Figure 6.

Optical Stimulation of vCA1 Axons with Firing Pattern of a vCA1 Pyramidal Cell Recapitulates Synaptic Dynamics Evoked by TBS

(A) Synaptic potentials evoked by optical stimulation of vCA1 axons with firing pattern of a BLA-projecting vCA1 pyramidal cell recorded during exploratory behavior.

(B) PNs membrane potential preceding each light pulse (n = 8).

(C) Membrane potential compared between first, second, and last light pulses. Hyperpolarization occurs at the second light pulse but is recovered by the last light pulse. Delta membrane potential (compared to membrane potential before the first light pulse) was −4.2 ± 0.8 mV (second light pulse) and +1.2 ± 1.9 mV (last light pulse).

(D) IPSP amplitude plotted for each light pulse (n = 8).

(E) IPSP amplitude compared between first, second, and last light pulses. IPSP depresses at the second light pulse and remains significantly reduced until the last light pulse. The change of the IPSP amplitude (compared to IPSP amplitude following first light pulse) was +9.1 ± 0.8 mV (second IPSP) and +8.3 ± 1.7 mV (last IPSP).

(F) Representative voltage-clamp trace from PN showing TBS-evoked EPSPs and IPSPs at the first and second TBS trains at different holding potentials (from −90 mV to −50 mV, 5-mV steps).

(G) IPSC amplitude plotted for each holding potential for first and second TBS trains (n = 6).

(H) The second TBS train causes both a significant decrease in GABA_A synaptic conductance (left) and a significant shift of the IPSC reversal potential (E_GABA) toward more depolarized membrane potentials (right). ^∗p < 0.05; ^∗∗p < 0.01; ^∗∗∗p < 0.001; ^∗∗∗∗p < 0.0001. Data are presented as means ± SEM.