Cytochrome reduction coincides with electrical activity in perfused bullfrog brain.

The redox states of cytochromes a(a3), b and c + c1 were continuously measured on the surface of the perfused bullfrog brain with the aid of a scanning spectrophotometer. To correlate with changes of the redox state, electrical activity was simultaneously recorded in the vicinity of the tip of the light guide of the spectrophotometer. In most cases, parallel reduction of the cytochromes was recorded in concordance with burst activity when the third or the fourth dorsal root of the spinal cord was electrically stimulated for 2 min. Recurrent cytochrome reduction and burst activity were produced by stimulation for a longer period, 5 or 10 min. Both the cytochrome reduction and burst activity were abolished when 1 microM tetrodotoxin was added to the perfusing solution. These results suggest that the cytochrome reduction coinciding with electrical activity in the brain may correlate with the Na+-influx followed by the activation of Na+,K+-adenosine triphosphatase in the neurons.