Morphological features of layer V pyramidal neurons in the cat parietal cortex: An intracellular HRP study

Abstract

Layer V pyramidal neurons in the cat parietal cortex (areas 5 and 7) were investigated with intracellular HRP staining. Antidromic responses were recorded intracellularly as well as extracellularly with pontine stimulation under Nembutal anesthesia. The relationship between the latency of antidromic responses and the morphology of HRP-stained neurons was analyzed. A total of 65 neurons were stained with HRP, and sixteen of these neurons were activated antidromically with pontine stimulation. Two distinct groups of layer V pyramidal neurons were detected morphologically by intracellular HRP staining; i.e., one (F type) consisted of neurons with relatively large somata (58.4 +/- 8.1 micron X 24.5 +/- 5.1 micron, N = 11) and aspiny or sparsely spinous apical dendrites, and the other (S type) consisted of neurons with smaller somata (44.6 +/- 7.6 micron X 19.3 +/- 3.9 micron, N = 22) and richly spinous apical dendrites. These two groups showed different electrophysiological properties; i.e., the former responded antidromically to pontine stimulation at a latency shorter than 1.5 ms (namely, with a conduction velocity faster than 18 m/second) and the latter responded at a latency longer than 1.5 ms. The two neuronal types in the parietal cortex corresponded respectively to fast and slow pyramidal tract neurons (PTNs) investigated in the sensorimotor cortex. Although their morphological features were almost similar to those of PTNs, the branching pattern of apical dendrites of the F-type pyramidal neuron seemed to be different from that of fast PTNs. In the parietal cortex, apical dendrites of F-type neurons showed rather frequent branching in layer I. This was similar to the pattern of branching in slow PTNs. Such a characteristic branching pattern suggested that, in the cat parietal cortex, layer V pyramidal neurons of both types are adapted to receive cerebellar inputs through the ventroanterior (VA) thalamic nucleus to the superficial cortical layers.

Comparative neocortical neuromorphology in felids: African lion, African leopard, and cheetah

“…As has been noted previously (Johnson et al, 2016), such differences in the basilar array may indicate a lower cellpacking density in larger felids than in the domestic cat (Jardim-Messeder et al, 2017). Similar to the Siberian tiger and clouded leopard (Johnson et al, 2016), and the domestic cat (Ghosh et al, 1988;Hübener et al, 1990;Yamamoto, Samejima, & Oka, 1987), most apical dendrites in the present study singularly ascended vertically from the soma, with some bifurcating narrowly in a V-shaped pattern a slight distance from the soma. Thus, the present findings suggest that felid neocortical architecture generally illustrates a mostly vertically-oriented type of columnar information processing similar to that documented in rodents and primates (DeFelipe, Hendry, Hashikawa, Molinari, & Jones, 1990;Innocenti & Vercelli, 2010;Mountcastle, 1997;Valverde & Facal-Valverde, 1986), with mini-columns similar to those documented in the giraffe, platypus, and human (DeFelipe, Alonso-Nanclares, & Arellano, 2002).…”

Laminar and connectional organization of a multisensory cortex

“…As in the other regions of ferret neocortex, the PPr exhibited six distinct layers that were evident when processed with SMI‐32, as depicted in Figure 1A. Here, layer 1 appeared mostly devoid of label; layer 2 had short stained fibers that ran mostly perpendicular to the pial surface; layer 3 contained darkly stained pyramidal neurons; layer 4 was extremely thin and mostly devoid of neurons and label; layer 5 contained darkly stained pyramidal neurons, but sublamination was not discernible (see also Yamamoto et al,1987); and layer 6 was mostly devoid of label and ended where the white matter began. In tissue reacted for NeuN, shown in Figure 1B, the same pattern of lamination was generally evident, although the NueN labeling in layer 4 was now evident as sparse patches of small neuronal somata.…”

Mammals

“…Interestingly, , studying the prenatal development of the cerebral cortex in Golgi material of a variety of mammals, including the hamster, mouse, rat, cat and humans, arrived at a similar conclusion. Pyramidal neurons showing these morphological differences have also been found in lamina V of the somatosensory (Yamamoto et al 1987a), parietal (Yamamoto et al 1987b) and visual (Hiibener et al 1990) cortices of the cat. During further development, a certain proportion of these neurons elongate their apical dendrite and retain their original connection with layer I, thus becoming real or typical pyramidal neurons, but others lose their initial anchorage to layer I and in Marin-Padilla's opinion become transformed into various types of local circuit neurons.…”