OptoPatcher

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In order to perform simultaneous intracellular recording and light stimulation of a single neuron, two separate positioning systems are often needed (one to position the recording electrode, one to position a waveguide near the recorded neuron). More sophisticated solutions for single neuron photostimulation involve light patterning techniques which are not suited for deep in vivo recordings. Katz et al. came up with a simple and affordable solution for this problem, by designing a patch pipette holder containing an additional port for the insertion of an optical fiber into the pipette.

This device, which they called “OptoPatcher” allows whole cell patch-clamp recording simultaneously with direct projection of light from the recording pipette. The holder spares the use of an additional manipulator and, importantly, enables accurate, stable and reproducible illumination. Moreover, the presence of the bare fiber within an aqueous solution instead of the brain can prevent tissue damage due to heating of the brain. In addition, replacement of standard pipettes is done as easily as with the available commercial holders.

The OptoPatcher was used successfully in vivo for intracellular recordings from different cortical layers in the motor cortex of transgenic mice expressing channelrhodopsin-2 under the Thy1 promoter and it was also used in-vitro for NMDA uncaging using UV flash.

The OptoPatcher electrode holder.
The properties of the optopatcher. (A) Drawing of the electrode holder. The bare optical fiber is inserted through the optic fiber port into the glass pipette which is inserted at the pipette connector. (B) Light transmission through the brain was measured by mounting a brain slice on a cover glass and advancing the electrode into the tissue. (C) Light intensity was reduced on average by about 70% at 1000 μm depth (n = 15). (D and E) Beam profile in saline (D) and cortex (E). Images are sections of a 3D map along the illumination axis trough the pipette's tip and are normalized to the maximal intensity. Notice the decreased light transmission in the center of the beam profile in saline which results due the glass pipette. From Katz et al, 2013.