The relationship between circadian rhythmicity and vasoactive intestinal polypeptide in the suprachiasmatic nucleus of congenitally anophthalmic mice

To date, the search for the clock component that is both necessary and suff icient for generation of circadian rhythms has relied primarily on experime ntal interventions such as lesions and transplantation of fetal SCN. While these approaches have been fruitful lesions disrupt adjacent host tissue an d fiber pathways, and donor tissue is likewise subject to trauma during har vest and transplantation. The current investigation has used congenitally a nophthalmic (eyeless) mice to ask whether VIP-IR SCN neurons are necessary and sufficient for generation of circadian rhythms. In this animal model, a rrhythmic mice occur naturally, together with their rhythmic littermates. W e have combined recording of wheel-running activity with light microscopic immunocytochemistry for vasoactive intestinal polypeptide (VIP) and cyto ar chitectural analysis of the suprachiasmatic nuclei (SCN) in rhythmic and ar rhythmic anophthalmic mice. Our data provide the first definitive evidence that the presence of VIP neurons in the SCN is not sufficient for generatio n of circadian locomotor rhythms. (C) 2001 Elsevier Science B.V. All rights reserved.