期刊
JOURNAL OF COMPARATIVE NEUROLOGY
卷 442, 期 1, 页码 48-62出版社
WILEY-LISS
DOI: 10.1002/cne.1421
关键词
circadian; retrograde tracing; cholera toxin subunit B; vasopressin; gastrin releasing peptide; vasoactive intestinal peptide
The suprachiasmatic nuclei (SCN) contain a master clock driving the majority of circadian rhythms in mammals. It is believed that the SCN confers circadian rhythmicity as well as light responsiveness to pineal melatonin secretion via a direct projection to the paraventricular nucleus of the hypothalamus (PVN). Neurons in the SCN respond to light during subjective night with an expression of the immediate early gene c-fos. The number and distribution of c-Fos protein-containing neurons depend on the zeitgeber time (ZT) at which the light stimulus is presented. To investigate whether this phase-dependent activity is present in the SCN output neurons targeting the PVN, we combined retrograde cholera toxin subunit B (ChB) tracing from the PVN with c-Fos immunohistochemistry. Male golden hamsters were injected iontophoretically with ChB into the PVN area and 7 days later given a 1.5-hr light stimulus at either ZT 14 or ZT 19 followed by vascular fixation. Light stimulation at ZT 19 gave rise to more c-Fos containing neurons in the SCN than light presented at ZT 14. Double immunostaining for ChB and c-Fos revealed that light stimulation at ZT 14 induced c-Fos expression in 26.6% +/- 2.8% of the retrogradely filled perikarya, whereas light-stimulation at ZT 19 increased this fraction to 40.7% +/- 1.9%. This demonstrates the presence of a phase-dependent c-Fos induction in the suprachiasmatic-paraventricular projection system. Triple immunohistochemistry showed that light-activated output neurons contained both gastrin-releasing peptide and vasoactive intestinal. peptide and to a lesser extent vasopressin. The present findings prm, ide functional evidence poly of light activation of central pathways involved in the regulation of circadian output rhythms. (C) 2002 Wiley-Liss, Inc.
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