Morphological study of experimental cerebral vasospasm. I: Electron microscopic examination of experimental cerebral vasospasm.

Ultrastructural and histochemical changes of experimental vasospasm were studied in 46 cats. Prolonged vasospasm of the exposed basilar artery was produced by continuous irrigation with serotonin. Vasospasm, lasting for less than 10h was relieved by topical application of vasodilators. However, the spasm which continued for more than 10h failed to respond to vasodilators. In the vessels responsive to vasodilators, the electron density of the aggregation of granules and vesicles in the extracellular space of the media revealed by electron microscopy remained unchanged after treatment with 5-hydroxydopamine, while the electron density of the vesicles in adrenergic terminals was increased. The granules and vesicles morphologically resembled the adrenergic vesicles but were biochemically different from them. Necrotic fhanges of the vessel wall such as the fragmentation of myofilaments were observed in the vessels unresponsive to vasodilators. The potassium pyroanitimonate staining technique revealed fine deposits with-in the nucleus, sarcoplasm, sarcoplasmic reticulum and mitochondria, and along sarcolemma in normal vesels. The deposits were shown to contain calcium by X-ray microanalysis and EGTA-chelation. The deposits along the sarcolemma decreased in number in the lanthanum-loaded vessels, and most of them were confirmed to reside on the outer surface of sarcolemma. The calcium deposits increased somewhat in number in the sarcoplasm of spastic vessels responsive to vasodilators, but the deposits along the sarcolemma remained unchanged. The most characteristic change was that calcium along the sarcolemma had disappeared in the spastic vessels unresponsive to vasodilators.