UC Irvine

The inferior colliculus of the genetically epilepsy-prone rat (GEPR) was examined at the ultrastructural level to determine if any abnormalities exist in the inferior colliculus of the GEPR as compared to the non-epileptic Sprague-Dawley rat. Both routine electron microscopic preparations and glutamate decarboxylase (GAD) and GABA immunocytochemical preparations were examined in the GEPR and compared to previous studies from this laboratory that described the normal ultrastructure of the Sprague-Dawley rat. Cell counts from 2 micron semi-thin sections confirmed our previous observations that showed a large, significant increase in the number of neurons in the inferior colliculus of the GEPR as compared to the Sprague-Dawley rat. Many of the small neurons in the inferior colliculus of the GEPR were found to be smaller than those in the inferior colliculus of the Sprague-Dawley rat. Moreover, the small neurons in the GEPR were frequently clumped in clusters of 3-5. Several ultrastructural abnormalities present in the inferior colliculus of the GEPR have been observed at epileptic foci or in brain regions along the pathway of seizure spread in other experimental models of epilepsy. These changes included the presence of dendrites which are almost completely devoid of organelles, hypertrophy of glial processes, and terminals that contain either swollen vesicles or very few vesicles. Other features that were frequently observed in the GEPR but were rarely found in preparations of Sprague-Dawley rats included an abundance of extra membranes, whorl bodies and multivesicular bodies within somata, dendrites and axons.(ABSTRACT TRUNCATED AT 250 WORDS)