ABSTRACT
The neocortex is a highly specialized region in adult mammalian brain. A largely transient population of neurons localizing in the subplate has been proposed to play crucial roles in cortical development. In the first part of this thesis, I aimed to study the distribution of calcium permeable AMPA receptor (CP-AMPAR)-expressing neurons in subplate and neocortex during development and the roles played by CP-AMPARs in the death of subplate neurons. The kainate-stimulated Co2+-labeling assay was used to identify the CP-AMPAR-expressing neurons. The pretreatment of kainate coupled with the Co2+-labeling assay was used to detect the susceptibility to excitotoxicity of CP-AMPAR-expressing neurons. The widespread distribution and distinct susceptibility to excitotoxicity of CP-AMPAR-expressing neurons suggest that CP-AMPAR-expressing neurons play various important roles in the development and physiology of the rat cerebral cortex.
The neocortex and thalamus develop synchronously and link with each other through reciprocal connections, the thalamocortical and corticothalamic (CT) projections. In the second part of this thesis, the morphology of DiI-back-labeled CT neurons in perinatal rat cortices was studied. The immunoreactive signals of reelin, calbindin, GluR1, gephyrin and synaptophysin at the apical dendrites of CT neurons in perinatal rat cortices were analyzed. The results suggest that the apical dendrites of the CT neurons can form contacts with Cajal-Retzius (CR) and other cells in the marginal zone or upper cortical plate at E18. Furthermore, GABAergic and glutamatergic synapses are already formed on CT neurons in rat cortices as early as E18 when the cortical projection has just reached their thalamic targets. Thus, it is likely that the cortex and thalamus in rat brains are linked to each other by functional connections in a two-way fashion at least three days before birth.

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