LOSS OF GABA, BINDING-SITES IN THE CEREBRAL-CORTEX OF RATS WITH ACUTE HEPATIC-ENCEPHALOPATHY

The binding of [H-3]GABA to GABA(A) and GABA(B) binding sites was measured in cerebral cortical membranes derived from control rats and rats with acute hepatic encephalopathy (HE) induced with a hepatotoxin, thioacetamide. HE did not affect the kinetic parameters (K-D and B-max) for the GABA(A) binding site. However, HE decreased B-max (but not K-D) for the GABA(B) binding site to 32% of the control level, indicating a substantial loss of GABA(B) receptors. Since GABA(B) receptors control the cerebral cortical release of the amino acid neurotransmitters glutamate and GABA, the loss of GABA(B) receptors is likely to contribute to the array of disturbances of glutamatergic and GABAergic neurotransmission known to accompany HE.