[Varying intensity and staining of neurons in the cat visual cortex during histochemical detection of horseradish peroxidase].

We have investigated the staining of different types of neurons after horseradish peroxidase injection in the cat striate cortex. The intensity of staining was classified as dark, intermediate, or light. Cells with different staining intensities were found in all cortical layers and at different distances from the injection site. According to the shape of their somata and the organisation of their dendritic trees, the labelled cells were identified as pyramidal, small pyramidal, non pyramidal and modified pyramidal (inverted and fusiform). The ratio of dark:light:intermediate cells within all identified morphological types was 2:1:1, except for the modified pyramidal neurons (1:1:1). Revealed peculiarity of modified pyramidal cells may serve as additional characteristic of this morphological type cells. Thus the intensity of staining depends not only on the physical uptake and transportation of enzyme but also on the organisation of axonal terminals and neuron location in the functional structure of the cortex.