Fig. 4. Delayed nerve regeneration in nerves of GFAP-null mice measured by neurophysiology and motor neuron retrograde labeling with GFP-conjugated cholera toxin subunit B. (A) The total number of labeled motor neurons in the lumbar enlargement 48 hours after injection of fluorescent cholera toxin subunit B in the gastrocnemius is significantly reduced in GFAP-null mice compared with control mice. (B) Distal cMAP recordered in nerves of GFAP-null mice always showed amplitudes of half-values compared with controls, whereas NCVs did not show significant differences; ^*P<0.05. Bar, 50 µm.