Figure 2. Light-induced hyperpolarization of cholinergic neurons transiently decreases the frequency and alters the phasing of drug-induced locomotor-like activity.

(A) Locomotor-like activity recorded from the right L2 and left L2 and L5 ventral roots (black traces) of a P1 isolated spinal cord of a ChAT-Arch mouse. The superimposed green traces are the slow potentials obtained by low pass filtering the raw signals. Locomotor-like activity was evoked by applying 5 μM NMDA and 10 μM 5-HT. The duration of the light (60 s) is indicated by the green bar. (B–C) Time series showing the change in absolute phase (B) and frequency (C) averaged for all experiments for the bilateral flexor (B1–C1) and the ipsilateral flexor/extensor roots (B2–C2). (D) Change (%) in the averaged integrated ventral root discharge (Change in MN firing) for the ipsilateral flexor (D1) and extensor (D2) ventral roots. The statistics were obtained using a bootstrap t-test between ChAT-Archaerhodopsin (n = 25) and wild type cords (n = 28) and are color-coded as indicated in the box below the records.

DOI: http://dx.doi.org/10.7554/eLife.26622.003

Figure 2—figure supplement 1. Effect of green light on drug-induced locomotor-like activity in wild type cords.

(A) Ventral root recordings (Right L2, and Left L2 and L5) showing the effect of light on the locomotor-like rhythm evoked by 5 μM NMDA and 10 μM 5-HT in a wild type cord. The superimposed yellow traces are the slow potentials obtained by low pass filtering the raw signal. The green bar indicates the duration of the light (60 s). (B–C) Time series of the change in absolute phase (B) and frequency (C) averaged for all experiments for the bilateral flexors (B1 and C1) and the ipsilateral flexor-extensors (B2 and C2) in 28 wild-type cords. (D) Averaged integrated signals (Change in MN firing) for the ipsilateral flexor (D1) and extensor (D2) ventral roots. The dotted lines on the traces represent ±1 standard deviation of the mean. The green light (green rectangles) causes an increase in the firing of motoneurons in both the bilateral flexors and the ipsilateral flexor/extensor roots. Accompanying this is a small increase in the frequency of the locomotor-like rhythm.

DOI: http://dx.doi.org/10.7554/eLife.26622.004

Figure 2—figure supplement 2. Effect of varying the green light intensity on the integrated firing of the right L2 ventral root and on the frequency of the locomotor-like rhythm in ChAT-Arch cords.

(A–B) Bar plots showing the average change in motoneuron firing (A, Change in MN firing) and frequency of the right L2 (B) for the 10 s just before and just after the light is turned on (Start Light, circles) and the 10 s just before and just after the light is turned off (After Light, squares). The color gradient of the bars indicates the intensity of the light from black 100%, to light grey 20–25%. (C–D) Bar plots showing the averaged change in motoneuron firing (C, Change in MN firing) and in the frequency of the right L2 (D) for the 10 s just before and just after the light is turned on (Start Light, circles) and the 10 s just before and just after the light is turned off (After Light, squares). Either the ventral (black and grey bars) or the dorsal (orange and light orange bars) part of the cord was illuminated either at 100% intensity (C1, D1, black and orange respectively) or at 20–25% intensity (C2, D2, grey and light orange respectively). Using a two-way ANOVA, we calculated the statistical differences between the different light intensities (shown above the bars in A, *p<0.05, **p<0.01) and site of illumination (dorsal or ventral in C-D). ANOVA for the changes in frequency at the beginning of the light (Site of illumination: F(1,52)=0.1705, p=0.6814, Light intensity: F (5,52)=0.932, p<0.4680, Interaction F(5,52)=0.3916, p=0.8523) and after the light is turned off (Site of illumination: F(1,52)=0.5472, p=0.4628, Light intensity: F (5,52)=2.823, p<0.4680, Interaction F(5,52)=0.5886, p=0.7086) and the two-way ANOVA results for the change in motoneuron firing at the beginning of the light were (Site of illumination: F(1,52)=5.276, p=0.0257, Light intensity: F(5,52)=2.695, p<0.0307, Interaction F(5,52)=0.2178, p=0.9534) and after the light (Site of illumination: F(1,52)=0.3265, p=0.5702, Light intensity: F(5,52)=3.216, p<0.0132, Interaction F(5,52)=0.2178, p=0.9534).

DOI: http://dx.doi.org/10.7554/eLife.26622.005