Figure 2.
The location of HRP-labeled motoneuron somas at St 27 in chronic picrotoxin-treated embryos and in embryos treated with picrotoxin but activated via ChR2 at intervals of 40 s. A, B, Sixteen micrometer cross sections of spinal cord, revealing the location of cell bodies immunolabeled with antibodies against HRP when ventral (A) or dorsal (B) nerve trunks where injected with HRP in chronic picrotoxin-treated embryos. White arrows and arrowhead highlight misplaced motoneurons. C, D, HRP immunostaining of 16 μm spinal cord cross sections of embryos that underwent light activation by ChR2 in addition to chronic picrotoxin treatment. E, Schematic representing dorsal and ventral projections of LMCL and LMCM motoneurons, respectively, as well as the transcription factor expression in the cell bodies of these motoneurons. F, A bar graph depicting the number of misplaced motoneurons as a percentage of all labeled HRP-positive motoneurons per side in 16 μm sections of the lumbar spinal cord (see Materials and Methods). Light activation by ChR2 in addition to chronic picrotoxin treatment prevented misplaced cell bodies that occurred in chronic picrotoxin-treated embryos. Light activation by ChR2 at control intervals reduced the large numbers of misplaced motoneurons observed in picrotoxin-treated embryos to control values, which are very low (*p < 0.025). Scale bar, 50 μm. Chr. Picro, Chronic picrotoxin treatment.