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.