| We tested the following hypotheses in cultured sympathetic neurons: (1) L-type Ca2+ channels are predominantly on the soma and proximal neurites pre- and post-neuritotomy; (2) blocking L-type channels at the time of injury inhibits regeneration and alters the NGF receptor distribution. A fluorescent dihydropyridine antagonist (1.5 μM) was used, and neuritotomy was with a motorized rubber impactor. L-type channels are ubiquitously distributed pre- and post-neuritotomy. Although cell bodies remained viable, regeneration was severely inhibited by the antagonist when administered 15–20 min. pre-neuritotomy, in the presence or absence of NGF (p < 0.0001). Regeneration was minimally inhibited by the antagonist when administered 5 min. post-neuritotomy (p < 0.05) and not inhibited when administered 2 or 24 hr. post-neuritotomy (p > 0.05). Blocking L-type channels did not alter the NGF receptor distribution pre- or post-neuritotomy. Since blocking L-type channels inhibited neurite regeneration without affecting cell viability pre- or post-neuritotomy, these channels have a specific role in regeneration. |
