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Visual evoked potential abnormalities in jaundiced Gunn rats treated with sulfadimethoxine
S Silver1, H Sohmer, J Kapitulnik
1Department of Physiology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Insights
Sulfadimethoxine (SDM) exacerbates bilirubin encephalopathy in jaundiced rats, causing significant visual evoked potential (VEP) changes. Retinal damage (ERG) appeared later, suggesting primary visual pathway injury beyond the retina.
Area of Science:
- Neuroscience
- Toxicology
- Ophthalmology
Background:
- Bilirubin encephalopathy affects the visual pathway, causing paralysis and perception disturbances.
- Jaundiced Gunn rats (jj) exhibit developmental differences in visual evoked potential (VEP) patterns.
Purpose of the Study:
- To investigate the impact of sulfadimethoxine (SDM) on VEP and electroretinogram (ERG) in young jaundiced rats.
- To determine if SDM alters bilirubin distribution and visual pathway function.
Main Methods:
- Administered SDM to 3-week-old jaundiced rats.
- Recorded VEP and ERG to assess visual pathway and retinal function.
- Analyzed changes in wave latency and amplitude.
Main Results:
- SDM caused significant VEP latency prolongations (11-20%) and amplitude reductions (20-64%) within 2-6 hours.
- Electoretinogram (ERG) changes, specifically prolonged wave b, were observed 6 hours post-injection.
- VEP alterations occurred earlier and were more pronounced than ERG changes.
Conclusions:
- SDM administration significantly impacts the visual evoked potential in hyperbilirubinemic rats.
- The primary site of bilirubin-induced damage in the visual pathway appears to be beyond the retina.
- Early VEP changes suggest rapid neurotoxicity in the brain following SDM-induced bilirubin displacement.
Abstract:
The manifestations of bilirubin encephalopathy include disturbances in the visual pathway (visual gaze paralysis and distorted visual perception). In the young jaundiced Gunn rat (jj) model of hyperbilirubinemia, significant differences in visual evoked potential (VEP) patterns have been recorded during development. In the present study, the effects of sulfadimethoxine (SDM) on VEP and electroretinogram (ERG) were examined in 3-wk-old jj rats. This drug displaces bilirubin from its albumin binding sites in the circulation, shifting it into tissues including the brain. Marked latency prolongations (11-20%) and reduced amplitudes (20-64%) were observed in the different wave components of the VEP. These changes were evident as early as 2 h after injection of the drug and persisted thereafter for another 4 h. On the other hand, ERG changes (significant prolongation of wave b) became apparent in these animals only 6 h after SDM injection. These results suggest that, although some changes in the retina may occur after a massive entry of bilirubin into the nervous system, the primary damage in the visual pathway after bilirubin exposure is probably beyond the retina.