EFFECTS OF BILATERAL OLFACTORY BULBECTOMY ON CIRCADIAN-RHYTHMS OF ACTH, CORTICOSTERONE, MOTOR-ACTIVITY AND BODY-TEMPERATURE IN MALE RATS

Bilateral olfactory bulbectomy (BOX) has major biochemical and behavio ral effects, and is one of the most widely investigated of animal mode ls of depression. We studied the consequences of BOX in male rats, an the organization of endogenous circadian rhythms for ACTH, corticoster one (Cort), motor activity (MA) and body temperature (BT). Mean level were increased for Cort and IMA, whereas no significant changes were o bserved for ACTH and BT Significantly higher plasma Cort morning value s were evidenced in BOX than sham-operated animals. In addition, compa red with the single prominent power spectrum for the 24 hours period o f control rats, the BOX animals displayed substantially lower 24 hours spectral power for the MA and BT circadian rhythms. These alterations suggest that olfactory bulbectomy, by disruption of the differences a nd efferences, induced drastic changes in the function of the endogeno us clock or of its regulating systems. From this point of view, bulbec tomized rats may therefore be a valuable model to studying the etiolog y of psychiatric disorders with rhythm disturbance.