FREE GABA, GABA CONJUGATES AND HOMOCARNOSINE IN CSF: RELATIONSHIP TO BRAIN GABA

Abstract

Publisher Summary This chapter discusses free GABA, GABA conjugates, and homocarnosine in cerebrospinal fluid (CSF). GABA is found in the CSF of several animal species and man in very small amounts as the free amino-acid (65, 61, and 220 pmol/ml for rats, cats and humans respectively). GABA also exists in conjugated forms, mainly as homoearnosine. In contrast to the low concentrations of free GABA, conjugated GABA is found in considerably higher concentrations. If the concentration of brain GABA is elevated in experimental animals by the inhibition of GABA-transaminase with γ-acetylenic or γ-vinyl GABA, there is a significant dose and time-related elevation in both the free and total conjugated GABA and in homocarnosine concentrations found in the CSF. In rats, brain GABA concentrations correlated linearly with both total GABA conjugates and homocarnosine. An analysis of the dynamics of accumulation of free and conjugated GABA in the CSF following the pharmacological alteration of brain GABA suggests that conjugation may be a mechanism for maintaining free GABA concentrations in the CSF at a minimum level.