Immunohistochemical study of pseudohypertrophy of the inferior olivary nucleus

Objective: Pathogenesis of pseudohypertrophy of the inferior olivary nucleus (PH-IO) was analyzed based on immunohistochemical study. Methods. Immunostained medullas with PH-IO were observed with confocal laser microscopy. Results: alpha B-crystallin (alpha BC) was frequently expressed in the neurons and co-localized with microtubule-associated protein 2 (MAP2). The neurons were occasionally positive for SMI-31. alpha BC and SMI-31 were co-localized in some neurons. Synaptophysin (SYP)-immunoreactive dots were present around MAP2-positive hypertrophic neurons and hypertrophic thick neurites. Periphery-stained Lys-Asp-Glu-Leu (KDEL)-positive neurons were shown. Central chromatolytic neurons were found with Kluver-Barrera staining, which indicated that the rough endoplasmic reticulum (ER) was distributed to the periphery of the cytoplasm. Conclusions: alpha BC prevents microtubule disassembly and phosphorylation of the neurofilaments under stressful conditions. Our results indicated that alpha BC protected microtubules and neurofilaments in PH-IO. The retrograde transport of KDEL receptors from the Golgi complex to the ER is increased under stressful conditions. We considered that KDEL receptors were retro-transported to ER, and then the ER containing KDEL receptors was distributed to the periphery of the cytoplasm. PH-IO showed various immunohistochemical changes due to trans-synaptic degeneration.