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Suprachiasmatic nucleus
About: Suprachiasmatic nucleus is a research topic. Over the lifetime, 5611 publications have been published within this topic receiving 341005 citations.
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TL;DR: It is shown that melanopsin is present in cell bodies, dendrites, and proximal axonal segments of a subset of rat RGCs, most likely the visual pigment of phototransducing R GCs that set the circadian clock and initiate other non–image-forming visual functions.
Abstract: The primary circadian pacemaker, in the suprachiasmatic nucleus (SCN) of the mammalian brain, is photoentrained by light signals from the eyes through the retinohypothalamic tract. Retinal rod and cone cells are not required for photoentrainment. Recent evidence suggests that the entraining photoreceptors are retinal ganglion cells (RGCs) that project to the SCN. The visual pigment for this photoreceptor may be melanopsin, an opsin-like protein whose coding messenger RNA is found in a subset of mammalian RGCs. By cloning rat melanopsin and generating specific antibodies, we show that melanopsin is present in cell bodies, dendrites, and proximal axonal segments of a subset of rat RGCs. In mice heterozygous for tau-lacZ targeted to the melanopsin gene locus, beta-galactosidase-positive RGC axons projected to the SCN and other brain nuclei involved in circadian photoentrainment or the pupillary light reflex. Rat RGCs that exhibited intrinsic photosensitivity invariably expressed melanopsin. Hence, melanopsin is most likely the visual pigment of phototransducing RGCs that set the circadian clock and initiate other non-image-forming visual functions.
2,359 citations
TL;DR: Estimation of transcripts encoding selected hypothalamic peptides associated with energy balance was attenuated in the Clock mutant mice, suggesting that the circadian clock gene network plays an important role in mammalian energy balance.
Abstract: The CLOCK transcription factor is a key component of the molecular circadian clock within pacemaker neurons of the hypothalamic suprachiasmatic nucleus. We found that homozygous Clock mutant mice have a greatly attenuated diurnal feeding rhythm, are hyperphagic and obese, and develop a metabolic syndrome of hyperleptinemia, hyperlipidemia, hepatic steatosis, hyperglycemia, and hypoinsulinemia. Expression of transcripts encoding selected hypothalamic peptides associated with energy balance was attenuated in the Clock mutant mice. These results suggest that the circadian clock gene network plays an important role in mammalian energy balance.
2,241 citations
TL;DR: It is shown that temporal feeding restriction under light-dark or dark-dark conditions can change the phase of circadian gene expression in peripheral cell types by up to 12 h while leaving thephase of cyclic gene expressionIn the SCN unaffected.
Abstract: In mammals, circadian oscillators exist not only in the suprachiasmatic nucleus, which harbors the central pacemaker, but also in most peripheral tissues. It is believed that the SCN clock entrains the phase of peripheral clocks via chemical cues, such as rhythmically secreted hormones. Here we show that temporal feeding restriction under light–dark or dark–dark conditions can change the phase of circadian gene expression in peripheral cell types by up to 12 h while leaving the phase of cyclic gene expression in the SCN unaffected. Hence, changes in metabolism can lead to an uncoupling of peripheral oscillators from the central pacemaker. Sudden large changes in feeding time, similar to abrupt changes in the photoperiod, reset the phase of rhythmic gene expression gradually and are thus likely to act through a clock-dependent mechanism. Food-induced phase resetting proceeds faster in liver than in kidney, heart, or pancreas, but after 1 wk of daytime feeding, the phases of circadian gene expression are similar in all examined peripheral tissues.
2,083 citations
TL;DR: The purpose of the present study was to reinvestigate the role of the central retinal projections in neuroendocrine regulation and find that lesions in the suprachiasmatic region of the hypothalamus abolish the constant estrous response to light in the female rat.
2,062 citations
TL;DR: Bilateral electrolytic lesions in the suprachiasmatic nuclei permanently eliminated nocturnal and circadian rhythms in drinking behavior and locomotor activity of albino rats.
Abstract: Bilateral electrolytic lesions in the suprachiasmatic nuclei permanently eliminated nocturnal and circadian rhythms in drinking behavior and locomotor activity of albino rats. The generation of 24-hr behavioral rhythms and the entrainment of these rhythms to the light-dark cycle of environmental illumination may be coordinated by neurons in the suprachiasmatic region of the rat brain. Destruction of the medial preoptic area had no effect on 24-hr drinking rhythms.
1,990 citations