Regional cortical glutamergic and aspartergic projections to the amygdala and thalamus of the rat.

Evidence continues to accumulate indicating that glutamate and aspartate act as excitatory neurotransmitters in a variety of corticofugal pathways. These two amino acids share a common high-affinity uptake system and the activity of this system is reduced when cell bodies giving rise to glutamergic or aspartergic nerve terminals are destroyed. Selective reduction of glutamate or aspartate concentration in association with decreased high-affinity uptake suggests that a given pathway utilizes the amino acid that is selectively reduced. Since various regions of the cerebral cortex vary both functionally and architectonically, it seemed a reasonable possibility that glutamergic and aspartergic neurons in different areas of the cerebral cortex might project differentially upon different subcortical nuclei. We have therefore removed various cortical regions or the olfactory bulk and determined high-affinity D-aspartate uptake and concentrations of glutamate, aspartate, and several other amino acids in the amygdala and thalamus one week later. The cortical areas which project to thalamus and amygdala are virtually exclusively ipsilateral, so that the contralateral homologous area in the same animal may be used as a control.