Patch & Current Clamp in 300µm Medial Prefrontal Cortex Slices cut with 7000smz-2

Abstract

(from Excitatory synapses and gap junctions cooperate to improve Pv neuronal burst firing and cortical social cognition in Shank2-mutant mice, Lee et al, 2021)

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NMDA receptor (NMDAR) and GABA neuronal dysfunctions are observed in animal models of autism spectrum disorders, but how these dysfunctions impair social cognition and behavior remains unclear. We report here that NMDARs in cortical parvalbumin (Pv)-positive interneurons cooperate with gap junctions to promote high-frequency (>80 Hz) Pv neuronal burst firing and social cognition. Shank2–/– mice, displaying improved sociability upon NMDAR activation, show impaired cortical social representation and inhibitory neuronal burst firing. Cortical Shank2–/– Pv neurons show decreased NMDAR activity, which suppresses the cooperation between NMDARs and gap junctions (GJs) for normal burst firing. Shank2–/– Pv neurons show compensatory increases in GJ activity that are not sufficient for social rescue. However, optogenetic boosting of Pv neuronal bursts, requiring GJs, rescues cortical social cognition in Shank2–/– mice, similar to the NMDAR-dependent social rescue. Therefore, NMDARs and gap junctions cooperate to promote cortical Pv neuronal bursts and social cognition.

Method

Slice electrophysiology

Mice were anesthetized with isoflurane and decapitated. After brain dissection, coronal slices containing the medial prefrontal cortex (300 µm) were cut in ice-cold oxygenated sucrose-based cutting solution containing (in mM): 75 sucrose, 76 NaCl, 2.5 KCl, 25 NaHCO3, 25 glucose, 1.25 NaH2PO4, 7 MgSO4, 0.5 CaCl2 with pH 7.3, equilibrated with 95% O2 and 5% CO2, using a vibratome (7000smz-2, Campden Instruments), and then recovered in the same solution for 30 min at 33–34 °C. Slices were then transferred to an incubation chamber filled with oxygenated artificial cerebral spinal fluid (ACSF) containing (in mM): 124 NaCl, 2.5 KCl, 1.3 MgCl2, 2.5 CaCl2, 1.0 NaH2PO4, 26.2 NaHCO3, 20 glucose with pH 7.4 at room temperature and slices were kept in <7 h before recordings.