Localized two-photon photoswitching of Optovin in rat cortical neurons

Photoswitching molecules are widely used to control neuronal activity by activation of endogenous cellular channels and receptors. Optovin is a photoswitching molecule that targets the cation channel transient receptor potential ankyrin 1 (TRPA1). In zebrafish, bulk single-photon photoswitching of Optovin produced behavioural responses associated with TRPA1 activation. We recently found that TRPA1 is widely expressed in the rodent brain particularly in cortical pyramidal neurons and demonstrated its functional activation via TRPA1 agonists and by two-photon (2P) photoswitching of Optovin in the soma. Here, we exploit the highly localized 2P photoswitching of Optovin to activate TRPA1 along different dendritic and axonal regions of individual pyramidal neurons in the rodent cortex. The technique facilitates measurement of isolated responses when light is directed to the axon and along various dendritic domains of L5 pyramidal neurons. Using this technique, we show that 2P photoswitching of Optovin results in higher levels of depolarization along the base of the apical trunk compared to any other location in the neuron.