine probably is due to an enhanced gluconeogenesis. This view is supported by an enhanced incorporation of radioactivity derived from U- 14C-aianine in both organs. 4. Whereas gluconeogenesis in liver is accompanied by a rapid influx of C 14-α-amino isobutyric acid, the influx into brain is significantly lowered after pretreatment with reserpine. Contrary to reserpine iproniazid enhanced C 14-α-amino isobutyric acid transfer into brain. 5. Since AIB is actively concentrated by brain both drugs seem to have opposite actions on active transport mechanisms. This perhaps could explain also the opposite resp. antagonistic actions of reserpine and iproniazid on the γ-amino butyric acid content in brain.