A High‐Affinity, Na+‐Dependent Uptake System for γ‐Hydroxybutyrate in Membrane Vesicles Prepared from Rat Brain

Abstract

γ-Hydroxybutyrate (GHB) is a compound with numerous neuropharmacological properties. The discovery of its biosynthetic system, together with its endogenous repartition, have prompted its possible implication in neurotransmission. This role is also supported by the existence, reported here, of a high-affinity uptake system for GHB (K_m= 46.4 μM)in both purified brain plasma membrane vesicles and in the crude mitochondrial fraction. GHB uptake is dependent on a Na⁺ gradient but is independent of the membrane electrical potential. Cl⁻ and K⁺ can also modulate the uptake. As an approach to determine the conformation required for GHB uptake, a series of related compounds, including aryl-or alkyl-derivatives, has been examined for ability to inhibit GHB uptake. The regional distribution of uptake is also indicative of its possible physiological role, since in striatum, an area where GHB has a known pharmacological effect on dopaminergic neurons, this uptake activity is the highest.