Altered residual ATP content in rat brain cortex subcellular fractions following status epilepticus induced by lithium and pilocarpine

Changes in residual ATP concentrations were investigated following subcellu lar fractionation of rat brain cortex after a prolonged period of status ep ilepticus induced by sequential administration of lithium and pilocarpine. After 2 h of continuous high-amplitude rapid spiking on EEG, we found signi ficantly decreased levels of residual ATP in the homogenate and mitochondri a fractions from status epilepticus rat brains compared to matched controls . No difference in residual ATP level was observed in the synaptosomal prep arations of status epilepticus animals compared to controls. Inorganic phos phate concentration in the status animals was higher than controls in the c ytosolic fraction only. F1-ATPase activity, an enzymatic indicator of mitoc hondrial ATP synthesis rate, was significantly higher in the status brains, whereas other mitochondrial enzymes were not different in the status and c ontrol rat groups. These findings, together with our earlier report of redu ced synaptosomal ecto-ATPase activity, suggest that either the correspondin g in vivo ATP concentrations were reduced as a result of status epilepticus or other biochemical changes had occurred that facilitated the hydrolysis of ATP following decapitation. Controls for and measurement of such other c hanges failed to provide an explanation for the observed changes in residua l ATP.