To clarify the involvement of neurotransmitters in the remote metabolic effect following focal ischaemia, amino acid neurotransmitter candidates--GABA, aspartate and glutamate--were measured time-sequentially in the basal ganglia following middle cerebral artery occlusion in the rat, which is known to produce a change in glucose metabolism and blood flow in the remote basal ganglia. GABA and aspartate content decreased in the ipsilateral substantia nigra from the second to the 28 th postoperative day. The same tendency was observed in the ipsilateral globus pallidus. Glutamate did not change significantly in either nucleus. In the contralateral side, GABA increased significantly in the substantia nigra throughout the experimental period and in the striatum during the first seven days. These results indicate that the destruction of strionigral tract by focal ischaemia induced the decrease of inhibitory GABA in the ipsilateral substantia nigra. The increase of metabolism in this nucleus may be caused by the decrease of the inhibitory effect.