Ultracytochemical study on the oxidoreductase activity in synapses in the rat cerebral cortex

The copper ferrocyanide method recently developed in our laboratory for the ultracytochemical demonstration of oxidoreductases was applied in the rat cerebrum. It was found that ferricyanide was reduced in synaptic membranes of both vesiculated and non-vesiculated bags, the synaptic cleft and membranes covering non-vesiculated bags in synapses, and in membranes of the neuronal perikaryon as well as processes including axons, when sodium succinate and cytochrome c were used as substrate. Some mitochondria in non-vesiculated bags of synapses and in the neuronal perikayron as well as processes also showed the reaction product. Based on control studies performed it was postulated that the oxidoreductase activity seen in membranes was due mainly to the cytochrome c-ferricyanide reductase.