LIGHT-INDUCED PHASE-SHIFTS AND FOS EXPRESSION IN THE HAMSTER CIRCADIAN SYSTEM - THE EFFECTS OF ANESTHETICS

In the present study, we examined the effect of administration of anes thetics on light-induced phase shifts of the circadian system. This in formation is of critical importance, because many studies of light inp ut to the mammalian suprachiasmatic nucleus (SCN) have been performed on anesthetized animals. We found that light-induced phase shifts were blocked by all drugs used at anesthetic doses. We then determined the effect of two of these agents on light induction of Fos-like immunore activity in the SCN. We found that the administration of sodium pentob arbital prevented light induction of Fos expression in the SCN, wherea s the administration of urethane did not. These results raise cautions about the use of anesthetized animals to answer questions about the p hotic regulation of neuronal activity in the SCN.