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BioMed Research International
Volume 2014, Article ID 424982, 15 pages
http://dx.doi.org/10.1155/2014/424982
Research Article

Circadian Modulation of the Cl Equilibrium Potential in the Rat Suprachiasmatic Nuclei

1División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Apartado Postal 70-253, 04510 México, DF, Mexico
2Department of Psychology, Neuroscience & Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1
3McMaster Brain-Body Institute, St Joseph’s Healthcare, Hamilton, ON, Canada L8N 4A6

Received 27 January 2014; Revised 23 March 2014; Accepted 27 March 2014; Published 18 May 2014

Academic Editor: Mario Guido

Copyright © 2014 Javier Alamilla et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The suprachiasmatic nuclei (SCN) constitute a circadian clock in mammals, where -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 (EGABA) 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 EGABA close to −30 mV while in the ventral SCN they have an EGABA close to −60 mV; this difference reverses during the night, in the dorsal SCN neurons have an EGABA of −60 mV and in the ventral SCN they have an EGABA 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 EGABA in the SCN.