The cuprizone model for demyelination Introduction Although multiple sclerosis (MS) is exclusively affecting humans, a number of animal models for the disease have been established. The most widely used models are experimental autoimmune enceph- alitis (EAE) (1), TheilerÕs virus-induced encephali- tis (2), and the cuprizone model (3). In EAE, immunization with myelin antigens or passive transfer of myelin-specific T lymphocytes induces an inflammatory demyelination in the central nervous system (CNS) of the animal. In TheilerÕs virus-induced encephalitis, infections of mice with the neurotropic picornavirus TheilerÕs murine encephalomyelitis virus (TMEV) leads to a pro- gressive CD4(+) T-cell-mediated demyelinating disease. The cuprizone model (3) is a model of toxic demyelination. In this model, young adult mice are fed with the copper chelator cuprizone (bis-cyclo- hexanone oxaldihydrazone). This leads to consis- tent demyelination. Spontaneous remyelination can however be observed as early as 4 days after withdrawal of the neurotoxin (4), thus making the cuprizone model excellent for studying factors which can prevent demyelination and stimulate remyelination. Mice strain and cuprizone administration The cuprizone model was first established in Swiss mice (5, 6), but most recent publications have relied on the C57BL ⁄ 6 strain (7, 8). The C57BL ⁄ 6 strain is classified as inbred. This results in an offspring that possesses both genetic and phenotypic unifor- mity. The C57Bl ⁄ 6 strain is today one of the preferred mouse strains for research. Further, the complete genome sequence of this strain has been made available. Thus, the use of C57BL ⁄ 6 mice offers a good potential of using the model in knockout gene studies. The dosage necessary to induce demyelination is strain- and age-dependent (9). The standard protocol applied in the recent years has been feeding 8-weeks-old C57BL ⁄ 6 mice with 0.2% cuprizone (w ⁄ w) for 6 weeks. Lindner et al. (4) have demonstrated that a higher degree of demyelination can be achieved by increasing the dosage to 0.3% cuprizone (w ⁄ w). The major drawback with doing this, is that the mortality rate in the cuprizone mice rises from <5% with Torkildsen Ø, Brunborg LA, Myhr K-M, Bø L. The cuprizone model for demyelination. Acta Neurol Scand 2008: 117 (Suppl. 188): 72–76. Ó 2008 The Authors Journal compilation Ó 2008 Blackwell Munksgaard. Background – Important advances in multiple sclerosis (MS) research have been made as a direct or indirect result of experiments in animal models for the disease, although MS is a disease only affecting humans. The cuprizone model is a model for toxic demyelination. In this model, young mice are fed with the copper chelator cuprizone, leading to oligodendrocyte death and a subsequent reversible demyelination. Spontaneous remyelination can be seen as early as 4 days after withdrawal of cuprizone. Materials and methods – This article reviews previous research on this model and discusses the potential of the model for future application in MS research. Discussion – The cuprizone model correlates with newer histopathological data in MS and is a valuable tool for studies on de- and remyelination. The use of the C57BL ⁄ 6 strain offers the potential for future studies on transgene and knockout mice. Ø. Torkildsen 1,2 , L. A. Brunborg 3 , K.-M. Myhr 1,2 , L. Bø 1,2 1 Norwegian Multiple Sclerosis Competence Centre, Department of Neurology, Haukeland University Hospital, Norway; 2 Department of Clinical Medicine, Section for Neurology, University of Bergen, Norway; 3 National Institute of Nutrition and Seafood Research (NIFES), Nordnes, Bergen, Norway Key words: cuprizone; demyelination; multiple sclerosis Øivind Torkildsen, Department of Neurology, Haukeland University Hospital, N-5021 Bergen, Norway Tel: +47 55 97 70 39 Fax: +47 55 97 59 01 e-mail: oivind.torkildsen@gmail.com Conflict of Interest: The authors declare no conflict of interests. Acta Neurol Scand 2008: 117 (Suppl. 188): 72–76 Copyright Ó 2008 The Authors Journal compilation Ó 2008 Blackwell Munksgaard ACTA NEUROLOGICA SCANDINAVICA 72