Effects of formyl tetrahydrofolic acid and noradrenaline on the oxygen consumption of rat brain synaptosome-mitochondrial preparations.

1. The respiration of a mitochondrial and synaptasome fraction of rat cerebral cortex was measured using an oxygen electrode.2. Little or no enhancement of oxygen uptake occurred on separately adding formyl tetrahydrofolate or noradrenaline.3. When these substances were added together a marked increase in respiration was observed.4. Both phenobarbitone and phenytoin inhibited the respiration of this preparation, but this was reversed on the addition of formyl tetrahydrofolate.5. The possibility that some antiepileptic drugs may compete with formyl tetrahydrofolate in the brain is considered and structural similarities between folic acid and these drugs are indicated.