TY - JOUR
T1 - Localization and expression of GABA transporters in the suprachiasmatic nucleus
AU - Moldavan, Michael
AU - Cravetchi, Olga
AU - Williams, Melissa
AU - Irwin, Robert P.
AU - Aicher, Sue A.
AU - Allen, Charles N.
N1 - Funding Information:
The work was supported by National Institutes of Health (NIH) grants R01 NS036607 to C.N.A. and P30 NS061800 to S.A.A. We thank Drs Karin Mullendorff and Linda Ruggiero for advice on Western blotting and immunohistochemistry techniques, and Sam Hermes for immunogold tissue processing. We thank Dr Michael Hughes for helpful advice in analysing our data with JTK_Cycle. For technical assistance, we acknowledge Dr Stefanie Kaech Petrie and Aurelie Snyder, of the Advanced Light Microscopy Core (ALM), which is supported by shared instrumentation grants S10 RR023432 and S10 RR025440 from the National Center for Research Resources (NIH). The electron microscope was purchased through an instrumentation grant from Murdock Charitable Trust (TEM).
Publisher Copyright:
© 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - GABA is a principal neurotransmitter in the suprachiasmatic hypothalamic nucleus (SCN), the master circadian clock. Despite the importance of GABA and GABA uptake for functioning of the circadian pacemaker, the localization and expression of GABA transporters (GATs) in the SCN has not been investigated. The present studies used Western blot analysis, immunohistochemistry and electron microscopy to demonstrate the presence of GABA transporter 1 (GAT1) and GAT3 in the SCN. By using light microscopy, GAT1 and GAT3 were co-localized throughout the SCN, but were not expressed in the perikarya of arginine vasopressin- or vasoactive intestinal peptide-immunoreactive (-ir) neurons of adult rats, nor in the neuronal processes labelled with the neurofilament heavy chain. Using electron microscopy, GAT1- and GAT3-ir was found in glial processes surrounding unlabelled neuronal perikarya, axons, dendrites, and enveloped symmetric and asymmetric axo-dendritic synapses. Glial fibrillary acidic protein-ir astrocytes grown in cell culture were immunopositive for GAT1 and GAT3 and both GATs could be observed in the same glial cell. These data demonstrate that synapses in the SCN function as 'tripartite' synapses consisting of presynaptic axon terminals, postsynaptic membranes and astrocytes that contain GABA transporters. This model suggests that astrocytes expressing both GATs may regulate the extracellular GABA, and thereby modulate the activity of neuronal networks in the SCN. GABA transporters (GAT) are an important component of GABAergic neurotransmission in the suprachiasmatic nucleus (SCN), the master circadian clock. GAT1 and GAT3 were co-localized throughout the SCN but not in the perikarya of vasopressin or vasoactive intestinal peptide neurons. By electron microscopy, GAT1 and GAT3 were found in glial processes surrounding unlabeled neurons, axons, dendrites, and enveloped axodendritic synapses. GABAergic synapses in the SCN function as 'tripartite' synapses consisting of presynaptic axon terminals, postsynaptic GABA(A) receptors, and glial cells that contain GABA transporters. This model suggests that glial cells modulate SCN neuronal network activity by regulating the extracellular GABA concentration.
AB - GABA is a principal neurotransmitter in the suprachiasmatic hypothalamic nucleus (SCN), the master circadian clock. Despite the importance of GABA and GABA uptake for functioning of the circadian pacemaker, the localization and expression of GABA transporters (GATs) in the SCN has not been investigated. The present studies used Western blot analysis, immunohistochemistry and electron microscopy to demonstrate the presence of GABA transporter 1 (GAT1) and GAT3 in the SCN. By using light microscopy, GAT1 and GAT3 were co-localized throughout the SCN, but were not expressed in the perikarya of arginine vasopressin- or vasoactive intestinal peptide-immunoreactive (-ir) neurons of adult rats, nor in the neuronal processes labelled with the neurofilament heavy chain. Using electron microscopy, GAT1- and GAT3-ir was found in glial processes surrounding unlabelled neuronal perikarya, axons, dendrites, and enveloped symmetric and asymmetric axo-dendritic synapses. Glial fibrillary acidic protein-ir astrocytes grown in cell culture were immunopositive for GAT1 and GAT3 and both GATs could be observed in the same glial cell. These data demonstrate that synapses in the SCN function as 'tripartite' synapses consisting of presynaptic axon terminals, postsynaptic membranes and astrocytes that contain GABA transporters. This model suggests that astrocytes expressing both GATs may regulate the extracellular GABA, and thereby modulate the activity of neuronal networks in the SCN. GABA transporters (GAT) are an important component of GABAergic neurotransmission in the suprachiasmatic nucleus (SCN), the master circadian clock. GAT1 and GAT3 were co-localized throughout the SCN but not in the perikarya of vasopressin or vasoactive intestinal peptide neurons. By electron microscopy, GAT1 and GAT3 were found in glial processes surrounding unlabeled neurons, axons, dendrites, and enveloped axodendritic synapses. GABAergic synapses in the SCN function as 'tripartite' synapses consisting of presynaptic axon terminals, postsynaptic GABA(A) receptors, and glial cells that contain GABA transporters. This model suggests that glial cells modulate SCN neuronal network activity by regulating the extracellular GABA concentration.
KW - Circadian rhythm
KW - Electron microscopic imaging
KW - Hypothalamus
KW - Immunohistochemistry
KW - Suprachiasmatic nucleus
KW - Western blot
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U2 - 10.1111/ejn.13083
DO - 10.1111/ejn.13083
M3 - Article
C2 - 26390912
AN - SCOPUS:84955171330
SN - 0953-816X
VL - 42
SP - 3018
EP - 3032
JO - European Journal of Neuroscience
JF - European Journal of Neuroscience
IS - 12
ER -