The minute vessels of the cochlea were examined post mortem in normal guinea pigs and in others exposed to intense noise or treated with the ototoxic drugs gentamicin and quinine. The benzidine stain was used to display the capillary networks, and osmic acid for surface preparations, “thick” sections, and ultrathin sections for electron microscopic examination.
The capillaries of the spiral ligament, i.e., the so-called arteriovenous anastomoses, do not show the characteristics of the muscular shunts described by Chambers and Zweifach. They are divided into two groups, the adstrial capillaries closely applied to the basal surface of the stria vascularis, and the poststrial capillaries which supply the tissue of the spiral ligament. Continuing beneath the floor of the external sulcus they form an alternating pattern with the root cells, and are surrounded by a specialized pericapillary tissue which resembles that found around the capillaries of the spiral prominence. These tissues are readily destroyed by gentamicin and other ototoxic aminoglycosidic antibiotics.
Vasoconstriction of the outer and inner spiral vessels in response to noise and quinine appears to involve both contraction of pericytes and swelling of the endothelial cells. After prolonged exposure to noise or treatment with gentamicin, degeneration of capillaries with formation of intervascular strands and avascular channels is found in the suprastrial network of the spiral ligament. Similar capillary changes are seen in presbycusis, and in the deaf Dalmatian dog.