INTRODUCTION: To use optogenetics in well control manner it is necessary to characterize the relation between the light power and resulting opening of light gated channels. AIM(S): To this end we tested the dependence of membrane depolarization on the parameters of light stimulation in channelrhodopsin-transfected neurones in rat’s central nucleus of amygdala (CeA). METHOD(S): Under general anesthesia rats were were injected with AAV-hSyn-ChR2-EYFP viral vector introducing ChR2 to CeA. During in vitro patch-clamp recording on brain slices, we measured the membrane depolarization evoked by a blue light emitted from LED source. Cells were stimulated with trains of light impulses with varying: 1) light power; 2) duration of light impulse; 3) frequency of light impulses. RESULTS: 1) Train of 2 ms light impulses delivered at 20 Hz, a driving current varying from 0.1 to 1 A: relation between light power and membrane depolarization can be approximated by a logarithmic function: 2.2 ln(x)+13 (at the resting potential kept at −50 mV) and 8 ln(x)+28 (at −60 mV). The dependency of the latency of first action potential on the light intensity can be approximated by a power function: 1.2 ×^(−1.3); 2) Train of light impulses of varying duration (range 2–20 ms) at 20 Hz, current 1 A and resting membrane potential kept at −50 mV: the relation between light impulse duration and resulting membrane depolarization can be approximated by a logarithmic function 3 ln(x)+4; 3) Train of 2 ms light impulses with a current set at 1 A and a frequency varying in a range 20–200 Hz (resting potential kept at −50 mV): relation between light impulse frequency and resulting membrane depolarization can be approximated by a logarithmic function: 2.5 ln(x)+3.5. CONCLUSIONS: Our results offers the guideline allowing to estimate expected depolarizing effects of light stimulation on the ChR2-transfected neuronal population in central nucleus of amygdala in rats. FINANCIAL SUPPORT: Supported by Polish National Science Centre grant 2013/08/W/NZ4/00691.
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