title: Glutamate, aspartate and co-localization with calbindin in the medial thalamus. An immunohistochemical study in the rat.
abstract: Topographical and quantitative features of medial thalamic neurons in which aspartate (ASP) or glutamate (GLU) might act as neurotransmitters were investigated in the rat. The calcium-binding protein calbindin D-28k (CB) was exploited as a marker of neuronal subsets, thus allowing us to study also the relationships between the CB-containing neurons and those immunoreactive to excitatory amino acids. Double immunocytochemistry of ASP and CB or GLU and CB was performed in 40-microm-thick sections. The three markers were distributed in the thalamic midline, mediodorsal, anterior intralaminar and ventromedial nuclei, with regional variations. ASP-immunoreactive neurons appeared more numerous than the GLU-immunoreactive ones throughout these structures; ASP-CB or GLU-CB double-immunostained neurons were evident. ASP-, GLU- and CB-immunoreactive cells were then quantitatively evaluated in 5-microm-thick consecutive sections. Interindividual variations and different anti-ASP and anti-GLU antibodies did not result in significant differences. ASP and GLU were not co-localized. Single ASP- or GLU-immunoreactive neurons accounted for 60% of the total number of immunostained cells, and single ASP-immunopositive cells represented more than half of these neurons. Among the CB-immunoreactive cells (40% of the total), half were double immunostained; the proportion of double CB-ASP-immunopositive neurons was sevenfold higher than that of the CB-GLU-immunoreactive ones. These results indicate that ASP may act as excitatory neurotransmitter in a relatively high proportion of medial thalamic neurons, in which ASP frequently coexists with CB. Approximately 50% of the CB-immunoreactive cells did not contain either ASP or GLU, suggesting that some medial thalamic neurons may utilize a different neurotransmitter.
authors.affiliation: Dipartimento di Neurofisiologia, Istituto Nazionale Neurologico C. Besta, Milano, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Frassoni
authors.forename: R
authors.initials: R
authors.lastname: Spreafico
authors.forename: M
authors.initials: M
authors.lastname: Bentivoglio
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D064026:Calbindins; D018698:Glutamic Acid / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D013787:Thalamic Nuclei / Q000378:metabolism*
chemical_list: D064026:Calbindins; D009419:Nerve Tissue Proteins; D064030:S100 Calcium Binding Protein G; D001224:Aspartic Acid; D018698:Glutamic Acid