Investigation of circadian rhythms in a genetically anophthalmic mouse strain: Correlation of activity patterns with suprachiasmatic nuclei hypogenesis

Summary ZRDCT-An mice are anophthalmic mutants with varying degrees of hypogenesis of the mediobasal hypothalamus and suprachias-matic nuclei. Statistical analysis of the wheelrunning activity patterns of these animals showed that most mice had circadian activity rhythms unentrained to the light-dark cycle. However, four of 22 animals had random or non-circadian activity patterns. Of these four mice, three had fewer than one third the typical number of cells in the suprachiasmatic nuclei. The absence of detectable circadian rhythms in mice with genetically produced hypogenesis of the suprachiasmatic nuclei is reminiscent of the effects of partial electrolytic lesions of the same tissue.Abbreviations SCN suprachiasmatic nuclei - LD light dark - DD dark-dark