Workshop of the 14th Annual Meeting of the Society
Changes in Electroretinogram induced by Ethambutol and Sodium iodate in Dogs
1995 Volume 14 Issue 3-4 Pages 3-4_151-3-4_159
Details
1995 Volume 14 Issue 3-4 Pages 3-4_151-3-4_159
To objectively evaluate the progress of injury caused by visual disorder-inducing drugs and recovery from injury in dogs, an electroretinogram (ERG) was taken without any general anesthetic agent, and the effects on the a-wave, b-wave, and oscillatory potential were examined.
Ethambutol and sodium iodate were used as visual disorder-inducing drugs. Each drug was dissolved in physiological saline (J. P. grade). Ethambutol was administered subcutaneously into the rear dorsal skin at a daily dose of 250 mg/kg for 4 consecutive weeks. Sodium iodate was injected into the cephalic vein of the foreleg once.
Electroretinography was performed without using any anesthetic or restricting the animals. ERGs were taken before administration, and on the 5th, 7th, 14th, 21st and 28th day of administration in the case of ethambutol, and before administration and 1, 3, 5, 24, 48 and 72 hours after administration in the case of sodium iodate, using a recorder for induced reactions. Photo-stimulation was carried out once for each ERG using a xenon lamp at a stimulating intensity of 20 joules 30 cm in front of the eye. The time constant was set at 0.3 and 0.003 sec. The fundus of each eye was examined at the time of the ERG.
With repeated subcutaneous administration of ethambutol, no clear changes in ERG were observed during the administration period, but decoloration of the tapetum lucidum was observed with funduscopy from the 5th day of administration.
In the case of single intravenous injection of sodium iodate, decreases in the amplitude of a- and b-waves appeared 1 hour after administration, and each wave reached its minimum 48 - 72 hours after administration, then gradually returned toward the baseline. Oscillatory potential showed changes similar to those of a- and b-waves, but the course of their recovery was not clear. In addition, partial discoloration of the tapetum lucidum was observed by funduscopy from 24 hours after administration.
