title: Localization and expression of GABA transporters in the suprachiasmatic nucleus.
abstract: 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.
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Moldavan
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Cravetchi
authors.affiliation: Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA.
authors.forename: Melissa
authors.initials: M
authors.lastname: Williams
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Irwin
authors.affiliation: Physiology and Pharmacology, Oregon Health & Science University, Portland, OR, USA.
authors.forename: Sue A
authors.initials: SA
authors.lastname: Aicher
authors.affiliation: Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, 3181 S.W. Sam Jackson Park Road, Portland, OR, 97239-3098, USA.|Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, USA.
authors.forename: Charles N
authors.initials: CN
authors.lastname: Allen
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D001253:Astrocytes / Q000378:metabolism* / Q000648:ultrastructure; D015153:Blotting, Western; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000502:physiology; D050485:GABA Plasma Membrane Transport Proteins / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D017207:Rats, Sprague-Dawley; D013493:Suprachiasmatic Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
chemical_list: D050485:GABA Plasma Membrane Transport Proteins; D005904:Glial Fibrillary Acidic Protein; C493415:Slc6a1 protein, rat; C493417:Slc6a11 protein, rat; D001127:Arginine Vasopressin; D014660:Vasoactive Intestinal Peptide
keywords: Western blot; circadian rhythm; electron microscopic imaging; hypothalamus; immunohistochemistry; suprachiasmatic nucleus