Figure 3. In dlx5/6 mice, a single photostimulation of basal forebrain (BF) axons evokes a biphasic inhibition-excitation response in periglomerular (PG) cells with a muscarinic excitation.

(A) Schematic of the virus injection in the horizontal limb of the diagonal band of Broca/magnocellular preoptic nucleus (HDB/MCPO) of dlx5/6^Cre mice. (B) ChR2-eYFP expression in BF axons (yellow) in a sagittal section of the olfactory bulb (OB). DAPI staining (blue) delimits the different layers (GL: glomerular layer; EPL: external plexiform layer; MCL: mitral cell layer; GCL: granule cell layer). Scale bar 100 µm. Higher-resolution image in Figure 3—figure supplement 1. (C) Representative spiking response, raster plot, and cumulative peri stimulus time histogram (PSTH) (10 consecutive sweeps, 200 ms/bin) of a typical biphasic inhibition-excitation response evoked by a single photostimulation of BF fibers and recorded over 15 s in a PG cell from a dlx5/6 mouse. (D) Average spiking frequency per bin (200 ms) and per episode. Each gray line corresponds to a cell. The black line is the ensemble average. Photostimulation at blue arrow. Only one cell in the dataset responded with a long-lasting excitation that was not preceded by an inhibitory component (Figure 3—figure supplement 3). (E) The nonselective muscarinic ACh receptor (mAChR) antagonist atropine (10 µM) blocked BF-evoked excitation. (F) Firing rate before (pre) and after (post) photostimulation of BF axons in artificial cerebrospinal fluid (ACSF) (green) in the presence of 6-nitro-7-sulfamoylbenzo[f]quinoxaline-2,3-dione (NBQX), D-2-amino-5-phosphonopentanoic acid (D-AP5), and mecamylamine (violet) or in the presence of the muscarinic receptor antagonist atropine (n = 7) or scopolamine (n = 2) (red). Each line indicates a cell. Blue circles indicate means. Paired t-test.

Figure 3—figure supplement 1. Higher-resolution image of Figure 3B showing the distribution in the olfactory bulb (OB) of a dlx5/6 mouse of eYFP-expressing axons from basal forebrain (BF) cholinergic and GABAergic neurons.

The two channels used to make this image are shown on top.

Figure 3—figure supplement 2. Basal forebrain (BF) inputs have various impacts on periglomerular (PG) cells activity in dlx5/6 mice.

(A) Example of an inhibitory response. In this cell, photostimulation of the BF fibers (blue arrow, 1 ms flash, 490 nm) transiently inhibited spiking. Top: a representative 2-s-long loose cell-attached (LCA) recording episode (scale bar 20 pA). Middle: cumulative peri stimulus time histogram (PSTH) (bin size 20 ms) in the same cell for 30 consecutive episodes with stimulation. Bottom: raster plot showing spiking activity in control condition (episodes 0–30) and while BF axons were photostimulated once per episode with a single flash (episodes 31–60, blue line). (B) Example of an excitatory response where BF fibers photostimulation (episode 27–55) induced an inward current and a spike (red star in the inset). Scale bar 30 pA. Corresponding PSTH and raster plot, same as in (A). (C) Example of a dual inhibition-excitation response where BF axons photostimulation inhibited spiking after the flash but also induced a muscarinic increase in baseline firing rate (see raster plot). Scale bar 200 pA. PSTH and raster plot, same as in (A) and (C). (D) Probability of occurrence of the various types of LCA responses induced on PG cells firing by a single optogenetic stimulation of the BF axons.

Figure 3—figure supplement 3. the unique example, in a dlx5/6 mouse, of a cell responding with a long-lasting excitation that was not accompanied by a transient inhibitory phase immediately after the flash.