Effects of vigabatrin on evoked potentials in dogs.

1. The purpose of this study was to evaluate possible changes in brain morphology and evoked potentials associated with daily administration of 300 mg kg-1 vigabatrin in dogs. 2. Somatosensory evoked potentials (SEP) and auditory evoked potentials (AEP) were recorded at baseline and weekly for 12 weeks of treatment and every 2 weeks for 17 weeks of recovery. Morphology was assessed immediately after treatment for two treated dogs and after recovery for the remaining five treated and two control dogs. 3. Vigabatrin produced a significant slowing of the central transmission measure of the SEP with no alteration in the AEP. Vigabatrin was associated with microvacuolation in select regions of the brain including the fornix, septum, optic tract, hypothalamus, thalamus and cortex. In addition, some microglial proliferation was noted. 4. Changes in SEP and the microvacuolation fully recovered after 17 weeks of treatment. 5. The study confirms vigabatrin-induced microvacuolation in the dog and suggests these changes are associated with functional slowing of conduction in the somatosensory pathways.