Serotoninergic control of the activity and expression of glial GABA transporters in the rat cerebellum.
Gamma-Aminobutyric acid (GABA) transporters (GAT-1, GAT-2, and GAT-3) play a key role in the termination of GABA transmission and the regulation of extracellular GABA concentrations. In the present study, pharmacological, cellular, and molecular analyses provide evidence for a modulatory effect of serotoninergic neurons on the activity and expression of glial GABA transporters in the rat cerebellum. Degeneration of serotoninergic neurons after in vivo 5,7-dihydroxytryptamine (5,7-DHT) treatment resulted in a significant decrease (-27%) in [3H]-GABA uptake into cerebellar punches. This decrease probably occurred via inhibition of GAT-2 or GAT-3 activity since their inhibitor, beta-alanine, induced a decrease in [3H]-GABA uptake in punches of sham-operated rats (-28%), but not in punches of 5,7-DHT-treated rats, demonstrating that serotonin terminal degeneration had already impaired the beta-alanine-sensitive component of GABA uptake. In contrast, nipecotic acid, a preferential inhibitor of GAT-1, induced comparable decreases in [3H]-GABA uptake comparable in punches of 5,7-DHT (-38%) versus sham-operated rats (-37%). The decreases in GAT-1 (-16%), GAT-2 (-34%), and GAT-3 (-32%) mRNA levels after 5,7-DHT treatment (detected by quantitative RT-PCR) are consistent with a serotoninergic control of GABA transporter expression at the transcriptional level. The cellular distribution of GAT-2 and GAT-3 mRNA, shown by in situ hybridization, suggests a glial localization of these transporters in the cerebellum and demonstrated a preferential anatomical localization of GAT-2 mRNA in the granular layer and of GAT-3 mRNA in the deep cerebellar nuclei. A direct serotoninergic control of glial GABA uptake was further demonstrated in vitro since serotonin stimulated the activity and mRNA expression of the GABA transporters in cerebellar astrocyte cultures.
Voutsinos
B
B
INSERM U433, Neurobiologie Expérimentale et Physiopathologie, Faculté de Médecine Laënnec, Lyon, France.
Dutuit
M
M
Reboul
A
A
Fevre-Montange
M
M
Bernard
A
A
Trouillas
P
P
Akaoka
H
H
Belin
M F
MF
Didier-Bazès
M
M
D015116:5,7-Dihydroxytryptamine / Q000633:toxicity*; D000818:Animals; D000831:Animals, Newborn; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis / Q000378:metabolism*; D002531:Cerebellum / Q000378:metabolism* / Q000473:pathology; D017931:DNA Primers; D005260:Female; D050485:GABA Plasma Membrane Transport Proteins; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009410:Nerve Degeneration; D009419:Nerve Tissue Proteins; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D009498:Neurotoxins / Q000633:toxicity; D015345:Oligonucleotide Probes; D027361:Organic Anion Transporters; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D050486:Serotonin Plasma Membrane Transport Proteins; D014158:Transcription, Genetic / Q000187:drug effects; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D002352:Carrier Proteins; D017931:DNA Primers; D050485:GABA Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D015345:Oligonucleotide Probes; D027361:Organic Anion Transporters; D012333:RNA, Messenger; D050486:Serotonin Plasma Membrane Transport Proteins; C493415:Slc6a1 protein, rat; C092004:Slc6a13 protein, rat; C493232:Slc6a4 protein, rat; D015116:5,7-Dihydroxytryptamine; D005680:gamma-Aminobutyric Acid