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. 2009 Sep 24;284(47):32544–32550. doi: 10.1074/jbc.M109.040071

FIGURE 5.

FIGURE 5.

Blockade of L-type VGCCs increases the turnover of GABAARs. A, hippocampal neurons (18–21 DIV) were treated with 10 μm nifedipine for 24 h, followed by a pulse chase with [35S]methionine. Neurons were lysed in 1% SDS and diluted in RIPA buffer, and GABAAR β3 subunits were immunoprecipitated with anti-β3 IgG antibodies or nonspecific IgG antibodies (as indicated) and subjected to SDS-PAGE. Band intensities were quantified by phosphorimage spectrometry, and data represent the mean ± S.E. percentage of levels at time 0. *, significantly different from 0 h (p < 0.05; t test; n = 3). B, inhibition of proteasome activity blocked the effects of nifedipine on GABAAR β3 expression. Hippocampal neurons (18–21 DIV) were treated with or without 10 μm nifedipine for 24 h, and 10 μm MG132 was added for the last 8 h of the nifedipine incubation as indicated. Neurons were lysed, and Western blots were probed with anti-β3 IgG antibodies. Data represent the mean ± S.E. percentage of control (Ctrl) values. *, significantly different (p < 0.05); **, significantly different (p < 0.01; one-way analysis of variance and Bonferroni post-test; n = 3).