A Computer-assisted Multi-electrode Patch-clamp System

Summary

Multi-electrode patch-clamp recordings constitute a complex task. Here we show how, by automating of many of the experimental steps, it is possible to accelerate the process leading to qualitative improvement in performance and number of recordings.

Abstract

The patch-clamp technique is today the most well-established method for recording electrical activity from individual neurons or their subcellular compartments. Nevertheless, achieving stable recordings, even from individual cells, remains a time-consuming procedure of considerable complexity. Automation of many steps in conjunction with efficient information display can greatly assist experimentalists in performing a larger number of recordings with greater reliability and in less time. In order to achieve large-scale recordings we concluded the most efficient approach is not to fully automatize the process but to simplify the experimental steps and reduce the chances of human error while efficiently incorporating the experimenter's experience and visual feedback. With these goals in mind we developed a computer-assisted system which centralizes all the controls necessary for a multi-electrode patch-clamp experiment in a single interface, a commercially available wireless gamepad, while displaying experiment related information and guidance cues on the computer screen. Here we describe the different components of the system which allowed us to reduce the time required for achieving the recording configuration and substantially increase the chances of successfully recording large numbers of neurons simultaneously.

Introduction

The capacity to record and stimulate multiple sites with micrometer precision is extremely useful for experimentally achieving a better understanding of neuronal systems. Many techniques have been developed to this end but none allow the submillivolt resolution achieved by the patch-clamp technique, essential for studying subthreshold activity and individual postsynaptic potentials. Here we cover the development of a twelve-electrode computer-assisted patch-clamp system aimed at simultaneously recording and stimulating a large number of individual cells with sufficient precision for the study of neuronal connectivity. While many other applications can be conceived for....

Protocol

1. Equipment Preparation

1. Control manipulators from a computer
   1. Connect each micromanipulator controller box to a computer through serial ports (RS-232).
   2. Implement the commands for positioning, querying and adjusting settings to be sent via the serial port. Given speed and hardware compatibility issues C/C++ is recommended as the programming language.
   3. Standardize the reference system of the manipulators so that zero is the closest possible position with respect to the motors and positive movement is directed away from the motors.
   4. Position the microscope at its central position 2 mm above the speci....

Results

Following the methods described above we succeeded in performing whole-cell recording of up to twelve neurons simultaneously, nearly doubling the largest number of neurons simultaneously patch-clamped thus far. Examples of networks of direct synaptic connections between Pyramidal Neurons recorded in Layer V of the somatosensory cortex of rats are shown in Figure 6.

The determination of connection probability profiles as a function of inter-somatic distance for a given cell-typ.......

Discussion

An immediate question usually arises concerning the rate of success of the procedure we described. For high success rates preparation is essential. Pipettes must have tip openings that are adequate for the cells beings recorded. Filtering the intracellular solution to avoid clogged pipettes is also important. Extremely clean, freshly pulled pipettes are another requirement. A binomial distribution is the simplest model that can be used to understand how these issues affect the final yield. It is reasonable to expe.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Microscope	Olympus	BX51WI	40X Immersion Objective
Manipulators	Luigs Neumann	SM-5	Serial protocol used
Amplifiers	Axon Instruments	MultiClamp 700B	SDK used
Camera	Till Photonics	VS 55	BNC analog output
Framegrabber	Data Translation	DT3120	SDK used
Oscilloscopes	Tektronix	TDS 2014	Serial communication
Data acquisition	InstruTECH	ITC 1600
Data acquisition	National Instruments	PCI-6221	Library used (.dll)
Pressure valve	SMC	SMC070C-6BG-32
Pressure sensor	Honeywell	24PCDFA6G
Membrane pump	Schego	Optimal