Factor I and γ-Aminobutyric Acid

Abstract

EXTRACTS of brain and spinal cord of mammals inhibit impulse generation in stretch receptor neurons of the crayfish¹. The substance or substances responsible for this action has been referred to as Factor I¹. In mammals this factor is present only in the central nervous system^1,2. Partially purified preparations of the Factor have been found to imitate the action of inhibitory neurons in crustaceans^1,3 and to block synaptic transmission in autonomic ganglia² and monosynaptic spinal reflexes⁴ of mammals. Factor I preparations were also found to activate the hypoglossal nucleus and often to stimulate polysynaptic spinal reflexes⁴. The inhibitory effects of Factor I in the spinal cord could be prevented by a subconvulsive dose of strychnine⁴. Partial purifications of Factor I have been obtained^1,2,4 by taking advantage of the observations that the factor is thermostable, dialysable, stable to acid and alkali, not precipitated by lead acetate or perchloric acid, soluble in methanol, moderately soluble in ethanol and insoluble in other organic solvents.