Aconite is a common remedy of herb doctors and is widely used in the Far East. Clinical aspects of the visual disturbance produced by this drug have been described, but little is known about its pathology. Tinctura aconiti (0.6 mg of total alkaloid/kg 2x) was administered intraperitoneally in rabbits to evaluate its toxic effects on the visual system. The alteration in the visual evoked potential following aconite injection consisted of a delay in the onset and peak latency. Histopathologically, there were damages to the myelin sheath of the visual pathway, spinal cord and peripheral nerves. These findings suggest that aconite may cause primarily myelo-optic neuropathy.
Aconitum/administration & dosage/*toxicity ; Animals ; Evoked Potentials, Visual/*drug effects ; Injections, Intraperitoneal ; Myelin Sheath/*drug effects/ultrastructure ; Optic Nerve/*drug effects/ultrastructure ; Optic Nerve Diseases/*chemically induced/pathology ; Rabbits ; Spinal Cord/*drug effects/ultrastructure

The purpose of this study was to evaluate the neuroprotective effect of memantine, a N-methyl-D-aspartate antagonist, in an experimental optic nerve ischemia. Endothelin-1 (ET-1) in a dosage of 0.1 microg/day was delivered to the perineural region of the anterior optic nerve by osmotically driven minipumps for 8 weeks in 10 rabbits. In 5 rabbits, 1 mg/kg memantine was administered concurrently by intramuscular injection once a daily. Morphologic optic nerve head changes were monitored with a confocal scanning laser ophthalmoscope. Multivariate statistical analysis showed a significant change in topometric parameters (cup area, cup depth and rim volume), indicating an increase in optic nerve head cupping and a decrease of neural rim volume in the ET-1 administered eyes (P < 0.0001). In rabbits where memantine was given concurrently with ET-1, no significant change in topometric parameters was observed after ET-1 administration (P = 0.78). The current results suggest that memantine has a neuroprotective effect in optic nerve ischemia. Memantine may potentially be useful in the management of various ischemic disorders of the optic nerve, including glaucoma.
Animal ; Comparative Study ; Endothelin-1/toxicity ; Excitatory Amino Acid Antagonists/*therapeutic use ; Male ; Memantine/*therapeutic use ; Models, Animal ; Neuroprotective Agents/*therapeutic use ; Optic Disk/*drug effects/pathology ; Optic Nerve/*drug effects/pathology ; Optic Neuropathy, Ischemic/chemically induced/pathology/*prevention & control ; Rabbits