Control of Glutamate Clearance and Synaptic Efficacy by Glial Coverage of Neurons
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Hypothalamic coronal slices (300 μm) including the supraoptic nuclei were obtained as described (28) from virgin (1- to 2-month-old) lactating (8th day of lactation) and postlactating (at least 6 weeks after weaning) Wistar rats. After dissection slices were maintained at 30° to 34°C for at least 1 hour in a submerged chamber containing artificial cerebrospinal fluid (ACSF) equilibrated with 95% O 2 and 5% CO 2 and then transferred to a superfusing chamber. The ACSF contained (in mM) 123 NaCl 2.5 KCl 1 Na 2 HPO 4 26.2 NaHCO 3 1.3 MgCl 2 2.5 CaCl 2 and 10 glucose (pH 7.4; 295 mosmol kg −1 ). Whole-cell recording electrodes were filled with a solution containing (in mM) 120 K-gluconate 20 KCl 10 Hepes 1 EGTA 1.3 MgCl 2 0.1 CaCl 2 2 Mg-ATP 0.3 GTP and 0.1 leupeptin. All recordings were obtained in the presence of 10 μM bicuculline. Miniature EPSCs obtained in the presence of tetrodotoxin (0.5 μM) were stored on videotape and analyzed off-line. Data were compared statistically with the nonparametric Kolmogorov-Smirnov test or the paired Student's t test. Significance was assessed at P < 0.05. All data are reported as the mean ± SEM.
PPF is expressed as the amplitude ratio (S2/S1) of the second synaptic response (S2) over the first synaptic response (S1).
We thank D. T. Theodosis for helpful discussions and comments on the manuscript. Supported in part by grants from the Conseil Régional d'Aquitaine (970301209) and from the Association pour la Recherche Médicale en Aquitaine. R.P. is supported by the French Ministry of Education.