GRAFTING FETAL SUPRACHIASMATIC NUCLEI IN THE HYPOTHALAMUS OF OLD HAMSTERS RESTORES RESPONSIVENESS OF THE CIRCADIAN CLOCK TO A PHASE-SHIFTING STIMULUS

In the present study, 18-25-month-old hamsters free-running in constan t dim light were injected, both before and after receiving fetal graft s containing either cerebellar tissue or the suprachiasmatic nuclei (S CN), with a dose of triazolam given at a time known to reliably phase shift the rhythm of locomotor activity in young hamsters. SCN-grafted animals, but not control animals implanted with fetal cerebellar tissu e, showed a significantly greater response to the phase shifting effec ts of triazolam, demonstrating that at least some age-related changes in the circadian system can be reversed by neuronal transplantation. T hese results raise the possibility that neuropharmacological intervent ions that can simulate the effects of fetal SCN grafts might be useful in the treatment of age-related disorders in circadian function.