Alamilla Javier, Perez-Burgos Azucena, Quinto Daniel, Aguilar-Roblero Raúl
División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-253, 04510 México, DF, Mexico ; Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1.
División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-253, 04510 México, DF, Mexico ; McMaster Brain-Body Institute, St Joseph's Healthcare, Hamilton, ON, Canada L8N 4A6.
Biomed Res Int. 2014;2014:424982. doi: 10.1155/2014/424982. Epub 2014 May 18.
The suprachiasmatic nuclei (SCN) constitute a circadian clock in mammals, where γ-amino-butyric acid (GABA) neurotransmission prevails and participates in different aspects of circadian regulation. Evidence suggests that GABA has an excitatory function in the SCN in addition to its typical inhibitory role. To examine this possibility further, we determined the equilibrium potential of GABAergic postsynaptic currents (E(GABA)) at different times of the day and in different regions of the SCN, using either perforated or whole cell patch clamp. Our results indicate that during the day most neurons in the dorsal SCN have an E(GABA) close to -30 mV while in the ventral SCN they have an E(GABA) close to -60 mV; this difference reverses during the night, in the dorsal SCN neurons have an E(GABA) of -60 mV and in the ventral SCN they have an E(GABA) of -30 mV. The depolarized equilibrium potential can be attributed to the activity of the Na(+)-K(+)-2Cl(-) (NKCC) cotransporter since the equilibrium potential becomes more negative following addition of the NKCC blocker bumetanide. Our results suggest an excitatory role for GABA in the SCN and further indicate both time (day versus night) and regional (dorsal versus ventral) modulation of E(GABA) in the SCN.
视交叉上核（SCN）构成哺乳动物的昼夜节律时钟，其中γ-氨基丁酸（GABA）神经传递占主导地位，并参与昼夜节律调节的不同方面。有证据表明，GABA除了具有典型的抑制作用外，在SCN中还具有兴奋功能。为了进一步研究这种可能性，我们使用穿孔或全细胞膜片钳技术，测定了一天中不同时间以及SCN不同区域的GABA能突触后电流（E(GABA)）的平衡电位。我们的结果表明，白天背侧SCN中的大多数神经元的E(GABA)接近-30 mV，而腹侧SCN中的神经元的E(GABA)接近-60 mV；这种差异在夜间会逆转，背侧SCN神经元的E(GABA)为-60 mV，腹侧SCN神经元的E(GABA)为-30 mV。去极化的平衡电位可归因于Na(+)-K(+)-2Cl(-)（NKCC）共转运体的活性，因为加入NKCC阻滞剂布美他尼后平衡电位变得更负。我们的结果表明GABA在SCN中具有兴奋作用，并进一步表明SCN中E(GABA)存在时间（白天与夜晚）和区域（背侧与腹侧）调制。
