Sutter IPA amplifiers

The Sutter Instrument IPA and double IPA (dIPA) devices combine the data acquisition hardware and the amplifiers in one device. MIES controls these amplifiers from the DA_Ephys panel in the same way as MultiClamp 700B amplifiers, with the differences described below.

Requirements

• The Sutter XOP (SutterXOP, version 2.60) must be installed. Without it MIES can not use Sutter devices and the amplifier control procedures IPA_Control.ipf from Sutter Instrument are not loaded.

• There is no separate amplifier control software like the MultiClamp Commander. The amplifiers are initialized when the device is locked in the DA_Ephys panel and released when it is unlocked. Locking resets the amplifier settings, see Settings when locking.

• If the amplifiers can not be initialized, e.g. due to an incompatible Sutter XOP or a missing connection, a message is printed and the device is still locked, as for MCC amplifiers without a running MultiClamp Commander. The amplifiers can then not be used, test pulse and data acquisition on their headstages are refused. Unlock and lock the device again to retry the initialization.

Headstages and amplifier assignment

Each probe of the connected IPA devices is one MIES headstage, in the order of the devices and, for a double IPA, its first and second headstage. The DA channel, AD channel and amplifier of each headstage are fixed and assigned automatically when locking the device. Therefore the following controls of the Hardware tab are disabled for Sutter devices: the DA/AD channel popups, Amplfier (700B), Clear Associations and Query connected Amp(s).

Gains and units

The Sutter XOP outputs and acquires the headstage signals in SI units, so the gains and units of the headstages are fixed:

Clamp mode	DA gain and unit	AD gain and unit
V-Clamp	1000 mV/V, command in mV	1e-12 A/pA, current in pA
I-Clamp	1e12 pA/A, command in pA	1e-3 V/mV, voltage in mV

Auto Fill in the Hardware tab fills in these fixed values. The gain setting of the amplifier does not change them, it only selects the input range and resolution, see Settings without GUI controls.

Clamp modes

V-Clamp and I-Clamp are supported. I=0 is not supported by the Sutter amplifiers, its controls and Mode switch via I=0 are disabled for Sutter devices.

In I-Clamp the command output range of the headstages is +/-20 nA. The DAScale of a stimulus set is limited accordingly, analysis functions report a future DAScale value out of that range, as the output range of the Sutter amplifiers can not be changed.

Amplifier controls

The amplifier controls of the Data Acquisition tab work for Sutter amplifiers, with these differences:

Control	Behaviour with Sutter amplifiers
Holding potential (V-Clamp)	1 mV resolution.
Holding current (I-Clamp)	1 pA resolution, limited to +/-20 nA.
Pipette offset	The amplifier has one pipette offset for both clamp modes, changing it in one clamp mode also changes it in the other one. The range is -250 mV to +249.98 mV. The automatic pipette offset (Auto) is meant to be used with the pipette in the bath.
Bridge balance	0 to 200 MΩ. There is no automatic bridge balance, its Auto button is disabled.
Capacitance neutralization (I-Clamp)	0 to 25 pF. The amplifier uses the same value as the fast capacitance compensation in V-Clamp, changing one of them also changes the other one.
Cp Fast	Automatic fast (electrode) capacitance compensation, to be used in the cell attached configuration. The amplifier applies the result immediately.
Cp Slow	Not available, the button is disabled.
Whole cell compensation	Capacitance 0 to 100 pF, resistance 0 to 100 MΩ, only active in V-Clamp. The automatic whole cell compensation (Auto) requires the fast capacitance compensation (Cp Fast) first. It also sets the bridge balance to the resulting series resistance.
Rs compensation	The enable checkbox enables correction and prediction together. Chain works as for MCC amplifiers.
Auto Bias	Works as for MCC amplifiers.

Settings which the amplifier changes as a side effect, like the pipette offset of the other clamp mode, are updated in the DA_Ephys panel after writing a setting.

Settings without GUI controls

The following amplifier settings have no control in the DA_Ephys panel yet. They can be set with IPA_SetValue(probe, setting, value) of the IPA control procedures on the Igor Pro command line, where probe is the headstage number plus one. They are documented in the labnotebook with every sweep.

Setting	IPA_SetValue keyword	Remarks
Primary output low pass filter	Filter	500 Hz, 1 kHz, 2 kHz, 5 kHz, 10 kHz or 20 kHz, one filter for both clamp modes. Other values are rounded to the next one, there is no bypass.
Primary output gain	IGain (V-Clamp), VGain (I-Clamp)	0.5 to 25 mV/pA in V-Clamp and 10 to 500 mV/mV in I-Clamp. As the data is acquired in SI units, the gain only selects the input range of +/-10 V divided by the gain and the resolution. Large gains therefore clip the signal, e.g. with VGain 500 the I-Clamp input is limited to +/-20 mV.
Dynamic hold	DynHoldOn, DynHold	I-Clamp only, keeps the membrane potential at the given level by a slow current injection.

Settings when locking

The IPA control procedures store the amplifier settings in their package preferences on disk. To start with a defined state, MIES resets all amplifier settings to their defaults when locking a Sutter device, instead of applying the settings of the previous session:

• holding potential and holding current, pipette offset, bridge balance, capacitance neutralization, whole cell compensation and Rs compensation are zero and disabled, the fast capacitance compensation is 0.1 pF

• dynamic hold is off

• the primary output filter is 5 kHz, the gain is 5 mV/pA in V-Clamp and 100 mV/mV in I-Clamp

The amplifier controls of the DA_Ephys panel are updated to this state, so that the panel shows the settings of the amplifier. Settings changed with IPA_SetValue during a session therefore have to be set again after locking the device.

Labnotebook

Settings of Sutter amplifiers with an MCC counterpart use the existing amplifier labnotebook entries, see Labnotebook descriptions. The following entries are only written for Sutter amplifiers:

• V-Clamp Output Gain, I-Clamp Output Gain

• RsComp Lag

• Dynamic Hold Enable, Dynamic Hold Level

• Amplifier Serial Number (text)

The entries only available for MCC amplifiers, like the slow capacitance compensation, are not written. Except for the clamp mode, which is read back from the amplifier, the values are the settings sent to the amplifier, as the Sutter amplifiers can not report their settings.

Configuration files

The headstage association of a DA_Ephys configuration stores the amplifier type of each headstage. For Sutter amplifiers only the amplifier type and the probe are stored, as the amplifier settings can not be restored yet. When restoring a configuration:

• The Sutter amplifiers keep their fixed assignment. A configuration with MCC amplifiers can therefore be restored on a Sutter device, the headstages then keep their Sutter amplifier and a message is printed.

• The restore aborts if the Sutter probe stored for a headstage does not match the connected IPA devices.

Analysis functions

• The analysis function parameter AmpBesselFilter of PSQ_Chirp() only accepts the low pass filter values of the Sutter amplifiers listed above and no Bypass.

• Sutter devices have four asynchronous channels.

• Requesting the automatic bridge balance via the foreign function interface aborts for Sutter amplifiers.

Known limitations

• The double IPA is supported by the headstage assignment, but has not been tested with hardware yet.