Morphological Study of Experimental Cerebral Vasospasm

Canine basilar artery was studied in vivo and in vitro. Cell membranes of vascular smooth muscle were differentiated into caveolae intracellulares zones and caveolae-free zones, both of which were generally arranged in an alternate manner and parallel to the long axis of the smooth muscle cell. The caveolae intracellulares, about 60 nm in diameter, were neatly oriented in one to several rows with a center-to-center distance of about 80 nm. Adherens, gap, and tight junctions were occasionally found in the smooth muscle. In vitro study of canine basilar artery suggested the necessity of extracellular Ca supply for prolonged contraction, and strontium was selectively deposited in sarcoplasmic reticulum and mitochondria. Prolonged vasospasm was produced in the canine basilar artery by the injection of fresh blood or norepinephrine into the chiasmatic cistern. The caveolae intracellulares of vascular smooth muscle were found to be increased in number in vasospasm. In thin sections, myonecrosis was found in a small number of muscle cells, while a large number of muscle cells appeared intact. The most characteristic change was the appearance of aggregated granules and vesicles in the widened extracellular space between smooth muscle cells, particularly in the periphery of muscular layer and beneath the elastic lamina. The granules were spherical, 50-100 nm in diameter and were often surrounded by a single membrane and contained a dense osmiophilic core of about 40-90 nm diameter. In addition, the elastic lamina often became loose and corrugated or broken.