Layer-specific modulation of neuronal excitability by 660-nm laser irradiation in mouse neocortex.

It has been reported that laser light irradiation (LLI) could regulate neuronal activities in the forebrain, but little is known if and how LLI in the red wavelength range affects neuronal excitability. Here, we investigated the effects of a continuous diode laser at 660 nm on intrinsic membrane properties and excitability of presumed pyramidal neurons in the thalamocortical input layer (layer 3/4) and in layer 5 of mouse primary auditory cortex using the whole-cell patch-clamp recording technique. In layer 3/4 neurons, 660-nm laser irradiation (LLI-660) at 20 mW for 5 min gradually increased resting membrane potentials, which reached a plateau after irradiation.