DOUBLE BOUQUET CELL AXONS IN THE HUMAN TEMPORAL NEOCORTEX - RELATIONSHIP TO BUNDLES OF MYELINATED AXONS AND COLOCALIZATION OF CALRETININ AND CALBINDIN D-28K IMMUNOREACTIVITIES

We have examined the distribution of double bouquet cell axons, immuno cytochemically stained for the calcium-binding proteins calretinin and calbindin D-28k in the human temporal neocortex, in relation to bundl es of myelinated axons (originating from pyramidal cells) and the colo calization of these calcium-binding proteins. The large number and reg ularity of distribution of double bouquet cell axons was clearly visua lized in tangential sections from cortical layers III-V. In these sect ions, we estimated that the mean number +/- standard deviation of doub le bouquet cell axons per 10,000 mu m(2) was 11.65 +/- 0.44 with a mea n diameter of 12.10 +/- 0.63 mu m and a mean center-to-center spacing of 29.8 +/- 0.91 mu m. These values are very similar to those previous ly reported in the monkey neocortex. The distribution of double bouque t cell axons was closely related to bundles of myelinated axons; there was overlapping with basically a one-to-one correspondence. Finally, double-label immunofluorescence experiments revealed that the vast maj ority of double bouquet cell axons immunoreactive for calbindin were a lso stained for calretinin. Since relatively few cell somata were doub le-labeled in the human temporal cortex, we concluded that double bouq uet cells may represent a significant subpopulation of neurons that co localize these calcium-binding proteins. (C) 1997 Elsevier Science B.V .