Figure 4. Miro1 knock-out does not alter spontaneous and evoked inhibitory synaptic transmission in the hippocampus.

(A) Representative electrophysiological traces of spontaneous inhibitory post-synaptic currents from WT (black) and Miro1 KO (red) cells in the hippocampus. (B) Quantification for the mean inter event interval (IEI). (C) Quantification for the median sIPSC amplitude. (n_WT = 13 recordings, two animals and n_KO = 12 recordings, two animals). (D) Generation of the Pvalb^Cre Rhot1 ChR2-EYFP transgenic mouse line. Schematic diagram of the expression of ChR2-EYFP and simultaneous conditional removal of Rhot1. When the Cre recombinase is expressed, under the PV+ promoter, the stop-floxed codon is excised from the Rosa26 locus allowing the downstream expression of ChR2-EYFP. Additionally, the second exon of the Rhot1 gene is found between two loxP sites and also removed selectively in PV+ interneurons. (E) Example of confocal image from a biocytin-filled recorded pyramidal cell in the hippocampus (red) in close proximity to an EYFP+ PV+ interneuron (green). Scale bar = 10 μm. (F) Representative traces from light evoked inhibitory postsynaptic current (eIPSC) in WT (black) and Miro1 KO (red) cells in acute brain slices (n_WT = 23 recordings, four animals and n_KO = 23 recordings, four animals). (G) Boxplot for the quantification of peak amplitude. (H) Boxplot for the quantification of charge transfer. (I) Boxplot for the quantification of decay. (J) Control and conditional knock-out cells can sustain inhibition and recover with similar rates after long-lasting photostimulation. Example traces from the inhibitory responses pyramidal cells received in WT and Miro1 KO slices during light train stimulation (40 Hz for 2 s; 1 ms pulse width). (K) Mean amplitude of each peak during the light train stimulation (n_WT = 21 recordings, four animals and n_KO = 24 recordings, four animals). (L) Quantification of the percentage recovery after light stimulation of all cells at increasing time intervals from the end of the light train (n_WT = 21 recordings, four animals and n_KO = 18 recordings, three animals).

Figure 4—figure supplement 1. Intrinsic properties of PV+ interneurons in the absence of Miro1.

(A) Representative traces of the firing patterns of WT, ΗΕT, and Miro1 KO cells in response to 200 pA current injection (n_WT = two animals, n_ΗΕT = four animals, n_KO = five animals). (B) Quantification of the action potential peak amplitude. (C) Quantification of the action potential half-width. (D) Quantification of Spike Rate at RheoBase +40 pA. Cells that fire less than five spikes were excluded from the quantification. (E) Quantification of input resistance. (F) Quantification of threshold to fire. (G) Quantification of time constant. White circles in bar graphs represent recordings from individual cells.