Colonic Bacteria: A Source of -Aminobutyric Acid in Blood

Abstract

Blood contains more of the major inhibitory neurotransmitter GABA than does CSF. The source and physiologic importance of this compound in the peripheral circulation are unknown. Blood drawn from the portal vein of normal rabbits contains twice the concentration of GABA as that drawn simultaneously from the abdominal aorta. Human-derived colonic bacteria grown anaerobically secreted a large amount of GABA equivalents into culture media when measured by a radioreceptor technique. The production of inhibitory neuroactive substances such as GABA by colonic bacteria may play a role in the pathogenesis of certain disease states, e.g., hepatic encephalopathy.