Pitx3ak mice lack a functioning retina and nearly all dopamine neurons of the substantia nigra (SN). del Rio-Marten et al (2019) reported that entrainment of circadian rhythms to daily light-dark and feeding schedules is absent in these mice. With food limited to 12h/day, food anticipatory circadian rhythms failed to emerge, and metabolic rhythms failed to synchronize with locomotor and feeding rhythms. The authors propose that retinal innervation of the suprachiasmatic nucleus clock is required for development of cyclic metabolic homeostasis, but methodological issues limit interpretation of the results. Using standardized feeding schedules and procedures for distinguishing free-running from entrained circadian rhythms, we confirm that behavioral and metabolic rhythms in Pitx3ak mice do not entrain to LD cycles, but we find no desynchrony between these rhythms nor a deficit in entrainment to daily feeding schedules. SN dopamine neurons surviving in Pitx3ak mice may define a mininum population sufficient for food entrainment.

中文翻译：

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Pitx3亚型的小鼠定义了最小的多巴胺神经元群体，足以将行为和新陈代谢带入预定的进食

Pitx3ak小鼠缺乏正常运作的视网膜，几乎没有黑质（SN）的所有多巴胺神经元。del Rio-Marten等人（2019）报告说，这些小鼠中缺乏昼夜节律的昼夜节律和进食时间表。由于每天的食物限制为12小时，因此无法出现预期的食物昼夜节律，并且代谢节律也无法与运动和进食节律同步。作者提出，视交叉上核时钟的视网膜神经支配是循环代谢稳态的发展所必需的，但方法学问题限制了对结果的解释。使用标准化的喂食时间表和程序来区分自由奔跑的昼夜节律和夹杂的昼夜节律，我们确认Pitx3ak小鼠的行为节律和代谢节律不参与LD周期，但是我们发现这些节律之间没有失调，也没有每天进食时间表的不足。在Pitx3ak小鼠中存活的SN多巴胺神经元可能定义了足以诱捕食物的最小种群。