LITHIUM LENGTHENS THE PERIOD OF CIRCADIAN-RHYTHMS IN LESIONED HAMSTERS BEARING SCN GRAFTS

Lithium lengthens the free-running period of circadian rhythms in a wi de variety of organisms. The object of the present study was to examin e the effects of lithium treatment on free-running activity rhythms in suprachiasmatic nuclei lesioned (SCN-X) hamsters that had recovered c ircadian rhythmicity following transplantation of fetal anterior hypot halamic grafts containing the suprachiasmatic nuclei (SCN). The animal s were housed individually in cages equipped with running wheels, and locomotor activity was monitored using a computer-based data acquisiti on system. At the end of the behavioral tests, animals were anesthetiz ed and perfused. Brain sections were immunostained for vasoactive inte stinal peptide (VIP) and vasopressin-associated neurophysin (NP) to ev aluate the extent of the lesion and the presence of afunctional graft. In both intact and in SCN-X grafted animals, lithium lengthened the p eriod of free running activity without affecting the amount of activit y or the precision of the rhythm.