[Axonal transport blockage by acute intraocular pressure elevation in monkeys]

Abstract

The distribution of orthograde rapid axonal transport blockage in the optic nerve head by acute intraocular pressure (IOP) elevation in monkeys was studied by autoradiography. Tritiated leucine was injected intravenously two hours before IOP elevation, and the IOP was elevated for five hours, maintaining a perfusion pressure of 30mmHg. Serial step cross sections from the optic nerve head at the level of the lamina cribrosa were prepared for light microscopic autoradiography, and the accumulation and distribution of grains were quantitatively analyzed using computerized image analysis. The area of focal grain accumulation was expressed as a percent of the defined optic nerve area and each eight sectors, divided by axially intersecting vertical, horizontal, and diagonal lines, respectively. In eyes with IOP elevation, the mean area of focal accumulation of grains in the temporal half of the optic nerve was significantly larger, compared with the nasal half. Within axonal bundles, the focal high accumulation of grains was frequently identified to be in association with trabecular beams of connective tissue in the peripheral portion of the axonal bundle. These results suggest temporal dominant blockage of axonal transport in the optic nerve head, which may be induced by mechanical compression of the axonal bundles during IOP elevation.