Procedure 3: Determination of light effect on membrane currents
Cells were held at -60 mV in voltage-clamp mode. The stimulation pattern was repeated three time at 10 s intervals for the three powers (1mW, 5mW, and 13mW). The discontinuous light patterns were followed, after 10 s, by 1 s of continuous light stimulation. Since 1 s stimulation was expected to produce a consistent outward current (Ait Ouares et al. , 2019), the effect of continuous stimulation was used as positive control. In the protocols for which the total illumination time (T.I) during patterned stimulation was different than 1s, a continuous T.I. light step was also applied. Fifteen electrophysiological traces were recorded for each neuron, these were aliened on the pre-light control period and a median trace was calculated. The light effect was quantified on the median trace by subtracting, for each of the 50 light steps, the average membrane current in the 1 s preceding the application of light (the CTR period) from the average membrane current during light period. Only one of the ten stimulation patterns was applied on each MC. Procedures 2 and 3 were performed on the same electrophysiological acquisition.