SPONTANEOUS RHYTHM IN C-FOS IMMUNOREACTIVITY IN THE DORSOMEDIAL PART OF THE RAT SUPRACHIASMATIC NUCLEUS

In rats maintained for 2 days in constant darkness, the suprachiasmati c nucleus exhibited a circadian rhythm in c-Fos immunoreactivity, with the maximum in the morning and trough during the subjective night. In contrast to the night-time photic c-Fos induction occurring in the ve ntrolateral part of the nucleus, the spontaneous rhythmic c-Fos induct ion in darkness occurred in the dorsomedial part and might indicate an elevated dorsomedial neuronal activity in the early subjective day. ( C) 1998 Published by Elsevier Science B.V. All rights reserved.