Fig. 1.

Focal applications of glutamate to adjacent nonoverlapping regions along the axon of L7. Low-power Nomarski contrast images of an SN–L7 culture after 4 d. The axon of L7 emerges from the cell body and extends toward the top of each micrograph. The axon of the SN (left of motor axon) emerges from the cell body and extends toward the motor axon. The location of regenerated SN neurites and varicosities contacting L7’s axon is determined with epifluorescent microscopy after intracellular dye injections (see Figs. 3, 4, 5). Micropipettes for pressure ejection (positioned at left of motor axon) and rapid suction (right of motor axon) of glutamate are placed opposite a given region at three locations along L7’s axon (distal locations inA and B and most proximal location inC). The width of the glutamate stream is controlled by the placement of the electrodes and the strength of the vacuum. In these examples, the stream width is ∼10 μm. Scale bar, 40 μm.