highly significantP < 0.001
However, the average neurite extension of unperfused growth cones dropped from 12.8 + 1.2 t~m (SEM) during the l-h control period to -3.1 + 1.8 #m (SEM) during the 1-hperfusion period, which was highly significant (P < 0.001, two-tall paired t test).