[The reciprocal relationships between the epiphysis and the suprachiasmatic nuclei of the hypothalamus during the restructuring of the circadian mobility in rats under an altered light regimen].

Pinealectomy and reserpine advanced the reorganization of the circadian rhythm of motor activity of rats following a ten-hour shift in the photoperiod. Bilateral electrolytic lesion of the hypothalamic suprachiasmatic nuclei and administration of the antidepressant drug, imipramine, on the contrary, delayed the rhythm change. The results suggest a possible antagonistic reciprocal relationship between the pineal gland and the main pacemaker, whose balance causes a gradual adaptation of animals to the changing environment. Fast reorganization of motor activity at pineal dysfunction or under the influence of depressogenic drugs could cause desynchronization and psychiatric disorders in a form of depression.