The in vitro action of SP and theophylline on the activities of (Na K) and (Ca Mg) dependent adenosine-5'-triphosphates (ATPase) of crude synaptosomal membranes (SM) of four different areas of rat brain was investigated. The highest activity of (Ca Mg)ATPase was observed in SM from hippocampus. In thalamus with hypothalamus region the highest activity of (Na K)ATPase and the lowest activity of (Ca Mg)ATPase occurred. It was found, that 10 mumol of SP stimulating "alternatively" both (Na K) and (Ca Mg)ATPase activities from different regions may constitute a regulating agent for ionic transport in CNS of rat. Theophylline on concentration of 5 mumol modulates the action of SP on the activities of the investigated enzymes.