A versatile and modular tetrode-based device for single-unit recordings in rodent ex vivo and in vivo acute preparations.

Background: The demand for affordable tools for recording extracellular activity and successfully isolating single units from different brain preparations has pushed researchers and companies to invest in developing and fabricating new recording devices. However, depending on the brain region of interest, experimental question or type of preparation, different devices are required thus adding substantial financial burden to laboratories.

New Method: We have developed a simple and affordable tetrode-based device that allows interchangeable extracellular recordings of neuronal activity between in vivo and ex vivo preparations and can be easily implemented in all wet-bench laboratories.

Results: Spontaneous activity from several putative single neurons could be easily recorded and isolated by lowering the device into ex vivo cerebellum brain slices. The same device was also used in vivo, lowered into primary auditory cortex of adult anesthetized transgenic mice expressing channelrhodopsin in cortical neurons. Acoustic stimulation of the contralateral ear or direct laser optogenetic stimulation successfully evoked cortical activity at the recording site. Several isolated putative single neurons presented time-locked activity response to the different stimuli.

Comparison With Existing Methods: Besides low fabrication cost, our device uses an omnetics connector compatible with the majority of headstages already available at most electrophysiology laboratories. The device allows custom tetrode configuration arrays and extensions for optogenetics and pharmacology, providing experimental flexibility not available in commercial off-the-shelf microelectrode arrays and silicon probes.

Conclusions: We developed an affordable, versatile and modular device to facilitate tetrode extracellular recordings interchangeably between in vivo anaesthetized animals and ex vivo brain slice recordings.