TY - JOUR
T1 - A novel GABA-mediated corticotropin-releasing hormone secretory mechanism in the median eminence
AU - Kakizawa, Keisuke
AU - Watanabe, Miho
AU - Mutoh, Hiroki
AU - Okawa, Yuta
AU - Yamashita, Miho
AU - Yanagawa, Yuchio
AU - Itoi, Keiichi
AU - Suda, Takafumi
AU - Oki, Yutaka
AU - Fukuda, Atsuo
N1 - Funding Information:
We are grateful to M. Watanabe (Hokkaido University School of Medicine) for the gift of the anti-NKCC1 antibody. This work was supported by Grants-in-Aid for Scientific Research on Innovative Areas (nos. 26110705 and 15H05872) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (to A.F.); Grants-in-Aid for Scientific Research (B) (no. 25293052) and for Challenging Exploratory Research (no. 26670512) from the Japan Society for the Promotion of Science (to A.F.); and a grant for a Practical Research Project for Rare/Intractable Diseases (no. 27280301) from the Japan Agency for Medical Research and Development.
Publisher Copyright:
2016 © The Authors.
PY - 2016/8
Y1 - 2016/8
N2 - Corticotropin-releasing hormone (CRH), which is synthesized in the paraventricular nucleus (PVN) of the hypothalamus, plays an important role in the endocrine stress response. The excitability of CRH neurons is regulated by g-aminobutyric acid (GABA)–containing neurons projecting to the PVN. We investigated the role of GABA in the regulation of CRH release. The release of CRH was impaired, accumulating in the cell bodies of CRH neurons in heterozygous GAD67-GFP (green fluorescent protein) knock-in mice (GAD67+/GFP), which exhibited decreased GABA content. The GABAA receptor (GABAAR) and the Na+-K+-2Cl− cotransporter (NKCC1), but not the K+-Cl− cotransporter (KCC2), were expressed in the terminals of the CRH neurons at the median eminence (ME). In contrast, CRH neuronal somata were enriched with KCC2 but not with NKCC1. Thus, intracellular Cl− concentrations ([Cl−]i) may be increased at the terminals of CRH neurons compared with concentrations in the cell body. Moreover, GABAergic terminals projecting from the arcuate nucleus were present in close proximity to CRH-positive nerve terminals. Furthermore, a GABAAR agonist increased the intracellular calcium (Ca2+) levels in the CRH neuron terminals but decreased the Ca2+ levels in their somata. In addition, the increases in Ca2+ concentrations were prevented by an NKCC1 inhibitor. We propose a novel mechanism by which the excitatory action of GABA maintains a steady-state CRH release from axon terminals in the ME.
AB - Corticotropin-releasing hormone (CRH), which is synthesized in the paraventricular nucleus (PVN) of the hypothalamus, plays an important role in the endocrine stress response. The excitability of CRH neurons is regulated by g-aminobutyric acid (GABA)–containing neurons projecting to the PVN. We investigated the role of GABA in the regulation of CRH release. The release of CRH was impaired, accumulating in the cell bodies of CRH neurons in heterozygous GAD67-GFP (green fluorescent protein) knock-in mice (GAD67+/GFP), which exhibited decreased GABA content. The GABAA receptor (GABAAR) and the Na+-K+-2Cl− cotransporter (NKCC1), but not the K+-Cl− cotransporter (KCC2), were expressed in the terminals of the CRH neurons at the median eminence (ME). In contrast, CRH neuronal somata were enriched with KCC2 but not with NKCC1. Thus, intracellular Cl− concentrations ([Cl−]i) may be increased at the terminals of CRH neurons compared with concentrations in the cell body. Moreover, GABAergic terminals projecting from the arcuate nucleus were present in close proximity to CRH-positive nerve terminals. Furthermore, a GABAAR agonist increased the intracellular calcium (Ca2+) levels in the CRH neuron terminals but decreased the Ca2+ levels in their somata. In addition, the increases in Ca2+ concentrations were prevented by an NKCC1 inhibitor. We propose a novel mechanism by which the excitatory action of GABA maintains a steady-state CRH release from axon terminals in the ME.
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U2 - 10.1126/sciadv.1501723
DO - 10.1126/sciadv.1501723
M3 - Article
C2 - 27540587
AN - SCOPUS:85016071986
VL - 2
JO - Science advances
JF - Science advances
SN - 2375-2548
IS - 8
M1 - e1501723
ER -