Centro Universitario de Investigaciones Biomédicas, Universidad de Colima, Colima, Mexico.
División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad de Mexico, Mexico.
J Neurosci Res. 2024 Aug;102(8):e25373. doi: 10.1002/jnr.25373.
The master control of mammalian circadian rhythms is the suprachiasmatic nucleus (SCN), which is formed by the ventral and dorsal regions. In SCN neurons, GABA has an important function and even excitatory actions in adulthood. However, the physiological role of this neurotransmitter in the developing SCN is unknown. Here, we recorded GABAergic postsynaptic currents (in the perforated-patch configuration using gramicidin) to determine the chloride reversal potential (E) and also assessed the immunological expression of the Na-K-Cl cotransporter 1 (NKCC1) at early ages of the rat (postnatal days (P) 3 to 25), during the day and night, in the two SCN regions. We detected that E greatly varied with age and depending on the SCN region and time of day. Broadly speaking, E was more hyperpolarized with age, except for the oldest age studied (P20-25) in both day and night in the ventral SCN, where it was less negative. Likewise, E was more hyperpolarized in the dorsal SCN both during the day and at night; while E was more negative at night both in the ventral and the dorsal SCN. Moreover, the total NKCC1 fluorescent expression was higher during the day than at night. These results imply that NKCC1 regulates the circadian and developmental fluctuations in the [Cl] to fine-tune E, which is crucial for either excitatory or inhibitory GABAergic actions to occur in the SCN.
哺乳动物昼夜节律的主控中心是视交叉上核（SCN），它由腹侧和背侧两部分组成。在 SCN 神经元中，GABA 在成年期具有重要作用，甚至具有兴奋作用。然而，这种神经递质在发育中的 SCN 中的生理作用尚不清楚。在这里，我们记录了 GABA 能突触后电流（在穿孔贴片配置中使用短杆菌肽），以确定氯离子反转电位（E），并评估了大鼠早期（出生后第 3 天至第 25 天）、白天和黑夜两个 SCN 区域中 Na-K-Cl 共转运蛋白 1（NKCC1）的免疫表达。我们发现 E 随年龄的变化而变化，并且取决于 SCN 区域和一天中的时间。总的来说，E 随年龄的增长而更加超极化，除了在白天和黑夜的腹侧 SCN 中研究的最年长年龄（P20-25）外，在那里它的负值较小。同样，白天和黑夜背侧 SCN 中的 E 更加超极化；而白天和黑夜的腹侧和背侧 SCN 中 E 的负值更大。此外，白天 NKCC1 的总荧光表达高于夜间。这些结果表明，NKCC1 调节[Cl]的昼夜和发育波动，以微调 E，这对于 SCN 中 GABA 能兴奋或抑制作用的发生至关重要。
