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Organization of the Human Circadian System

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Final rept. 1 Jun 1996-30 Nov 1998

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1. Neuron innervation of the SCN. The 5HT innervation of the monkey SCN was analysed in brains from 5 macaque monkeys using immunocytochemistry with an antiserum against 5HT. There is a dense innervation of the SCN core, the area characterized by receiving direct retinal input. The surrounding area is not innervated but the perbSCN area also has a dense 5HT innervation. In the human brain, this nnerration was analysed using an antiserum against the serotonin transporter. Like the monkey, the human SCN has a dense 5HT innervation over the core. These data indicate that the 5HT innervation of the SCN is stable across mammalian species. 2. Clk Gene Expression in the HumaSCN. The human elk gene was cloned by Takahashi and his colleaguesSteeves et al, 1999 and an analysis of its localization was performed in this laboratory using in situ hybridization histochemistry. Clk was expressed at high levels in the human SCN, much higher than in adjacent anterior hypothalamus. 3. Clk Gene Expression in the Human Hypothalamus. The expression of clk was low in most hypothalamic areas with the exception of the SCN, paraventricular nucleusPVH, and the supraopticSON nuclens. In comparing controls against Alzheimers disease AD, we found that clk expression was significantly higher in all areas in the AD brains. The interpretation of this finding is unclear. 4. Rhythmicity of clk Gene Expression in the SCN and Other Hypothalamic Areas. The expression of clk was constant in the SCN and other hypothalamic areas in both Ad and control brains over the 24 hour period.

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  • Biochemistry
  • Anatomy and Physiology

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