MICROSPHERE EMBOLISM-INDUCED CHANGES IN NORADRENALINE RELEASE IN THE CEREBRAL-CORTEX IN RATS

The present study was undertaken to elucidate pathophysiological chang es in noradrenaline release, phosphorylation of synapsin I and ultrast ructure of the cerebrocortical nerve terminals following microsphere e mbolism in rats. In the microdialysis study, K+-stimulated noradrenali ne release in the cerebral cortex was not altered on the Ist day but m arkedly decreased on the 3rd and 7th days after the embolism. Synaptos omes were isolated from the cerebral cortex of the operated animals on the Ist, 3rd and 7th days after the embolism. The level of calmodulin and the phosphorylation of synapsin I in the synaptosomes were not al tered up to the 7th day, but the levels of calcium/calmodulin-dependen t protein kinase IT and synapsin I in the synaptosomes were significan tly decreased by microsphere embolism. Electron microscopic study show ed no appreciable changes in the structure of the synaptosomes on the Ist day, but a large number of clumps of synaptic vesicles were observ ed on the 3rd and 7th days after the embolism. These results suggest t hat microsphere embolism-induced changes in noradrenaline release from nerve terminals are due to a failure in the process following phospho rylation of synapsin I. Aggregation of synaptic vesicles in nerve term inals may contribute to the pathogenesis of microsphere embolism. (C) 1998 Elsevier Science B.V.