Ligand‐gated channels in early mesencephalic neuronal precursors: immunocytochemical and electrophysiological analysis

Abstract

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.

Effects of GABA and GABA receptor inhibition on differentiation of mesencephalic precursors into dopaminergic neurons in vitro

“…In the present and other studies both GABA A and GABA B receptors were located in DA cells (Kim et al, 1997;Wirtsshafter and Sheppard, 2001;Schlesinger et al, 2004) as well as in glial cells and other cell populations such as serotonergic cells (Wirtsshafter and Sheppard, 2001), which have been shown to regulate generation of DA cells from proliferating neurospheres of mesencephalic precursors. We have previously shown that elimination of serotonergic cells or inhibition of serotonin synthesis induces a marked increase in generation of DA cells from proliferating neurospheres of mesencephalic precursors (Rodriguez-Pallares et al, 2003), and it has been reported that GABA A receptor antagonists significantly reduced the survival of serotonergic neurons in primary cultures from rat brainstem (Liu et al, 1997).…”

“…During embryonic development, GABA appears long before the onset of inhibitory synaptogenesis, and GABA-mediated signaling is thought to be involved in the regulation of nearly all key developmental stages ranging from cell proliferation, differentiation, and migration to circuit refinement (Varju et al, 2001;Owens and Kriegstein, 2002a,b). Furthermore, GABA receptors are present in neural progenitors from the very beginning of neuronal determination, and both GABA B and particularly GABA A receptors have been involved in development regulation (Wang et al, 2003;Jelitai et al, 2004;Schlesinger et al, 2004). However, the possible effects of GABA on generation of DA neurons from proliferating neurospheres of mesencephalic precursors have not been studied.…”

Developmental regulation and lateralization of GABA receptors in the rat hippocampus

“…In detailed studies have indicated that GABA receptors depolarize immature neurons, and play an excitatory effect (Ben‐Ari, 2002; Cherubini et al, 1990; LoTurco et al, 1995; Meier et al, 2003; Schlesinger et al, 2004). Therefore, GABA is the major excitatory neurotransmitter before the maturation of glutamatergic synapses (Ben‐Ari et al, 2007; Khazipov et al, 2001; Tyzio et al, 1999).…”

WITHDRAWN: Developmental regulation and lateralization of GABA receptors in the rat hippocampus

“…In detailed studies have indicated that GABA receptors depolarize immature neurons, and play an excitatory effect (Ben-Ari, 2002;Cherubini et al, 1990;LoTurco et al, 1995;Meier et al, 2003;Schlesinger et al, 2004). Therefore, GABA is the major excitatory neurotransmitter before the maturation of glutamatergic synapses (Ben-Ari et al, 2007;Khazipov et al, 2001;Tyzio et al, 1999).…”