Transplantation of fetal suprachiasmatic nuclei into middle-aged
rats restores diurnal fos expression in the host.
Cai, Aihua, Michael N. Lehman, Jonathan M. Lloyd, Phyllis M. Wise.
Department of Physiology, School of Medicine, University of
Maryland at Baltimore, Baltimore, Maryland 21201; Department of
Anatomy and Cell Biology, College of Medicine, University of
Cincinnati, Cincinnati, OH 45267; Department of Anatomy, Health
Sciences Center, University of Oklahoma, Oklahoma City, Oklahoma
73190; Department of Physiology, College of Medicine, University of
Kentucky, Lexington, Kentucky 40536
APStracts 3:0292R, 1996.
In young animals, the suprachiasmatic nuclei (SCN) of the
hypothalamus, which are critical circadian pacemakers, exhibit a
light-induced diurnal rhythm in Fos expression. The expression of
this immediate early gene has been used as an index of the activity
of the SCN and their ability to respond to external cues which
entrain them, such as light. In the present study, we show that by
the time rats reach middle-age, baseline Fos expression increases
prematurely during the dark and that light-induced Fos expression is
blunted and delayed. We also demonstrate that transplantation of
fetal tissue containing the SCN into the third cerebral ventricle of
middle-aged rats enables aged hosts to regain the ability to exhibit
diurnal patterns of Fos expression that are strikingly similar to
that observed in young animals. Our findings lead to the following
conclusions: (1) the diurnal pattern of activity of SCN cells is
blunted in middle-aged rats; and (2) SCN transplants provide unique
signals that enable the cellular systems of the host to regain
rhythmic functional capabilities. These results provide new insights
into the critical active role that the host plays in restoration of
function evoked by the presence of a transplant.
Received 23 February 1996; accepted in final form 9 July 1996.
APS Manuscript Number R110-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 August 1996