Absence of γ-Aminobutyric Acid from Brain Extracts containing Factor I

Abstract

FLOREY¹ and Florey and McLennan^2,3 have described some of the actions of extracts of brain and spinal cord which possess an inhibitory activity on certain synaptic processes, both in mammals and in invertebrate animals. For example, these extracts, which are said to contain ‘Factor I’, can block transmission in sympathetic ganglia, can inhibit monosynaptic reflexes, can block neuromuscular transmission and the neurogenic heartbeat of Crustacea, and can inhibit the discharge of crustacean stretch receptor neurones. Bazemore, Elliott and Florey⁴ have reported that an active component of extracts containing Factor I is γ-aminobutyric acid. Since that time it has been shown that γ-aminobutyric acid does have effects of an inhibitory nature, especially in Crustacea⁵ and when applied to the mammalian cerebral cortex⁶. However, a comparison of the actions of Factor I and γ-aminobutyric acid on those structures where the former is active has shown that, except in Crustacea, the effects obtained with the two are not comparable, and it was concluded that they are not identical⁷.