Ah. Cai et Pm. Wise, AGE-RELATED-CHANGES IN LIGHT-INDUCED JUN-B AND JUN-D EXPRESSION - EFFECTS OF TRANSPLANTATION OF FETAL TISSUE CONTAINING THE SUPRACHIASMATICNUCLEUS, Journal of biological rhythms, 11(4), 1996, pp. 284-290
Fos and Jun mRNA and peptide exhibit a daily light-induced rhythm in t
he suprachiasmatic nucleus (SCN). The authors previously have reported
that Fos expression in the SCN is elevated prematurely during the dar
k, Light-induced Fos expression is attenuated in middle-aged rats, and
transplantation of fetal SCN tissue into the third ventricle of rats
of this age restores the daily pattern of Fos expression to that of th
e young. Using immunocytochemistry, the authors performed the present
study to determine whether Jun-B and Jun-D expression in the SCN is al
tered at the same stage during aging and, if so, whether transplantati
on of fetal tissue containing the SCN can restore the Light-induced rh
ythms of these two immediate early genes. All groups of rats were tran
scardially perfused 90 min prior to and after light onset. In young ra
ts, Light induced a robust increase in the number of Jun-B positive ce
lls in the SCN, whereas very few cells were labeled before light onset
. In middle-aged rats, the light-induced increase in the number of Jun
-B positive cells was significantly attenuated. Transplantation of fet
al SCN tissue into the middle-aged rats successfully restored light-in
duced Jun-B expression to the levels of young rats. By contrast, Jun-D
exhibited a constitutively high level of expression in the SCN both b
efore and after light onset, and light induced only a slight but signi
ficant increase. No age-related changes were detected in the expressio
n of Jun-D either before or after Light onset. Transplantation of feta
l SCN tissue did not alter the daily pattern of Jun-D expression in th
e middle-aged rats. These data suggest that (1) Light-induced activati
on of SCN neural activity is blunted during aging, (2) fetal SCN tissu
e can provide the critical support to allow the host to respond proper
ly to light cues, and (3) the age-related change in Jun-B expression i
n the middle-aged host SCN can be rescued by fetal SCN transplants.