Ultrastructural morphology of projections from the medial geniculate nucleus and its adjacent region to the basal ganglia.
The efferent projections of the medial geniculate nucleus (MG) and its adjacent nuclei to the basal ganglia were studied in the rat by the antero- and retrograde tracing methods. Injections of wheat germ agglutinin conjugated to horseradish peroxidase into the caudal parts of the striatum and globus pallidus produced retrograde neuronal labeling in the medial division of the MG (MGm) and its adjacent structures including the suprageniculate, posterior intralaminar and peripeduncular nuclei, and substantia nigra pars lateralis. Injections of [3H]leucine into the MG and its surroundings resulted in anterograde labeling not only in the striatum but also in the globus pallidus. The resulting labeling was distributed exclusively in the caudal parts of these two nuclei. The electron microscopic autoradiography showed preferential radiolabeling of terminals and myelinated axons in both the globus pallidus and striatum. Labeled terminals in the pallidum mostly made symmetrical synapses on somata and major dendrites, while labeled terminals in the striatum established asymmetrical synapses on dendritic spines. These morphological differences in the synapses of the efferent systems originating from the MGm and its surrounding region suggest functional/chemical differentiations at their target sites in the basal ganglia.
Moriizumi
T
T
Department of Anatomy, University of Toronto, Ontario, Canada.
Hattori
T
T
D000818:Animals; D001345:Autoradiography; D001369:Axons / Q000378:metabolism; D001479:Basal Ganglia / Q000648:ultrastructure*; D005829:Geniculate Bodies / Q000648:ultrastructure*; D005917:Globus Pallidus / Q000648:ultrastructure; D006651:Histocytochemistry; D006735:Horseradish Peroxidase; D007930:Leucine / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D009434:Neural Pathways / Q000648:ultrastructure*; D051381:Rats; D011919:Rats, Inbred Strains; D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D014909:Wheat Germ Agglutinins
D018998:Wheat Germ Agglutinin-Horseradish Peroxidase Conjugate; D014909:Wheat Germ Agglutinins; D006735:Horseradish Peroxidase; D007930:Leucine