Oligodendrocyte Differentiation and Myelination Is Potentiated via GABA Receptor Activation.

Differentiation of oligodendrocyte precursor cells (OPCs) into mature oligodendrocytes (OLs) is a key event for axonal myelination in the central nervous system (CNS). Several growth factors and neurotransmitters like GABA are postulated as important regulators of that process, and different protein kinases may also participate in OL differentiation and myelination. However, the molecular mechanisms underlying the regulation of myelination by neurotransmitters are only partially known. In the present study, we provide evidence showing that GABA receptors (GABARs) play an important role in OL differentiation. First, we observed that OPCs and OLs synthesize GABA and expressed GABAR and transporters, both in vitro and in vivo and, in contrast to GABARs, the subunits GABAR and GABAR are expressed in OLs over time. Then, we found that exogenous GABA increases the number of myelin segments and MBP expression in DRG-OPC cocultures, indicating that GABA regulates myelination when OLs are in contact with axons. Notably, in purified rat OPC cultures, chronic treatment with GABA and baclofen, specific GABAR agonist, accelerates OPC differentiation by enhancing the processes branching and myelin protein expression, effects that are reverted in presence of GABAR specific antagonist CGP55845. Exposure of OPCs to baclofen promotes the Src-phosphorylation, and the baclofen-induced maturation is attenuated in presence of the Src-family kinases inhibitor PP2. None of these effects are mediated by the GABAR agonist muscimol. Together, these results highlight the relevance of the GABAergic system in OL differentiation, and indicate that this functional role is mediated through GABAR involving the participation of Src-family kinases. This article is part of a Special Issue entitled: Honoring Ricardo Miledi - outstanding neuroscientist of XX-XXI centuries.