RT Journal Article SR Electronic T1 Depolarization Stimulates Initial Calcitonin Gene-Related Peptide Expression by Embryonic Sensory Neurons In Vitro JF The Journal of Neuroscience JO J. Neurosci. FD Society for Neuroscience SP 9294 OP 9302 DO 10.1523/JNEUROSCI.18-22-09294.1998 VO 18 IS 22 A1 Xingbin Ai A1 Sally E. MacPhedran A1 Alison K. Hall YR 1998 UL http://www.jneurosci.org/content/18/22/9294.abstract AB The neuropeptide calcitonin gene-related peptide (CGRP) is expressed by one-third of adult rat lumbar dorsal root ganglion (DRG) neurons, many of which mediate pain sensation or cause vasodilation. The factors that regulate the developmental expression of CGRP are poorly understood. Embryonic DRG neurons initially lack CGRP. When these neurons were stimulated in culture by serum or persistent 50 mm KCl application, the same percentage of CGRP-immunoreactive (CGRP-IR) neurons developed in vitroas was seen in the adult DRG in vivo. The addition of the L-type calcium channel blockers, 5 μm nifedipine or 10 μm verapamil, dramatically decreased the proportion of CGRP-IR neurons that developed, although the N-type calcium channel blocker, 2.5 μm ω-conotoxin, was less effective. By contrast, the sodium channel blocker 1 μm tetrodotoxin had no effect on CGRP expression after depolarization. Fura-2 ratiometric imaging demonstrated that mean intracellular free calcium levels increased from 70 to 135 nm with chronic depolarization, and the addition of nifedipine inhibited that increase. Only a subpopulation of neurons had elevated calcium concentrations during chronic depolarization, and they were correlated with CGRP expression. Key signal transduction pathways were tested pharmacologically for their role in CGRP expression after depolarization; the addition of the CaM kinase inhibitor KN-62 reduced the proportion of CGRP-IR neurons to basal levels. By contrast, protein kinase A and protein kinase C were not implicated in the depolarization-induced CGRP increases. These data suggest that depolarization and the subsequent Ca2+-based signal transduction mechanisms play important roles in the de novo expression of CGRP by specific embryonic DRG neurons.