Fig. 5: Ketamine induces a sustained loss of excitatory inputs to PV neurons, which is restored with NRG1.
A Schematic depicting the medial prefrontal cortex (mPFC) region of mouse brain from which recordings were taken. B Schematic of laser-scanning photostimulation (LSPS) mapping of cortical synaptic connections to individually recorded PV neurons in mPFC slices. LSPS maps the broad spatial pattern of synaptic inputs to the neuron of interest, and distinguishes direct uncaging responses (1, red) to assess glutamate-mediated excitability/responsiveness at perisomatic locations, and synaptically mediated EPSC responses (2, cyan) to assess synaptic inputs from presynaptic neuronal spiking. Cortical layers of 1, 2/3, 5, and 6 in the brain slice are indicated as L1, L2/3, L5, and L6. Recorded PV neurons are filled with biocytin for post-hoc confirmation. C Group-averaged, excitatory input maps of PV cells recorded at the specified conditions. White circles in each map represent individual PV neurons. The color scales code integrated excitatory input strength (blue = low, red = high) and applies to all other maps in the same condition. C (left column) An acute bath application of NRG1 (5 nM) does not significantly modulate local excitatory synaptic inputs onto PV neurons in mPFC of saline-treatment control mice. Averaged excitatory input maps of L2/3 PV cells are shown before (top), during bath NRG1 (20 min after NRG1 application) (middle), and after washout of bath NRG1 (bottom). C (right columns) Reduced excitatory inputs to PV neurons are seen at 1, 24, 48, and 72 h after ketamine treatment (10 mg/kg; s.c.), but not after 1 week. Excitatory inputs to PV neurons in ketamine-treated mice are restored by acute bath application of NRG1. This acute restoration by NRG1 is eliminated by washout of the bath NRG1. D Summary data of average total synaptic input strength measured for L2/3 PV neurons under the specified conditions (control, 1, 24, 48, and 72 h and 1 week after ketamine treatment) (Linear mixed effects model (two factors): highly significant. Two-sample t test (adjusted for multiple comparisons): base vs base (control), 1 h p = 0.0057, 24 h p = 2.76 × 10−4, 48 h p = 7.54 × 10−4, 72 h p = 1.42 × 10-4, 1 week p = n.s. Paired sample t test (adjusted for multiple comparisons): NRG1 vs base, 1 h p = 0.054, 24 h p = 7.23 × 10−5, 48 h p = 2.38 × 10−4, 72 h p = 1.82 × 10−4, 1week p = n.s.; mean ± SEM). E Direct uncaging responses before and during bath NRG1 for PV neurons in control versus ketamine-treated mice. Peak direct responses were measured, which are not affected by overriding synaptic inputs (Linear mixed effects model (two factors): highly significant; Two-sample t test (adjusted for multiple comparisons): base vs base (control), 1 h p = 0.0032, 24 h p = 1.96 × 10−4, 48 h p = 0.012, 72 h p = 3.77 × 10−4, 1wk p = n.s.; Paired sample t test (adjusted for multiple comparisons): NRG1 vs base, 1 h p = 0.0095, 24 h p = 2.63 × 10−4, 48 h p = 7.95 × 10−4, 72 h p = 2.92 × 10−4, 1 week p = n.s.; mean ± SEM).
