Biol. Pharm. Bull. 28(4) 615—618 (2005)

model of accelerated aging symptoms established by Takeda et al. SAM is composed of eight aging-prone (SAMP) lines and three resistant (SAMR) lines. SAMP8 shows marked impairment of learning and memory. We previously reported several neurochemical alterations in the hippocampus of aged SAMP8 such as i) the elevated amounts of glutamate and glutamine in the hippocampus, ii) the decreased release of acetylcholine and noradrenaline in comparison to agematched controls from strain SAMR1. Yagi et al . reported that the spongy degeneration in the brain stem of aged SAMP8 in histological analysis. They also reported that vacuolization in the brain stem was caused by changes to both oligodendrocytes and neural cell dendrites. Recently, it has been shown that expression of pro-inflammatory cytokines, such as interleukin 1-b (IL1-b), interleukin-6 (IL-6) and tumor necrosis factor-a (TNF-a) was elevated in the SAMP8 brain. The oligodendrocytes are vulnerable to various factors that can easily cause cell death, including inflammatory cytokines, viruses and brain-blood barrier disruption. An immunohistochemical study revealed that the activation of astrocytes and microglia occurred in the hippocampal CA1 subfield in addition to the brain stem of aged SAMP8 however, the changes in oligodendrocytes in the hippocampus of aged SAMP8 are still unknown. Myelin basic protein (MBP) is a protein accounting for approximately 30% of the total protein of myelin, and it is localized in the myelin and cell body of oligodendrocytes. 2 ,3 -cyclic nucleotide 3 -phosphodiesterase (CNP) is an enzyme protein accounting for approximately 4% of the total myelin protein, and it is localized in the cell body and involved in oligodendrocyte processes, although its physiological role is not yet understood. Melcangi et al. reported that the MBP-IR in the sciatic nerve was markedly decreased in normal aging. In the present study, we examined the changes in oligodendrocytes in the brain of SAMP8, using MBP and CNP as an oligodendrocyte marker. MATERIALS AND METHODS