Division of Labor in the Dendrite

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Science  18 Aug 2000:
Vol. 289, Issue 5482, pp. 1109-1111
DOI: 10.1126/science.289.5482.1109e

An important part of brain growth and maturation in mammals occurs during the first weeks of postnatal development. This can be seen in the extensive change in size and dendritic arborization of neocortical neurons during this period, but large parts of this process are incompletely understood. Zhu used morphological and electrophysiological methods to study the maturation of layer V pyramidal neurons in the rat.

The apical dendrite of these neurons lengthened and thickened, displaying more than a fivefold increase in size at postnatal day 2. This change was accompanied by a switch from high to very low electrical input resistance of dendrite and cell body. Consequently, the apical tuft of the dendrite and the soma became more and more electrotonically isolated from each other.

During the same period the ion channel composition in the dendritic plasma membrane underwent a change from mainly sodium-dependent to the complex calcium- and sodium-dependent mature pattern. As a result, large suprathreshold synaptic inputs in the distal part of the dendritic tree of adult layer V pyramidal neurons can be nonlinearly amplified and can subsequently trigger axonal action potentials.

These findings may have important consequences for information processing on the cellular and network level during the development and maturation of the brain. They also may be valuable for the interpretation and comparison of data from laboratories that use preparations from different developmental stages. — PDS

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