Abstract
In the cerebral cortex, the plant lectin Vicia villosa (VVA) selectively stains the surfaces of nonpyramidal neurons. This lectin binds specifically to alpha- and beta-linked N-acetylgalactosamine (GalNac). VVA-reactive carbohydrate is highly concentrated in layer 4 of the primary visual cortex of the cat, where it is associated exclusively with GABAergic local circuit neurons. We have studied this neuronal subset with intracellular electrophysiological recording and dye marking to identify the particular cell types expressing surface GalNac. Five different types of local circuit neurons were stained intracellularly (N = 45), but only 2 types, the columnar basket and large neurogliaform cells, were also labeled by the lectin (N = 19/45). Lectin negative types included small basket, chandelier, and large bitufted cells (26/45). Spiny stellate and pyramidal neurons were also lectin negative. Electrophysiological recordings revealed differences in the duration of action potentials in smooth versus spiny stellates but no differences between lectin-positive or -negative types. A biochemical analysis of cortical glycoproteins by SDS-PAGE and lectin blotting revealed multiple bands containing GalNac enriched in membrane fractions. These carbohydrate-containing molecules may be part of a biochemical mechanism for linking together cells with common functional properties.