Electroretinographic and electro-oculographic studies were made in pigmented rabbits after the administrations of chloroquine hydrochloride (Aralen).
Systemic administration of chloroquine, 15 mg/kg daily for 20 days, induced marked general weakness, weight loss and even death of animals. EOG and ERG data obtained in survived 6 animals showed nothing abnormal. Azide sensitive DC potential of the eye increased as normal animals did by intravenous administration of 1mg sodium azide. Histopathological studies revealed slight thickening of ganglion cell and nerve fiber layers, with slight irregularity of pigment distribution in pigment epithelium of the retina, photoreceptors and bipolar cells being undisturbed.
Acute experiment in 4 animals with. intravitreal injection of 5 mg chloroquine in 0. 1 ml saline produced marked reduction of scotopic b- potential during the first 2-3 days and this subnormal state remained thereafter. Scotopic a-potential also decreased with lesser degree. Photopic ERG extinguished on the next day, and showed slight recovery after 5 days. EOG data revealed general flattening, of EOG curves and reduced light peak/dark trough ratio throughout the experimental period. Azide reaction, however, was within normal limits 20 days after the treatment. Histological section disclosed marked destruction of ganglion cell and nerve fiber layers, depigmentation and pigment clumping in pigment epithelium, pigment migration into the inner retinal layers, degeneration of visual cells and bipolar cells.
These findings suggest direct toxic action of chloroquine on the retinal tissues with little impairment of functions of pigment epithelium of the retina.
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