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.