AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 6 1186-R1192, Copyright © 1993 by American Physiological Society
Suprachiasmatic nucleus lesion increases corticosterone secretion
R. M. Buijs, A. Kalsbeek, T. P. van der Woude, J. J. van Heerikhuize and S. Shinn
Neurosciences Loeb Medical Research Institute, Ottawa Civic Hospital, Ontario, Canada.
The diurnal rhythm of corticosteroid secretion is controlled by the
suprachiasmatic nucleus (SCN). In rats, plasma corticosteroid levels rise
just before the onset of the activity period during the dark phase. Our
previous results indicated that vasopressin as a neurotransmitter from the
SCN inhibited corticosteroid secretion in the area of the
paraventricular/dorsomedial nucleus of the hypothalamus. We hypothesized
that during the day the SCN may serve as an inhibitory system for
corticosteroid secretion. To investigate this possibility, intact and
SCN-lesioned animals were exposed to mild stress in the morning and evening
and their plasma corticosteroid levels were monitored. The results indicate
that SCN-lesioned animals have higher morning corticosteroid levels and
respond both in the morning and evening with higher corticosteroid levels
after stress than do intact control animals. We conclude, therefore, that
these results indicate an inhibitory role of the SCN on corticosteroid
secretion. The apparent discrepancy with the reported stimulatory role of
the SCN on adrenocorticotropic hormone secretion is discussed.
