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. 2022 Feb 28;11:e71965. doi: 10.7554/eLife.71965

Figure 9. Basal forebrain (BF)-evoked GABAergic excitation in a fraction of type 2.1 periglomerular (PG) cells.

Figure 9.

(A) Example of a BF-evoked excitatory response in a PG cell. One representative loose cell-attached (LCA) recording episode (duration 2 s) is shown on top. Photostimulation of the BF fibers (blue arrow) induced an inward current followed by a single spike (inset). Each tick is a spike in the raster plot of these cell responses (stimulation: episodes 31–61). Bottom: corresponding peri stimulus time histogram (PSTH). Note the temporal precision of the evoked spikes. Bin size 50 ms. (B) Same cell as in (A). The evoked inward current and the evoked spike both persisted in 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione (NBQX), D-2-amino-5-phosphonopentanoic acid (D-AP5), and mecamylamine but were blocked by gabazine. At least four traces are superimposed in each condition. (C) Another example of a PG cell responding to the photostimulation with action potentials. Photostimulation (blue arrow, episodes 31–65 in the raster plot) induced an outward current (inset) and, in some trials, a delayed doublet of spikes. Bottom: corresponding cumulative PSTH (bin size 50 ms). (D) Same cell as in (C). Gabazine blocked both the evoked outward current and the evoked spikes. (E) Distribution histogram of the average spike timing in each cell responding with spikes. Cells in which the stimulation evoked an inward capacitive current are in violet, and cells in which the stimulation evoked an outward current are in green. (F) Total number of cells responding with an inward (violet) or an outward (green) capacitive current followed or not with evoked spikes. (G) Whole-cell characterization of a cell excited by the BF input. Left: BF-evoked spike response (LCA recording, top, 20 consecutive episodes are superimposed) and BF-evoked IPSC (whole-cell recording, 20 consecutive responses). Right: current-clamp voltage responses to current steps in the same cell. The distribution histogram compares the decay time constants of photo-evoked GABAergic IPSCs in the seven PG cells that were excited (violet bars) vs. in type 2.2 cells with an inhibitory response (blue) and type 2.3 cells with a mixed GABA/ACh response (gray bars).