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. 2023 Sep 25;17:1254776. doi: 10.3389/fncel.2023.1254776

Figure 1.

Figure 1

Properties of synaptic connections between L4 and L2/3 pyramidal neurons. (A) Schematic representation of the experimental approach and some basal circuitry elements in the barrel cortex. The yellow arrow indicates the site of electric stimulation in L4, activating projections from spiny stellate neurons (SSN) toward both parvalbumin-interneurons (PV-IN) and pyramidal neurons (PN) in L2/3. (B) Typical current responses of a L2/3 pyramidal neuron (PN) upon suprathreshold electrical stimulation. The upper traces are recorded at a holding potential of-60 mV to isolate the glutamatergic component (EPSC). The middle and lower traces are recorded at 0 mV to isolate the GABAergic component (IPSC). Note that EPSCs are inhibited by the glutamatergic antagonists CNQX (10 μM) + APV (30 μM) and IPSCs by either CNQX (10 μM) + APV (30 μM) (middle traces) or the GABAergic antagonist gabazine (10 μM, lower traces). (C) Boxplots illustrating the properties of the EPSCs and IPSCs. (D) Input–output curve for EPSCs (red) and IPSCs (blue). The light traces represent responses from individual neurons and the bold traces depict mean values. (E) Typical voltage response of a L2/3 PyrN from a standard potential of −60 mV, illustrating the fast excitatory postsynaptic potential (EPSP), sculptured by the kinetics of the EPSC and the IPSC. (F) The voltage response recorded from a standard potential of −40 mV reveals the underlying GABAergic component of the response. Note the longer time scale in this plot. Significance is indicated by *p < 0.05 and ***p < 0.001.