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. 2015 Sep 23;87(6):1290–1303. doi: 10.1016/j.neuron.2015.08.024

Figure 3.

Figure 3

Activation of Hippocampal Inputs Provides FFI of BA PNs

(A) Ex vivo cell-attached recording from a representative PN in response to single light pulses (20 superimposed sweeps, top; singularly represented in raster plot, bottom). Red circles denote spike negative peak.

(B) Mean probability of firing of PNs (bins = 10 ms, black: mean, red: SEM; n = 24).

(C) Whole-cell recording of the same cell as in (A) showing that the light pulse induced a PSP composed of an EPSP followed by a biphasic IPSP. On average, the peak amplitudes of the EPSP, early IPSP, and late IPSP were 8.9 ± 1 mV, 4.1 ± 0.8 mV, and 2.7 ± 0.6 mV (n = 24), respectively. Inset: Response to hyperpolarizing and depolarizing current injections showing stereotypic PN firing.

(D) Cell-attached recording from a representative IN in response to a single light pulse (20 superimposed sweeps, top; singularly represented in raster plot, bottom). Blue circles denote spike negative peak.

(E) Mean probability of firing of INs (bin = 10 ms, black: mean, red: SEM; n = 11).

(F) Whole-cell recording of the same cell as in (D) showing that the light stimulation evoked a monophasic EPSP. On average, the peak amplitude of the EPSP was 8.1 ± 0.7 mV (n = 24). Inset: Response to hyperpolarizing and depolarizing current injections displaying stereotypic IN firing.

(G) Minimum light power density (mW/mm2) necessary to trigger one spike in PNs (n = 33) and INs (n = 11). Significantly higher power was necessary to reach spike threshold in PNs (∗∗∗∗p < 0.0001).

(H) The IPSP induced by a single light pulse was blocked by glutamatergic antagonists NBQX (10 μm)/APV (100 μm), suggesting it was mediated by FFI due to activation of BA INs (n = 5).

(I) The early IPSP was blocked by the GABAA receptor antagonist SR95531 (10 μm, n = 5).

(J) The late IPSP was blocked by the GABAB receptor antagonist CGP54626 (5 μm, n = 26). Co-application of SR95531 and CGP54626 abolished IPSPs and increased the duration of the EPSP. All data from whole-cell recordings shown are three superimposed (gray) and average traces (black). Data are presented as means ± SEM.