Pclamp software package

Local field potential (LFP) recordings were obtained in an interface chamber from the stratum pyramidale of the hippocampus (area CA3), the EC (mEC and lEC) and the temporal-associated cortex. Kainic acid (KA) (200 nM) was applied in the bath to induce network gamma frequency oscillations. Field oscillations were low-pass filtered at 1 kHz, digitized at 10 kHz (Digidata 1322, Axon Instruments), and analyzed with the pClamp software package (Axon Instruments). Oscillatory peak frequency was determined by averaging several consecutive Fourier transforms contained within a 20 to 30 s epoch. A Student´s t-test was used for statistical comparisons; differences were considered significant if p < 0.05. Average values are expressed as mean ± SEM.

Patch-clamp analysis was performed according to a previously published protocol [19 (link)], with slight experiment-specific adaptions. Procedures were conducted as follows. Electrophysiological recording was performed in a whole-cell configuration using an Axopatch 200A patch clamp amplifier (Axon Instruments, Foster City). Patch pipettes with resistances of 1 to 4 MΩ were made from borosilicate glass (GC150F-7.5, Clark Electromedical Instruments, UK) and filled with pipette solution. All data were digitized using a DIGIDATA 1200 interface (Axon Instruments, Foster City), smoothed by means of a four-pole Bessel filter, and saved to disc. Current traces were sampled at 10 kHz and filtered at 2 kHz. The pClamp software package (version 10.0 Axon Instruments, Inc.) was used for data acquisition. Microcal Origin 7.0 was used for analysis. If not otherwise mentioned, reagents were obtained from Sigma-Aldrich. Inward current of voltage-dependent Ca_v channels was evoked by applying 500-ms depolarizing pulses from a holding potential of − 50 to 50 mV. Superimposed current traces of K_v channels were evoked by step depolarizing pulses between − 80 and 60 mV in steps of 20 mV from a holding potential of − 80 mV in MPC, MPC-SMC, and hBd-SMC.

Extracellular DE-3 activity was recorded using a suction electrode placed on the distal end of the DP nerve; suction electrodes were made in-house, and had a tip diameter of ca. 50 μm. Signals were amplified by a Model 1700 A-M Systems differential A-C amplifier, and digitized by an Axon CNS Digidata 1440A (Molecular Devices). Intracellular sharp recordings of DE-3 activity were performed using glass electrodes pulled to a resistance of 25–60 MΩ with a micropipette puller (Sutter Instrument Co, model P-87) and filled with 2 m potassium acetate. Signals were amplified by an IX2-700 dual intracellular preamp (Dagan Corp.) and digitized as previously described. All signals were recorded with the pClamp software package (Molecular Devices), and imported into MATLAB (MathWorks) for analysis. Extracellular DE-3 activity was identified as the largest spontaneously active unit in the DP recording; somatic intracellular recordings were confirmed to be DE-3 by the cell’s size and position, and the correspondence of intracellular and extracellular spikes. The rising phase of the DE-3 extracellularly recorded action potential was typically negative in our recordings; extracellular traces in all figures were inverted for more intuitive viewing. By convention, we have omitted vertical scale bars from extracellular traces because of our use of an AC-coupled amplifier.