Figure 2.
Retrograde propagation of BoNT/A effects in the limbic system. A, Immunoblotting for BoNT/E-cleaved SNAP-25 [cl. S-25(E)] on protein extracts from the injected hippocampus at different times after BoNT/E injection. BoNT/E effects are extinguished by 21 d. Fifteen micrograms of protein were loaded per lane. β-Tubulin, Internal standard. B, Persistence of BoNT/A-truncated SNAP-25 in the injected hippocampus. Levels of BoNT/A-cleaved SNAP-25 [cl.S-25(A)] remain high for up to 120 d after injection and decrease at 180 d. C, Unilateral BoNT/E administration results in SNAP-25 cleavage in the injected (ipsi) but not contralateral (contra) hemisphere. D, Appearance of BoNT/A-truncated SNAP-25 on the side contralateral to the injection starting from 3 d after toxin delivery. E, Hippocampal coronal section from a mouse unilaterally injected with BoNT/A 3 d earlier. Staining for cleaved SNAP-25 (red) is evident in both hemispheres. Green, Neuronal counterstaining (NeuN antibody). Arrows indicate stratum oriens (s.o.) and radiatum (s.r.). Scale bar, 500 μm. F, Section through the entorhinal cortex ipsilateral to the side of intrahippocampal BoNT/A injection. Labeling for cleaved SNAP-25 (red) is evident in superficial layers. Neuronal counterstaining is in green. Note that other areas of the cortex are not stained, ruling out passive spread. Dorsal is up and lateral is to the left. Scale bar, 100 μm.