[3H] gamma-aminobutyric acid transport in rat substantia nigra pars reticulata synaptosomes: pharmacological characterization and phorbol ester-induced inhibition.
In synaptosomes from rat substantia nigra pars reticulata, [3H] gamma-aminobutyric acid (GABA) uptake was inhibited by GABA, (+/-)-nipecotic acid, beta-alanine and SKF 89976-A. Inhibition was concentration-dependent and monophasic, with IC50 values that agree with those reported for the cloned rat GABA transporter GAT-1. [3H]GABA uptake was modestly, but significantly, reduced (21 +/- 3% inhibition) by 100 nM phorbol 12-tetradecanoyl-13-acetate (TPA), an activator of protein kinase C (PKC). The inhibitory action of TPA was reversed by the PKC inhibitor staurosporine (100 nM). Saturation analysis revealed that TPA reduced the maximum capacity of transport with no change in the affinity for GABA. [3H]GABA uptake was unaffected by either forskolin (10 microM) or 8-bromo-cAMP (500 microM). These results indicate that SNr GABAergic afferents express the GAT-1 transporter whose activity can be regulated by a PKC-mediated mechanism.
Bahena-Trujillo
R
R
Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados, Mexico, D.F, Mexico. jaarias@fisio.cinvestav.mx
Arias-Montaño
J A
JA
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001479:Basal Ganglia / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002273:Carcinogens / Q000494:pharmacology*; D005576:Colforsin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018682:GABA Agents / Q000494:pharmacology; D009557:Nipecotic Acids / Q000494:pharmacology; D011392:Proline / Q000031:analogs & derivatives*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D019311:Staurosporine / Q000494:pharmacology; D013378:Substantia Nigra / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000201:enzymology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014316:Tritium; D015091:beta-Alanine / Q000494:pharmacology; D005680:gamma-Aminobutyric Acid / Q000493:pharmacokinetics*
D002273:Carcinogens; D004791:Enzyme Inhibitors; D018682:GABA Agents; D009557:Nipecotic Acids; D014316:Tritium; D015091:beta-Alanine; D005576:Colforsin; C030278:nipecotic acid; D015124:8-Bromo Cyclic Adenosine Monophosphate; D005680:gamma-Aminobutyric Acid; C045598:N-(4,4-diphenyl-3-butenyl)nipecotic acid; D011392:Proline; C010983:homoproline; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate