Increased capillary permeability of the stria vascularis to HRP, induced by experimental acute hypotension in rats.

Acute hypotension was produced in rats by using two experimental techniques: intravenous infusion of a ganglion-blocking agent (Arfonad), and venesection of a femoral vein. Horseradish peroxidase (HRP) was injected intravenously after each procedure, and subsequently observed in the inner ear by light and electron microscopy. In both experimental models, a large amount of tracer spread into the intercellular spaces, but it was halted by tight junctions bordering the stria vascularis. The endothelium exhibited a high distribution density of labelled vesicles, which suggested increased vesicular transport. There was no extravasation of HRP from capillaries in the spiral ligament in spite of the presence of some labelled pinocytotic vesicles. The present study was concerned with the discovery of enhanced capillary permeability of the stria vascularis under acute hypotension, as in the case of acute hypertension (Sakagami et al., 1984).