Rapid antidepressants stimulate the decoupling of GABAB receptors from GIRK/Kir3 channels through increased protein stability of 14-3-3η

A single injection of N-methyl-D-aspartate receptor (NMDAR) antagonists produces a rapid antidepressant response. Lasting changes in the synapse structure and composition underlie the effectiveness of these drugs. We recently discovered that rapid antidepressants cause a shift in the gamma-aminobutyric acid receptor (GABA(B)R) signaling pathway, such that GABA(B)R activation shifts from opening inwardly rectifiying potassium channels (Kir/GIRK) to increasing resting dendritic calcium signal and mammalian Target of Rapamycin activity. However, little is known about the molecular and biochemical mechanisms that initiate this shift. Herein, we show that GABA(B)R signaling to Kir3 (GIRK) channels decreases with NMDAR blockade. Blocking NMDAR signaling stabilizes the adaptor protein 14-3-3 eta, which decouples GABA(B)R signaling from Kir3 and is required for the rapid antidepressant efficacy. Consistent with these results, we find that key proteins involved in GABA(B)R signaling bidirectionally change in a depression model and with rapid antidepressants. In socially defeated rodents, a model for depression, GABA(B)R and 14-3-3 eta levels decrease in the hippocampus. The NMDAR antagonists AP5 and Ro-25-6981, acting as rapid antidepressants, increase GABA(B)R and 14-3-3 eta expression and decrease Kir3.2. Taken together, these data suggest that the shift in GABA(B)R function requires a loss of GABA(B)R-Kir3 channel activity mediated by 14-3-3 eta. Our findings support a central role for 14-3-3 eta in the efficacy of rapid antidepressants and define a critical molecular mechanism for activity-dependent alterations in GABA(B)R signaling.