Expression and distribution of metabotropic GABA receptor subtypes GABABR1 and GABABR2 during rat neocortical development.
To understand the possible contribution of metabotropic gamma-aminobutyric acid receptors (GABABR) in cortical development, we investigated the expression pattern and the cellular and subcellular localization of the GABABR1 and GABABR2 subtypes in the rat neocortex from embryonic day 14 (E14) to adulthood. At the light microscopic level, both GABABR1 and GABABR2 were detected as early as E14. During prenatal development, both subtypes were expressed highly in the cortical plate. Using double immunofluorescence, GABABR1 colocalized with GABABR2 in neurons of the marginal zone and subplate, indicating that these proteins are coexpressed and could be forming functional GABABRs during prenatal development in vivo. In contrast, only GABABR1 but not GABABR2 was detected in the tangentially migratory cells in the lower intermediate zone. During postnatal development, immunoreactivity for GABABR1 and GABABR2 was distributed mainly in pyramidal cells. Discrete GABABR1-immunopositive cell bodies of interneurons were present throughout the neocortex. In addition, GABABR1 but not GABABR2 was found in identified Cajal-Retzius cells in layer I. At the electron microscopic level, immunoreactivity for GABABR1 and GABABR2 was found in dendritic spines and dendritic shafts at extrasynaptic and perisynaptic sites throughout postnatal development. We further demonstrated the presynaptic localization of GABABR1 and GABABR2, as well as the association of the receptors with asymmetrical synaptic junctions. These results indicate potentially important roles for the GABABRs in the regulation of migratory processes during corticogenesis and in the modulation of synaptic transmission during early development of cortical circuitry.
López-Bendito
G
G
Department of Human Anatomy and Genetics, University of Oxford, OX1 QX, UK. guillermina.lopez-bendito@anat.ox.ac.uk
Shigemoto
R
R
Kulik
A
A
Paulsen
O
O
Fairén
A
A
Luján
R
R
D000818:Animals; D000831:Animals, Newborn; D064026:Calbindins; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002451:Cell Compartmentation / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002465:Cell Movement / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005333:Fetus; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D007150:Immunohistochemistry; D019579:Neocortex / Q000196:embryology* / Q000254:growth & development* / Q000378:metabolism; D009419:Nerve Tissue Proteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism; D009474:Neurons / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D018079:Receptors, GABA / Q000378:metabolism*; D018080:Receptors, GABA-B / Q000378:metabolism*; D000091042:Reelin Protein; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D012697:Serine Endopeptidases; D012794:Sialic Acids / Q000378:metabolism; D013570:Synaptic Membranes / Q000378:metabolism / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D064026:Calbindins; D015816:Cell Adhesion Molecules, Neuronal; D016326:Extracellular Matrix Proteins; C116566:Gabbr2 protein, rat; D009419:Nerve Tissue Proteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; D018079:Receptors, GABA; D018080:Receptors, GABA-B; D000091042:Reelin Protein; D064030:S100 Calcium Binding Protein G; D012794:Sialic Acids; C103469:polysialyl neural cell adhesion molecule; D005680:gamma-Aminobutyric Acid; D012697:Serine Endopeptidases