CA1 pyramidal neuron

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The CA1 Pyramidal Neuron is a neuron in the CA1 region of the mammalian hippocampus.

Key: Region: D, dendrite; S, soma (cell body); AH, axon hillock-initial segment of the axon; A, axon; T, axon terminal. Type of dendrite: e, equivalent cylinder (for single dendrites and multipolar trees); a, apical; b, basal; o, oblique. Level of dendrite: (p) proximal, (m) middle, and (d) distal with respect to the cell body. For further explanations, see canonical representations. Graphic from: GM Shepherd, Synaptic Organization of the Brain, New York: Oxford University Press 1978.

Basic information

The CA1 Pyramidal Neuron is found in the CA1 region of the mammalian hippocampus in the medial temporal lobe. "CA" refers to cornu Ammon, latin for Ammon's horn (so named for the shape of the hippocampus). The neurons in the CA1 region provide a significant output pathway from the hippocampus, which plays an important role in long-term memory and spatially related tasks. CA1 pyramidal neurons, in particular, are thought to be critical to object differentiation in long-term memory. Their relationship with Schaffer collaterals in the CA3 region of the hippocampus leads to long-term potentiation (LTP) which is a critical component of information storage.

Neuronal Type: Projection neuron


Anatomy

  • The cell body of the CA1 pyramidal neuron is located amidst a thick set of dendritic branches and one projecting axon. The dendrites bind together in a thick band called the stratum radiatum.
  • The axons of pyramidal cells in the CA1 region project mostly to the entorhinal cortex layer V and to the subiculum.
  • CA1 contains approximately 250,000 pyramidal neurons.


Molecular profile

  • Neurotransmitter: Glutamate, which is the primary excitatory neurotransmitter in the mammalian brain.


Physiology

Synaptic Connections

Modified drawing of the neural circuitry of the rodent hippocampus. By Santiago Ramón y Cajal. Histologie du Systeme Nerveux de l'Homme et des Vertebretes, Vols. 1 and 2. A. Maloine. Paris. 1911. This image was created using Gimp, starting from a file already uploaded on Wikepedia. Source: Wikipedia [1]

Synaptic Inputs

  • CA1 pyramidal cells receive inputs from the pyramidal cells in the CA3 region called Schaffer collaterals, and also from the superficial entorhinal cortex and the nucleus reuniens of the thalamus. Unlike other regions of the hippocampus, the CA1 region does not contain many recurrent pathways. Input is received both from dendrites and backpropagation in the axon.

Synaptic Outputs

  • CA1 pyramidal cells project to the entorhinal cortex layer V and also to the subiculum, which is at the end of the hippocampus.

Behavior

  • The relationship between CA1 pyramidal neurons and Schaffer collateral cells have been implicated in LTP (the strengthening of a synapse due to recent activity). Malinow et al. (1989) found that brief, high-frequency stimulation of the Schaffer collaterals causes LTP in the CA1-Schaffer collateral synapse. LTP is input specific, the effects of LTP on one synapse do not occur in other, inactive synapses. This is key for information storage. In LTP, CA1 pyramidal neurons reach their maximum output, and thus for further information to be encoded in these neurons, long-term depression (LTD) needs to occur along other synapses.
  • Changes in dendritic density are thought to be associated with neuronal damage inflicted by ischemia (restricted blood supply) (Ruan YW, Lei Z, Fan Y, Zou B, Xu ZC (2008)).
  • Although controversy lingers, Golding, Nace L., William L. Kath, and Nelson Spruston (2001), as well as others, have argued that backpropagation occurs in the dendrites of the cell, which may be critical to understanding their plasticity.

Links

References

  1. Amaral, DG (1978). "A Golgi study of cell types in the hilar region of the hippocampus in the rat". J. Comp. Neurol. 15: 851-914.
  2. Amaral, D; Lavenex P (2006). "Ch 3. Hippocampal Neuroanatomy", in Andersen P, Morris R, Amaral D, Bliss T, O'Keefe J: The Hippocampus Book. Oxford University Press. ISBN 9780195100273.
  3. Andersen, P; Bliss TVP, Skrede KK (1971). "Lamellar organization of hippocampal excitatory pathways". Exp. Brain Res. 13: 222-238. doi:10.1007/BF00234087.
  4. Andersen, P; Soleng AF, Raastad M (2000). "The hippocampal lamella hypothesis revisited". Brain Res. 886: 165-171. PMID 11119694.
  5. Duvernoy, H (2005). The human hippocampus, 3rd ed. Springer Verlag.
  6. Golding, Nace L., William L. Kath, and Nelson Spruston. Dichotomy of Action-Potential Backpropagation in CA1 Pyramidal Neuron Dendrites. J. Neurophysiol. 86: 2998-3010, 2001.
  7. Lorente De Nó, R (1934). "Studies on the structure of the cerebral cortex. Continuation of the study of the ammonic system". J. Psychol. Neurol. 46: 113-177.
  8. Malinow, R., H. Schulman, and R.W. Tsien (1989). Inhibition of postsynaptic PKC or CaMKII blocks induction but not expression of LTP. Science 245: 862-866.
  9. Purves, Dale, Augustine, George J., Fitzpatrick, David, Hall, William C., LaMantia, Anthony-Samuel, McNamara, James O., and Williams, Mark S. (2004). Neuroscience. 3rd ed. Massachusetts: Sinauer Associates, Inc.
  10. Shepherd, GM (1998). The Synaptic Organization of the Brain. Oxford University Press.
  11. Ruan YW, Lei Z, Fan Y, Zou B, Xu ZC (2008). “Diversity and fluctuation of spine morphology in CA1 pyramidal neurons after transient global ischemia.” Neurosci Res J, Aug. 15. [2]