Choi, Hee Joo Lee, C. Justin Schroeder, Analyne Kim, Yoon Sik Jung, Seung Hoon Kim, Jeong Sook Kim, Do Young Son, Eun Ju Han, Hee Chul Hong, Seung Kil Colwell, Christopher S. Kim, Yang In 2024-01-20T23:05:35Z 2024-01-20T23:05:35Z 2021-09-03 2008-05-21 0270-6474 https://pubs.kist.re.kr/handle/201004/133484 Neurons in the suprachiasmatic nucleus (SCN) are responsible for the generation of circadian oscillations, and understanding how these neurons communicate to form a functional circuit is a critical issue. The neurotransmitter GABA and its receptors are widely expressed in the SCN where they mediate cell-to-cell communication. Previous studies have raised the possibility that GABA can function as an excitatory transmitter in adult SCN neurons during the day, but this work is controversial. In the present study, we first tested the hypothesis that GABA can evoke excitatory responses during certain phases of the daily cycle by broadly sampling how SCN neurons respond to GABA using extracellular single-unit recording and gramicidin-perforated-patch recording techniques. We found that, although GABA inhibits most SCN neurons, some level of GABA-mediated excitation was present in both dorsal and ventral regions of the SCN, regardless of the time of day. These GABA-evoked excitatory responses were most common during the night in the dorsal SCN region. The Na+-K+-2Cl(-) cotransporter (NKCC) inhibitor, bumetanide, prevented these excitatory responses. In individual neurons, the application of bumetanide was sufficient to change GABA-evoked excitation to inhibition. Calcium-imaging experiments also indicated that GABA-elicited calcium transients in SCN cells are highly dependent on the NKCC isoform 1 (NKCC1). Finally, Western blot analysis indicated that NKCC1 expression in the dorsal SCN is higher in the night. Together, this work indicates that GABA can play an excitatory role in communication between adult SCN neurons and that this excitation is critically dependent on NKCC1. English SOC NEUROSCIENCE CIRCADIAN CLOCK NA-K-2CL COTRANSPORTER DIFFERENTIAL EXPRESSION IN-VITRO RAT NEURONS PHASE RHYTHMS CHLORIDE SYSTEM Excitatory actions of GABA in the suprachiasmatic nucleus Article 10.1523/JNEUROSCI.5750-07.2008 1 JOURNAL OF NEUROSCIENCE, v.28, no.21, pp.5450 - 5459 JOURNAL OF NEUROSCIENCE 28 21 5450 5459 scie scopus 000256066200006 2-s2.0-45849127243 Neurosciences Neurosciences & Neurology Article CIRCADIAN CLOCK NA-K-2CL COTRANSPORTER DIFFERENTIAL EXPRESSION IN-VITRO RAT NEURONS PHASE RHYTHMS CHLORIDE SYSTEM circadian rhythm GABA mouse NKCC1 rat suprachiasmatic nucleus