An electron microscopic study on the blood-optic nerve and fluid-optic nerve barrier

Abstract

Utilizing horseradish peroxidase as a tracer, electron microscopic studies were done on the blood-optic nerve and fluid-optic nerve barrier to the peroxidase diffusion. Following intravenous injection the peroxidase was observed to fill the lumen of the capillaries of the laminar, prelaminar and orbital portions of the optic nerve but there was no penetratation of the capillary walls. The obstruction of the tracer diffusion out of capillary walls was attributed to the tight junctions between the endothelial cells. Peroxidase penetration was also absent in the capillaries of the pia and dura mater, however, was observed in pinocytotic vesicles of the endothelial cells. Lateral diffusion from the surrounding choroid into the optic nerve was detected but diffusion from the prelaminar optic nerve into the juxta-optic nerve retina was prevented by the Kuhnt intermediary tissue. Tight junctions which prevented peroxidase diffusion were found between the glial cells of the Kuhnt tissue, and this tissue was the barrier between the prelaminar optic nerve and the juxta-optic nerve retina. Peroxidase which was given into the lateral ventricle of the brain appeared in the subarachnoidal space around the optic nerve and penetrated freely into the optic nerve. The pial surface of the optic nerve possess no barrier activity. Peroxidase could be traced along the intercellular space between glial cells and optic nerve fibers. The basal lamina of the optic nerve capillaries was filled with peroxidase but diffusion into the capillary lumen was obstructured by the tight junctions between the endothelial cells.

Chemoarchitecture of glial fibrillary acidic protein (GFAP) and glutamine synthetase in the rat optic nerve: An immunohistochemical study

“…horseradish peroxidase and lanthanum nitrate) from the choroid into the optic nerve was observed, whereas the penetration of these tracers from the optic nerve into the retina was hardly seen [45][46] .…”

Evidence for Cerebrospinal Fluid Entry Into the Optic Nerve via a Glymphatic Pathway

“…These findings build on early work in which tracers injected into the CSF were noted in the optic nerve. [10][11][12] Previously, diaminoacridine dyes 11 (469 Da), sodium fluorescein 10 (376 Da), or horseradish peroxidase 12 (44 kDa) were injected into CSF and found diffusely throughout the optic nerve. These studies were conducted in rabbit, 11 cat, 11 dog, 11 guinea pig, 11 rhesus monkey, 10,11 and mouse.…”

“…[10][11][12] In the brain, a glymphatic pathway has been described in which CSF flows into and out of the parenchyma along spaces formed between blood vessels and an ensheathing layer of astrocytic endfeet. 13,14 The glymphatic pathway consists of paravascular inflow of CSF into brain parenchyma and clearance of fluid and extracellular solutes from the interstitium.…”

Effects of chronic upper respiratory bypass cannula on the morphology and function of the eye of the sheep

“…For example, Rodriguez-Peralta (1963) injected diaminoacridine dye into the cisterna magna of rabbits, cats, guinea pigs, and rhesus monkeys and, after one hour, observed a high con centration of the dye in the subarachnoid space of the optic nerve as well as diffusion into the optic nerve, and optic nerve head, including the intermediary tissue of Kuhnt. Similar observations were made by Tsukahara and Yamashita (1975) when they injected horseradish peroxidase in the lateral ventricles of the mice. This free passage and diffusion of cere brospinal fluid from the intracranial subarachnoid to the orbital part may have some influence on the optic nerve pressure up to the area behind the area cribrosa of the sclera, a factor which Hayreh (1978) claimed to play a role in the pathogenesis of edema of the optic nerve head in pri mates.…”

“…In addition, Schaltenbrand and Putnam (1927) reported that the meninges of the central nervous system are freely permeable, which has been confirmed by Brightman and Reese (1969) and Waggenner (1964). Further, the free passages of materials from the cerebrospinal fluid into the optic nerve sheath, optic nerve, and optic nerve head up to the intermediary tissue of Kuhnt were demonstrated by Rodriguez-Peralta (1963) in rabbits, cats, guinea pigs, and rhesus monkeys; Grayson and Laties (1971) in rats, and Tsukahara and Yamashita (1975) by Krabill (1979) in the sheep during bypass breathing. This also con forms with the findings of Hayreh (1964) (Krabill, 1979) might be responsible for the disc ele vation and its persistence after three days of normal breathing (which will presumably lower the cerebrospinal fluid pressure).…”