Figure 8. Inhibitory synapses from Pv and Sst interneurons are differentially impaired in Stxbp1^tm1d/+ mice.

(A) uIPSCs of a layer 2/3 pyramidal neuron (V_m = + 10 mV) in the somatosensory cortex (upper panels) evoked by a train of 10 Hz action potentials in a nearby Pv interneuron (lower panels) from WT and Stxbp1^tm1d/+ mice. 50 individual traces (lighter color) and the average trace (darker color) are superimposed. Note smaller uIPSCs in the Stxbp1^tm1d/+ neuron. (B) Unitary connectivity rates from Pv interneurons to pyramidal neurons were similar between WT (27 connections out of 33 pairs) and Stxbp1^tm1d/+ (26 connections out of 32 pairs) mice. (C) Cumulative frequencies of uIPSC amplitudes evoked by the first action potentials in the trains (median: WT, 217.3 pA; Stxbp1^tm1d/+, 127.1 pA). Inset, each filled (male) or open (female) circle represents the uIPSC amplitude of one synaptic connection. (D) uIPSC amplitudes during the trains of action potentials were normalized by the amplitudes of the first uIPSCs. Note the similar synaptic depression between WT and Stxbp1^tm1d/+ neurons. (E–H) Similar to (A–D), but for Sst interneurons. Unitary connectivity rates from Sst interneurons to pyramidal neurons (F) in Stxbp1^tm1d/+ mice (25 connections out of 36 pairs) were less than WT mice (34 connections out of 36 pairs). The uIPSC amplitudes evoked by the first action potentials in the trains (G, median: 83.5 pA and 68.0 pA, respectively) and synaptic depression (H) were similar between WT and Stxbp1^tm1d/+ mice. The ages of mice are indicated in the figures. Bar graphs are mean ± s.e.m. n.s., p>0.05; *, p<0.05; **, p<0.01.

Figure 8—figure supplement 1. Intrinsic neuronal excitability of Stxbp1^tm1d/+ mice is slightly increased.

(A) Membrane potentials (upper panels) in response to current injections (lower panels) in layer 2/3 pyramidal neurons of the somatosensory cortex from WT and Stxbp1^tm1d/+ mice. (B–D) Summary data showing that Stxbp1^tm1d/+ neurons had similar resting membrane potentials and rheobase currents as WT neurons, but their input resistances were 19% larger than WT neurons. The numbers and ages of recorded neurons are indicated in the figures. Each filled (male) or open (female) circle represents one neuron. Bar graphs are mean ± s.e.m. n.s., p>0.05; *, p<0.05.

Figure 8—figure supplement 2. Spontaneous excitatory inputs onto Pv and Sst interneurons are unaltered in Stxbp1^tm1d/+ mice.

(A,B) sEPSCs of a Pv (A) or Sst (B) interneuron (V_m = –70 mV) in the layer 2/3 of the somatosensory cortex from WT or Stxbp1^tm1d/+ mice. (C,D) Summary data showing that the frequency and amplitude of sEPSCs in Pv (C) and Sst (D) interneurons are similar between WT and Stxbp1^tm1d/+ mice. The numbers and ages of recorded neurons are indicated in the figures. Each filled (male) or open (female) circle represents one neuron. Bar graphs are mean ± s.e.m. n.s., p>0.05.