Ultrastructural morphology of thalamic cytoplasmic inclusion bodies in El mouse.

The established hereditary El mouse, clinically characterized by intermittent seizures of the grand mal type, has been investigated mainly from biochemical or electrophysiologic points of view. The present paper provides morphologic details on neuronal inclusion bodies occurring in the thalamus of the El mouse. Numerous intracytoplasmic inclusion bodies, 1 to 10 microns in diameter, were observed in the thalamic neuronal cells even in the young or seizure-free El mouse. Although such inclusion bodies were also studied in aging normal mice, their number in the El mouse was significantly higher than the number seen in aged mice. In addition to the thalamic inclusions, there were other changes observed, such as hippocampal neuronal loss and ischemic or chromatolytic neurons in the temporal cortex. We suggest that the neuronal changes in hippocampus and cortex were not primary to the El mouse epileptogenesis. We discuss the correlation between thalamic neuronal inclusions and convulsive seizures in the El mouse.