Human Foetal Neuroblasts Exhibit BK Channel-Dependent Membrane Voltage Oscillations upon Depolarization

Immature neurobalsts might present peculiar electrical activities before developing standard neuronal-like excitability. We previously described electrophysiological properties of primary neuroblast cultures isolated from the nucleus basalis of Meynert (hfNBMNs) of 12-week human foetuses, which possess the machinery for acetylcholine (ACh) synthesis, degradation and transport, functional muscarinic and nicotinic ACh receptors and tetrodotoxin- (TTX-) sensitive Na⁺ and K⁺ currents. Here we report an unexpected electrical activity, encountered by serendipity in neuroblasts while seeking for standard, neuronal-like, action potentials, consisting in high-frequency (70 Hz on average), periodic-like oscillations of membrane voltage evoked by cell depolarization. This activity was sensitive to intracellular thapsigargin or 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), as well as to extracellular tetraethylammonioum, Ba²⁺ or Iberiotoxin, thus indicating the involvement of big conductance Ca²⁺-activated K⁺ (BK) channel family. Our data demonstrate that hfNBMNs present recurrent, BK-dependent, high-frequency voltage waves which may reflect an immature excitability pattern involved in early neuronal maturation or cholinergic network integration within foetal basal forebrain, whose lack might lead to neurodevelopmental disorders as those associated to premature birth. Further research is needed to deepen its pharmacological characterization and eventual occurrence in an integrated brain tissue.