Developing oligodendrocytes express functional GABA<inf>B</inf>receptors that stimulate cell proliferation and migration
GABABreceptors (GABABRs) are involved in early events during neuronal development. The presence of GABABRs in developing oligodendrocytes has not been established. Using immunofluorescent co-localization, we have identified GABABR proteins in O4 marker-positive oligodendrocyte precursor cells (OPCs) in 4-day-old mouse brain periventricular white matter. In culture, OPCs, differentiated oligodendrocytes (DOs) and type 2 astrocytes (ASTs) express both the GABAB1abcdfand GABAB2subunits of the GABABR. Using semiquantitative PCR analysis with GABABR isoform-selective primers we found that the expression level of GABAB1abdwas substantially higher in OPCs or ASTs than in DOs. In contrast, the GABAB2isoform showed a similar level of expression in OPCs and DOs, and a significantly higher level in ASTs. This indicates that the expression of GABAB1and GABAB2subunits are under independent control during oligodendroglial development. Activation of GABABRs using the selective agonist baclofen demonstrated that these receptors are functionally active and negatively coupled to adenylyl cyclase. Manipulation of GABABR activity had no effect on OPC migration in a conventional agarose drop assay, whereas baclofen significantly increased OPC migration in a more sensitive transwell microchamber-based assay. Exposure of cultured OPCs to baclofen increased their proliferation, providing evidence for a functional role of GABABRs in oligodendrocyte development. The presence of GABABRs in developing oligodendrocytes provides a new mechanism for neuronal-glial interactions during development and may offer a novel target for promoting remyelination following white matter injury. © 2007 The Authors.