Ligand-gated channels in early mesencephalic neuronal precursors: Immunocytochemical and electrophysiological analysis

Neuronal precursors play an important role in potential regenerative therapeutic strategies in different neurodegenerative diseases, e.g. Parkinson's disease. To understand proliferation and differentiation of these cells in vitro and in vivo, it is important to characterize functional properties of neuronal precursors in detail. The aim of the present study was to analyse the electrophysiological characteristics of ligand-gated channels of neuronal precursors prepared from the rat ventral mesencephalon (VM) of embryonic stage 12.5 during their in vitro differentiation. For the experiments we used the patch-clamp technique in combination with a system for ultrafast solution exchange and immunocytochemistry. It could be shown that functional active AMPA-type glutamate as well as GABA_A receptor channels are expressed at an early stage of neuronal development. In culture we observed excitatory as well as inhibitory postsynaptic currents (defined by their different kinetics) which correspond to the activation of AMPAergic and GABAergic receptor channels. Two populations of glutamate-activated currents could be differentiated by their different time course of desensitization whereas the time course of resensitization and deactivation was normally distributed in all cells. GABAergic currents could be blocked by bicuculline and their kinetics correspond to that of GABA_A receptor channel currents. Summarizing the results, in the present study it was shown for the first time that neuronal embryonic precursors of the rat VM express both functional AMPA-type glutamate and functional GABA_A receptor channels in vitro.