Functional Organization of Locomotor Interneurons in the Ventral Lumbar Spinal Cord of the Newborn Rat
Figure 2
A, Photomicrographs showing Fluo-4 AM labeling in the in vitro ventral SC preparation at the T13-L1 level (A1, magnification ×4; scale bar = 200 µm). Right photomicrographs were taken from areas delineated by grey squares 1 and 2 (A2, A3, magnification ×10; Scale bar = 100 µm). B, Extracellular recordings of left L2 VR and its rectified and low-pass filtered trace illustrating a typical rhythmic activity. Grey bars are aligned with r L2 VR bursts and reveal three cells examples tending to have Ca2+ peaks in phase (cell1), out of phase (cell2) or mixed (cell3) with lL2 VR activity. C, Circular plots illustrating the Ca2+ peak phases (black circles) for each cell in relation to the timing of L2 VRs bursts. The mean VR bursts over a 60 s recording bout range from spans phases 0 to 0.4 in the circular plot and is illustrated in grey. Vectors show the mean phase values and r values. Vector orientation indicates preferred phase of firing; vector length is proportional to coupling strength. D, Dot diagram shows distribution of all cells with phase relationship with motor output from T12 to L5. Cells were illustrated in phase (red dots), out of phase (black dots) and mixed (grey dots). E, Density plot of in phase and out of phase cells from T12 to L5 segments (n = 4 experiments; cc: central canal; scale bar = 100 µm).