The morphology of spastic intracerebral arterioles.

Pial and parenchymatous vessels of cat cerebral cortex were subjected to electrical stimulation by direct current by the application of a silver gel electrode to the vessel wall. A current of small intensity (5V, 10mA, 2s) was sufficient to produce spastic constriction of the pial arteries. Arterial spasm was always segmental and lasted up to 20 min. Intracerebral vessels were stimulated by applying a DC of 20 to 100 V, 20 to 150 mA for 30 s to the brain. Intracerebral muscular vessels showed varying diameters and spastic segments in frozen sections and by electron microscopy. The lumen of spastic vessels was collapsed. The vessel wall convoluted, indicating that the factors causing spastic constriction are different from those responsible for physiological vessel wall constriction. In many cases the perivascular tissue of moderately constricted or spastic arterial vessels was destroyed while the tissue around capillaries always remained intact. It is suggested that periarterial tissue destruction is the result of the sudden and powerful constriction in muscular arteries.