Layers I and VI of the visual cortex in the rabbit. A correlated Golgi and immunocytochemical study of somatostatin and vasoactive intestinal peptide containing neurons.

Immunocytochemical and Golgi staining techniques were used to correlate the morphology of neurons in layers I and VI of the rabbit's visual cortex. Antisera against somatostatine (SOM) and vasoactive intestinal peptide (VIP) were employed in the immunocytochemical investigation. In layer I, SOM-positive cells were multipolar and situated in the lower part of the layer. Some had long horizontal axons like those of the Cajal-Retzius cells when observed by the Golgi method. Most VIP-positive cells were bipolar and some had axons throughout this layer. In layer VI, SOM-positive cells were of multipolar, bitufted, or pyramidal-like morphology. Frequently, they presented a thicker and more prominent dendrite with various collaterals and axons with ascending, horizontal and sometimes descending courses. Cells with recurrent axon were occasionally observed. Either the dendrite or the axonal characteristics are similar to some Golgi-impregnated non-pyramidal cells of our material, including the inverted pyramidal neurons. In this study, we have described peptidergic cells in these layers and correlate them with Golgi impregnated neurons and with those described in the literature.