Kanold PO, Shatz CJ (2002) Developmental regulation of GABA Receptor subunits requires subplate neurons. Neuroscience 2002 Abstracts 530.11. Society for Neuroscience, Orlando, FL.
Summary: Subplate neurons (SP) are required for formation and patterning of thalamocortical connections. In visual cortex, SP ablation before the onset of the critical period, but when LGN axons are already in layer 4, prevents segregation into ocular dominance columns (ODCs) and emergence of functional orientation columns. Recent studies have linked ODC plasticity with maturation of inhibitory circuitry, which requires the appropriate expression and developmental regulation of GABA receptor subunits. We therefore wondered if SP ablation alters GABA-R subunit expression. Focal injections of kainic acid or immunotoxin were made into cat SP between P7-P10, just prior to the onset of ODC formation. 3 weeks later, in situ hybridization revealed that expression of several subunits of the GABA-A receptor was reduced in the ablated region, especially in layer 4. Other genes involved in synaptic function such as Homer and mGluR subunits also decreased in expression. These changes in gene expression suggest that the efficacy of inhibition in layer 4 is reduced. A reduction in postsynaptic GABA receptors is consistent with previously observed increases in BDNF and GAD expression after SP ablation. These observations imply that SP neurons are essential for the maturation of cortical inhibition, which in turn may be needed for the formation of ODCs and for the functional maturation of thalamocortical connections.
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