CALBINDIN IMMUNOREACTIVITY IN NORMAL HUMAN TEMPORAL NEOCORTEX

Calbindin immunoreactivity in the temporal neocortex was examined in 4 subjects with no neurological, metabolic or malignant disease. The brains were obtained between 1 and 4 h after death and rapidly fixed by perfusion with 4% paraformaldehyde through the carotid arteries, cut into slabs, cryoprotected and stored at -80-degrees-C. Sections of the whole left temporal lobe obtained with a freezing microtome were processed free-floating with a well known monoclonal antibody against calbindin according to the peroxidase-antiperoxidase (PAP) method. Calbindin-immunoreactive (CaBP-ir) neurons were found to be local-circuit neurons (interneurons) mainly distributed in the upper cortical layers (layers I, II and III), and were categorized as small multipolar neurons with ascending dendrites ramifying in the molecular layer, small bitufted cells, pyramid-like cells in layer II, horizontal neurons in the molecular layer, multipolar neurons with long descending dendrites, and large double-bouquet cells, some of them exhibiting a very long dendrite with claw-shaped terminals in layer V. Less than 10% of all CaBP-ir neurons were localized in the remaining cortical layers. Pyramidal cells were only very weakly or not stained at all. In addition, CaBP-ir fibres formed a dense plexus in the molecular layer, and vertical bundles 8-10-mu-m thick and 500-600-mu-m long, separated by blank spaces 20-40 microns wide were distributed in layers III and V/VI. CaBP-ir neurons and fibres, through their contacts with pyramidal cells, may regulate contralateral and ipsilateral cortico-cortical connections, may control the vertical neuronal inhibition across different cortical layers, and may regulate the excitability of most pyramidal cells through their terminal bouquets ramifying in the molecular layer.