Table 1.

CGRP expression after depolarization required Ca²⁺ channel activity

Treatment	Blocks	Survival (%)	CGRP (%)
NB5	—	109.7 ± 8.2	7.0 ± 0.6
NB50	—	85.3 ± 2.2	26.4 ± 1.6
NB50 + tetrodotoxin	Na⁺ channel	81.4 ± 3.6	21.4 ± 1.6
NB50 + ω-conotoxin	N-type Ca²⁺ channel	86.4 ± 3.6	19.1 ± 2.3*
NB50 + verapamil	L-type Ca²⁺ channel	89.6 ± 1.6	14.4 ± 0.7**
NB50 + nifedipine	L-type Ca²⁺ channel	85.9 ± 0.6	12.0 ± 0.7***

E14.5 DRG cells were maintained in NB50 medium with 1 μm tetrodotoxin, 2.5 μm ω-conotoxin GVIA, 10 μm verapamil, or 10 μm nifedipine for 8 d before immunocytochemistry for CGRP. The percentage of CGRP-IR and surviving neurons was determined. Cell survival in all conditions was good, with 80% of neurons alive after 8 d (unpairedt test, p > 0.20). CGRP expression was inhibited by nifedipine, verapamil, and ω-conotoxin GVIA. In contrast, tetrodotoxin had no effect (unpaired t test,p = 0.14). Similar values were obtained in at least three independent experiments for each condition. Data are mean and SEM. *p < 0.05; **p < 0.01; ***p < 0.0001.