Apical dendrite

Pyramidal neurons are the principal long-projecting cells of the cerebral cortex and hippocampus. They are so named because of the characteristic large apical dendrite, giving them a pyramidal shape. 

It appears that the voltage waves recorded in the EEG represent the summation of synaptic potentials in the apical dendrites of pyramidal cells in the cortex. These cells generate sufficient extracellular current for it to reach, and be recorded from, the cranium and scalp. Although these waves originate from the cortex rather than the SCN, the distinctive REM and non-REM phases of sleep still remain after destruction of the SCN but they then occur randomly over the 24-h cycle. This is a further indication that the SCN is at least partly responsible for setting the overall circadian rhythm of the sleep cycle. 

Chronic corticosterone treatment or repeated restraint stress promotes atrophy of apical dendrites of CA3 pyramidal neurons. 

Margarinos A, McEwen BS, Flugge G, Fuchs E (1996) Chronic psychosocial stress causes apical dendritic atrophy of hippocampal CA3 pyramidal neurons in subordinate tree shrews. J Neimosci 16 3534-3540... 

Watanabe Y, Gould E, McEwen BS (1992a) Stress induces atrophy of apical dendrites of hippocampal CA3 pyramidal neurons. Brain Res 588 341-345 Weeber E, Atkins CM, Selcher JC, Varga AW, Mirnikjoo B, Paylor R, Leitges M, Sweatt JD (2000) A role for the p isoform of protein kinase C in fear conditioning. J Neurosci 20 5906-5914... 

Watanabe, Y., Gould, E., McEwen, B.S. (1992a). Stress induces atrophy of apical dendrites of hippocampal CA3 pyramidal neurons. Brain Res, 588, 341-5. 

In vertebrates, most of the olfactory neurons of the nasal epithelium protrude from the apical dendritic knob a variety of cilia into the protective mucus layer, thus enlarging the sensory surface area of the cells. A subpopulation of sensory neurons in the main olfactory epithelium and all of the neurons in the vomeronasal organ (VNO) are structurally different their apical region of the dendrite extends in an array of microvilli. 

Jakab RL, Goldman-Rakic PS. 5-Hydroxytryptamine2A serotonin receptors in the primate cerebral cortex possible site of action of hallucinogenic and antipsychotic drags in pyramidal cell apical dendrites. Proc Natl Acad Sci USA 1998 95 735-740. 

Aghajanian GK, Marek GJ. Serotonin induces excitatory postsynaptic potentials in apical dendrites of neocortical pyramidal cells. Neuropharmacology 1997 36 589-599. 

Fig. 1. Serotonin 5-HT2A receptor immunolabeling in rat frontal cortex. (A) Labeling of 5-HT2A receptors in the frontal cortex shown at low magnification. Note dense labeling of layer V pyramidal neurons and their apical dendrites. Scale bar 100 pm. (B) Layer V pyramidal neurons shown at higher magnification. Scale bar 20 pm. Adapted from ref. 22.

In AD neurons, there are three main types of neurofibrillary lesions (NFLs) according to their intracellular localization neurofibrillary tangles (NFTs) inside the cell body and apical dendrites, and neuropil threads (NThs) in distal dendrites and dysrophic neurites, associated with senile plaques. Morphologically, three major subtypes of NFTs can be distinguished, corresponding to different evolutionary stages of these lesions. 

Pyramidal cell— named on the basis of the cell body s shape. It is one of the two major neuronal types found in the cerebral cortex. It has a large apical dendrite, which extends vertically from the top of the pyramid, and basal dendrites, which come off horizontally at the base of the pyramid. The axon also typically extends from the base. 

A.C. Kwan, D.A. Dombeck, W.W. Webb, Proximal apical dendrites have uniform polarity microtubules. PNAS 105(32), 11370-11375 (2008)... 

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