Fig. 7. Microtubule dynamics are necessary for F-actin foci and rapid outgrowth on laminin. (A) Suppression of laminin-induced F-actin foci by nocodazole, taxol and Li⁺. Growth cones were induced to form F-actin foci by treatment with CD for 15 minutes followed by laminin for 30 minutes. Each drug was then added to cultures for 15 minutes before fixation and staining for F-actin. All three drugs significantly (P<0.00001) reduced the frequency of foci. Error bars for nocodazole and Li⁺ are too small to see. (B) Nocodazole inhibits the rapid growth of processes on laminin. Neurons were plated onto laminin or fibronectin and then exposed to 33 nM nocodazole. Recordings of the same growth cones over time were made to determine the increase in process length. Only the rapid outgrowth on laminin is substantially inhibited by this low concentration of nocodazole. (C) Dose-response curves for process outgrowth from neurons plated onto laminin or fibronectin and then exposed to CD. Cells were treated with CD for either 4 hours (fibronectin) or 2 hours (laminin) and the increase in process length measured. Error (s.e.m.) bars are too small to see. Results are representative of three separate experiments.