A pyramidal cell (or pyramidal neuron, or projection neuron) is a multipolar neuron located in the hippocampus and cerebral cortex. These cells have a triangularly shaped soma, or cell body, a single apical dendrite extending towards the pial surface, multiple basal dendrites, and a single axon. Pyramidal neurons compose approximately 80% of the neurons of the cortex, and release glutamate as their neurotransmitter, making them the major excitatory component of the cortex.

In the primary motor cortex, layer V pyramidal cells are extremely large. These cells are called Betz cells. Their cell bodies can be as large as 100 micrometers in humans. Typical human pyramidal cell bodies range from 10 to 50 micrometers. Also, any pyramidal cell that faces the opposite direction of a Betz cell (i.e. its longest dendrite faces the opposite direction of all of the other Betz cells) is known as a Martinotti cell.

Pyramidal cells are tall and conical, triangular in tissue sections. Their apex points toward the brain surface and has a thick dendrite with many branches, and small, knobby dendritic spines. The base gives rise to horizontally oriented dendrites, and an axon that passes into the white matter. Pyramidal cells are the output neurons of the cerebrum. They transmit signals to other parts of the CNS. Their axons have collaterals that synapse with other neurons in the cortex or in deeper regions of the brain.

CaMK (calcium/calmodulin-dependent protein kinase II, CaMKII)

• a marker for Pyramidal cells. PMID: 16374802
• a useful marker for pyramidal neurons in ultrastructural studies of ABL synaptology and that the activity of pyramidal neurons in the ABL is tightly controlled by a high density of GABAergic terminals that target all postsynaptic domains of pyramidal neurons. PMID: 11932937

Emx1

• a mouse homologue of Drosophila empty spiracles, is specifically expressed in the developing telencephalic cortex, and can be reliably used as a marker of the pyramidal cell lineage. PMID: 11709490
• a marker for pyramidal neurons. PMID: 11698592

GluR2/3

• in the rat basolateral amygdala GluR2/3-ir is found primarily in pyramidal neurons whereas GluR1-ir is found mainly in non-pyramidal neurons that contain PV or CB. PMID: 8733298

MAP2 (microtubule-associated protein 2)

• Expressed on dendrites of pyramidal neurons in the cerebral cortex and hippocampus, is a pyramidal cell dendrites marker. PMID: 15982644, PMID: 16409548, PMID: 11796132
• a cytoskeletal phosphoprotein that regulates the dynamic assembly characteristics of microtubules and appears to provide scaffolding for organelle distribution into the dendrites and for the localization of signal transduction apparatus in dendrites, particularly near spines. PMID: 12834896
• exhibited a somatodendritic pattern of localization in cells of the hippocampus. PMID: 11057027

MATH-2

• marker of hippocampal pyramidal cells or dentate granule cells. PMID: 12379251   

mGluR1/mGluR5

• mGluR5 is the major postsynaptic mGluR expressed in CA1 pyramidal neurons. PMID: 15882947
• mGluR1 and mGluR5 play distinct roles in the regulation of the excitability of hippocampal CA1 pyramidal neurons. PMID: 11487615

Neurogranin/RC3

• the pyramidal cell marker. PMID: 16957090, PMID: 15115741
• expressed in virtually all pyramidal neurons and spiny stellate neurons of neocortical areas 4, 3b, 1, 2, 5, 7, and SII, but not in the majority of cortical interneurons. PMID: 16304627
• a protein that binds calmodulin and serves as a substrate for protein kinase C, is highly expressed in dendritic spines of hippocampal pyramidal cells, implicating this protein in long-term potentiation and in learning and memory processes. PMID: 11811671

PSD-95/SAP90

• distributed in the dendrites of pyramidal neurons of the hippocampus and neocortex. PMID: 10521598

RPTPalpha

• a novel member of the functional class of genes that control radial neuronal migration, is a key mediator of neuronal migration and synaptic plasticity. PMID: 12912911

RPTPgamma (receptor protein tyrosine phosphatase gamma)

• a marker for pyramidal cells and sensory neurons in the nervous system and is not necessary for normal development. PMID: 16782895

RPTPzeta/beta

• a receptor-like protein tyrosine phosphatase expressed as a chondroitin sulfate proteoglycan, is localized mainly at the postsynaptic membrane of pyramidal neurons in adult cerebral cortex and hippocampus. PMID: 15982644, PMID: 9655611

SCIP

• the hippocampal pyramidal cell marker. PMID: 12379251
• expressed at high levels in the cerebral cortex, specifically in layer 5 pyramidal neurons that form subcortical axonal connections, and is also expressed at high levels in the neurons of cortical layer 2/3, during their migration and differentiation within the cortical plate. PMID: 7905511

SMI-32

• a pyramidal cell (neuron) marker. PMID: 14724256, PMID: 15941378, PMID: 14724256, PMID: 7517410
• an antibody directed against a nonphosphorylated neurofilament protein that labels pyramidal cells and a subpopulation of pyramidal neurons in the human and monkey neocortex. PMID: 10473757, PMID: 2496154
• a monoclonal antibody that recognizes a non-phosphorylated epitope on the medium- and high-molecular weight subunits of neurofilament proteins. As in carnivores and primates, SMI-32 immunoreactivity in the hamster neocortex was present in cell bodies, proximal dendrites and axons of some medium and large pyramidal neurons located in cortical layers III, V and VI. A small population of labeled multipolar cells was also found in layer IV. PMID: 15820621
• Immunoreactivity with the SMI-32 antibody was largely confined to a single sublayer of layer V pyramidal neurons in discrete subregions of the somatosensory, visual, and auditory cortices, as well as a large field in the frontal cortex (Fr1). Surprisingly, SMI-32 neurons were absent from the motor cortex. PMID: 15236232
• labels primarily the cell body and dendrites of pyramidal neurons in cortical layers III, V, and VI. PMID: 11745654

Tbr1

• an early pyramidal neuron marker. PMID: 15634788

Zfp312

• selectively expressed by layer V and VI subcortical projection pyramidal neurons and their progenitor cells, and plays a critical role in layer- and neuronal subtype-specific patterning of cortical axonal projections and dendritic morphologies. PMID: 16314561

Other Pyramidal Cell Markers

• Pax6, Tbr2/Eomes, NeuroD, and Tbr1 are expressed sequentially during the neurogenesis of pyramidal-projection neurons. PMID: 16621079