Comparison of Na-K ATPase activity in rat brain synaptosome under various conditions

Rapid eye movement (REM) sleep deprivation alters neuronal excitability possibly by increasing Na-K ATPase activity. The enzyme activity is known to be affected by norepinephrine as well as calcium (Ca++) and both are affected by REM sleep deprivation. Before studying its molecular mechanism of action, synaptosomal Na-K ATPase activity was estimated under various conditions. The enzyme activity in synaptosome increased after lysis and in the presence of EDTA. The increase in the lysed preparation was possibly because almost all the active sites of the enzyme molecules were exposed to express their activity, unlike unlysed preparation where half are likely to be inside out. EDTA possibly increased the enzyme activity by chelating the Ca++ which is known to have an inhibitory effect on the enzyme activity. Also, the REM sleep deprivation induced increase in the enzyme activity was observed in lysed preparations and in the presence of EDTA only. These observations fit with the existing knowledge, however, the molecular mechanism of the increase needs to be investigated.