SUSTAINED CHANGES IN ACETYLCHOLINE AND AMINO-ACID CONTENTS OF BRAIN-REGIONS FOLLOWING MICROSPHERE EMBOLISM IN RATS

The present study was undertaken to explore changes in neurotransmitte rs and neuromodulators of brain regions impaired by microsphere emboli sm-induced, sustained ischemia. Nine hundred microspheres (48 mum) wer e injected into the right internal carotid artery of rats, and the tim e course of changes in the triphenyltetrazolium chloride (TTC)-stained areas of their brain slices and acetylcholine and amino acid contents in the cerebral cortex, striatum and hippocampus of both hemispheres were determined. The TTC-unstained area, a measure of infarction, was developed in the right hemisphere by the 3rd day after the embolism, w hich was similar to that on the 28th day. A marked decline in acetylch oline content of these three regions of the right hemisphere was detec ted throughout the experiment (28 days). The glutamate, aspartate, GAB A, and taurine levels were markedly decreased following microsphere-em bolism. Most of these decreases were significantly attenuated during t he first 5 days following the embolism, and they then partially recove red with time after the operation. Minor metabolic changes were observ ed in the left hemisphere. The results suggest that microsphere-emboli sm induces cerebral infarction and/or sustained damage to acetylcholin e and neurotransmitter amino acid synthesis and/or catabolism of the b rain regions. This model may provide information concerning the pathop hysiological alterations in long-term cerebral ischemia and infarction .