Topographic changes in high-affinity glutamate uptake in the cat red nucleus, substantia nigra, thalamus, and caudate nucleus after lesions of sensorimotor cortical areas

The distribution of presumed glutamatergic projections from sensorimotor cortical areas to the red nucleus (RN), the substantia nigra (SN), the ventrolateral thalamic complex, and the caudate nucleus (CN) was investigated in the cat. For this purpose, the changes in the sodium-dependent high-affinity glutamate uptake (HAGU) rate were measured in homogenates of tissue microdissected from various parts of these subcortical structures after chronic surgical ablation of sensorimotor cortical areas. After 8 to 10 days survival, significant reductions in HAGU activity were noted in the structures studied on the side ipsilateral to the operated cortex. Within each structure, various quantitative or qualitative changes were observed. Higher decreases in HAGU activity were found in the caudal part of the RN, the ventrolateral thalamic nucleus, and the dorsolateral part of the CN than in the other parts of these structures. The lateral part of the SN showed a large decrease in HAGU rate and its medial part a small but significant increase. Referring to the anatomic data concerning the organization of cortical projections from sensorimotor areas to the structures studied, it was shown that our results support the view that glutamate could act as a neurotransmitter along various corticosubcortical pathways.