Figure 5.
Synaptic Dynamics Evoked by TBS in BA PNs and INs
(A) Synaptic potentials (three superimposed sweeps, gray traces; average, black trace) evoked by TBS in representative PNs and in a representative IN in control and in presence of the GABAA (SR95531, 10 μM) and GABAB receptor (CGP54626, 5 μM) antagonists.
(B and C) Left, peak of EPSP and membrane potential recorded from PNs for each TBS train in control (n = 34) and in the presence of CGP54626 (n = 17). Right, membrane potential and EPSP peak compared between the first, second, and tenth trains of the TBS. Hyperpolarization and depression of the EPSP peak were blocked by CGP54626. In control, the membrane potential change from baseline was −3.7 ± 0.5 mV at the second train and −0.7 ± 0.5 mV at the tenth train. In the presence of CGP54626, these values were −0.2 ± 0.4 mV and +1.5 ± 0.7 mV. In control, the EPSP peak change from the first train was −2.6 ± 0.6 mV at the second train and +0.4 ± 0.5 mV at the tenth train. In the presence of CGP54626, these values were +0.2 ± 0.7 mV and +2.6 ± 0.8 mV.
(D) IPSP amplitude recorded from PNs for each TBS train in control (n = 34) and in presence of CGP54626 (n = 17). Note that the control IPSP that starts as hyperpolarizing (negative potential value) becomes depolarizing in response to the following stimuli during TBS (positive potential values). Right, IPSP amplitude is compared between the first, second, and tenth trains of the TBS. IPSP depression was blocked by CGP54626. In control, the IPSP amplitude change from the first train was +7.3 ± 0.8 mV at the second train and +5.3 ± 0.5 mV at the tenth train. In the presence of CGP54626, these values were +1.3 ± 0.6 mV and +1 ± 0.6 mV.
(E) EPSP area recorded from PNs for each TBS train in control (n = 30) and in the presence of CGP54626 (n = 15). Right, broadening of EPSP area with the second TBS train. Broadening still persisted at the tenth train and was blocked by CGP54626. In control, the EPSP area change from the first train was +3.2 ± 0.7 mV at the second train and +1.5 ± 0.4 mV at the tenth train, In the presence of CGP54626, these values were +0.2 ± 0.1 mV and +0.5 ± 0.3 mV.
(F) Left, EPSP amplitude for each train of the TBS in presence of SR95531 and CGP54626 in PNs (n = 6) and in INs (n = 23). Right, the EPSP amplitude was stable in PNs in presence of SR95531 and CGP54626. In INs, the EPSP amplitude significantly increased at the tenth TBS train. At the tenth train, EPSP amplitude was significantly more depolarized in INs than PNs. In control, the EPSP amplitude change from the first train was −0.6 ± 1 mV at the second train and +2.6 ± 1 mV at the tenth train. In the presence of CGP54626, these values were −0.3 ± 0.5 mV and +0.5 ± 0.8 mV. ∗p < 0.05; ∗∗p < 0.01; ∗∗∗p < 0.001; ∗∗∗∗p < 0.0001. Data are presented as means ± SEM.