Nature. Control sedative and circadian rhythms to coordinate changes in the retinal input loop.

The suprachiasmatic nucleus (SCN), as a key regulator of the central system, controls and coordinates the regulation of circadian rhythm.the system integrates a variety of time cues from sensory, circadian and metabolic systems to produce a unified perception of the environment.generally speaking, the biological clock of the central system is affected by light signals, while the biological clock of the peripheral system is affected by diet.however, little is known about how the brain integrates these time cues to drive the output of circadian rhythms.previous studies have shown that in mammals, light is transmitted through the retinal ganglion cell subpopulations (iprgcs) to the circadian rhythm center to drive the light rhythm assimilation (simply, the change of light intensity is almost consistent with that of the circadian rhythm).on April 22, 2020, the samer Hattar research team of the National Institute of mental health published an article in the journal Nature It was found that retinal ganglion cells could control not only the light rhythm assimilation, but also the diet rhythm assimilation process, which revealed the retinal input loop controlling the non optical guidance.the researchers used limited time to obtain food as the only time clue (a method of giving food at a specific time), and found that normal mice showed strong food anticipation activity, and mice showed lower food expected activity after early postpartum knockout of light sensitive retinal ganglion cells (iprgcs).but surprisingly, in adulthood, the knockout of iprgcs showed strong food anticipation activity.these results indicate that the nerves innervated by iprgc play a key role in the coordination of dietary rhythm in the early postpartum period, and there is an obvious time window effect.which brain region is involved in this? Previous studies have confirmed that the intergenic lobular (IGL) receives intensive neural input from iprgc and participates in the regulation of circadian rhythm by driving light signals and dietary signals.the number of IGL activated neurons in the above experimental scheme was significantly reduced, which indicated that the IGL brain region participated in the process of dietary rhythm assimilation. Neuropeptide Y neurons were mainly found in the brain area ofIGL.previous studies have proposed that neurons projecting from the dorsal raphe nucleus to IGL release neuropeptide Y, which activates SCN, and then plays a non optical guidance role.therefore, neuropeptide Y signal in the brain region of IGL may be involved in the process of dietary rhythm coordination regulated by iprgc.the researchers found that IGL projected neuropeptide Y neurons to SCN through virus tracing technology. The expression of neuropeptide Y in IGL and SCN was decreased after iprgc knockout in early postpartum, which indicated that iprgc could affect the expression of neuropeptide Y in igl-scn.it was further found that there was a disorder of dietary regulation assimilation in NPY knockout mice.these results point to that the neurons expressing neuropeptide Y in IGL play a key role in the process of dietary rhythm assimilation.subsequently, the researchers reduced the release of neuropeptide Y (NPY) in the brain region of IGL through the virus, and the mice showed a similar phenomenon to NPY knockout mice.in addition, inhibition of igl-scn neural circuit by photogenetics significantly reduced the expected food activity of mice, similar to the results of early knockout of iprgc.in general, we found that retinal ganglion cells, which regulate optical guidance, can also regulate diet related rhythmic synergism, specifically, retinal ganglion cells regulate the dietary related guidance by influencing the release of neuropeptide Y from IGL projections to SCN neurons.original link: