Effect of Glutamic Acid, NaCN and Monoiodoacetic Acid on the Potential Changes of Isolated Toad's Brain

Abstract

1. Spontaneous potential waves from isolated toad's brain had the amplitude of 10 to 50μ V and the frequency of 4 or 5 cycles per second.
2. When glutamic acid was applied to the brain, convulsive waves over 100μ V in amplitude and of 10 to 20 cycles per second were evoked from the hemisphere and the optic lobe. With regard to the threshold concentration of glutamic acid, some local differences were found.
3. The amplitude of spontaneous waves increased in alkaline and decreased in acid Ringer's solutions. At extremely high values of pH such as 11.0 there occurred convulsive waves similar to those evoked by glutamic acid.
4. NaCN abolished the spontaneous waves in high concentrations, but enhanced them temporarily in low concentrations.
5. Monoiodoacetic acid increased the amplitude of the spontaneous waves in middle concentrations, while no change was seen in higher or lower concentrations.
6. Repeated application of a drop of 1 per cent glutamic acid to the hemisphere at intervals of 10 minutes caused a burst of convulsive waves every time, and such a response could be found till about 2 or 3 hours after excision of the brain. The brain soaked in NaCN, however, soon lost the ability of responding to stimulation with glutamic acid. Monoiodoacetic acid showed a similar effect even in such moderate concentration in which the drug enhanced the spontaneous waves.