In vivo labelling of L-type Ca 2+ channels by fluorescent dihydropyridine: correlation between ontogenesis of the channels and the acquisition of neural competence in ectoderm cells from Pleurodeles waltl embryos

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The ability of the ectodermal cells to be induced and to differentiate toward neural tissue, called neural competence, is acquired shortly before gastrulation and lost during late gastrula stages in Pleurodeles walfl embryos. We have examined ectodermal cells' neural competence in relation to the evolution of the density of L-type calcium channels using the fluorescent labelled dihydropyridine probe (STBodipy-DHP). We find that the appearance of dihydropyridine sensitive calcium channels (L-type Ca 2+ channels) is correlated with the acquisition of neural competence by the ectoderm cells. The highest density of these channels is reached when competence of the ectoderm is optimal. Conversely, the decrease of L-type Ca 2+ channel density occurs simultaneously with the normal loss of competence. In addition, we show that these channels are functional since stimulation by S(−)-Bay K 8644 triggered an increase in [Ca 2+] i revealed by fluorescence measurements using FIuo-3. This increase in [Ca 2+] i is a function of the L-type Ca 2+ channels' density. We propose that the molecular basis of the gain and loss of neural competence is linked to the presence of L-type Ca 2+ channels in ectodermal cell membranes of Pleurodeles waltl embryos.