Regulation of somatostatin gene expression by veratridine-induced depolarization in cultured fetal cerebrocortical cells.

The stimulatory effect of veratridine (VTD) depolarization upon somatostatin mRNA (SS mRNA) levels in primary cultures of fetal cerebrocortical cells was analyzed. Depolarizing stimuli, such as 100 microM VTD exposure for 30 min, elicited an increase in immunoreactive somatostatin (IR-SS) release to the media without affecting SS mRNA levels. These levels increased when exposure to depolarization stimuli was prolonged up to 3 or more hours. At this time, veratridine acted as a secretagogue, stimulating somatostatin secretion, but was also effective in stimulating somatostatin mRNA levels. These changes were blunted by the Na+ channel blockade tetrodotoxin (TTX), and partially abolished by the Ca2+ channel antagonist, verapamil (VPM). To study whether VTD may affect mRNA stability we determine the rate of disappearance of SS mRNA after inhibition of transcription by actinomycin D and demonstrated that VTD stimulation did not stabilize the SS mRNA. These results indicate that the induction of SS mRNA expression by VTD involves the modulation of Ca2+ and Na+ channels. The time course study confirmed that the VTD-induced SS mRNA accumulation is time-dependent, and requires a prolonged exposure to stimulate SS gene expression. VTD stimulation does not modify the SS mRNA rate of degradation.