Glutamate, aspartate and co-localization with calbindin in the medial thalamus. An immunohistochemical study in the rat

C. Frassoni, R. Spreafico, M. Bentivoglio

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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-μm-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-μm-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.

Original languageEnglish
Pages (from-to)95-104
Number of pages10
JournalExperimental Brain Research
Issue number1
Publication statusPublished - 1997


  • Calcium-binding proteins
  • Excitatory amino acids
  • Rat
  • Thalamic nuclei

ASJC Scopus subject areas

  • Neuroscience(all)


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