The effect of optic nerve transection upon the hypotensive action of ascorbate and mannitol

Some investigators have suggested that osmolarity agents act on a central neural regulation mechanism rather than producing a direct local effect on the ocular hemodynamics. In this study, a small dose of ascorbate (.15 gm/kg, IV injection) was given to rabbits following unilateral optic nerve transection. The intraocular pressure of both eyes was significantly reduced within 5 minutes with a maximum drop at 10 minutes. When mannitol was given (0.3 gm/kg, intravenous infusion), maximal reduction of intraocular pressure occurred at 30 to 50 minutes in both eyes. In this study, it appears that optic nerve transection did not abolish the ocular response to the hypotensive action of either ascorbate or mannitol. On the contrary, the hypotensive effect of ascorbate was stronger in the experimental eye. The effective time on aqueous humor dynamics of the ascorbate occurred earlier than that of mannitol under similar experimental situations.