Adult Neural Stem/Progenitor Cells in the Forebrain - Drugs of Abuse: Neurological Reviews and Protocols - page 31

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Adult Neural Stem/Progenitor Cells in the Forebrain
Implications for Psychostimulant Dependence and Medication
John Q. Wang, Limin Mao, and Yuen-Sum Lau
1. Introduction
The question as to what exactly a stem cell is has remained contentious even
after nearly three decades of debate. The prevailing view is that stem cells
are cells with the capacity for unlimited or prolonged self-renewal that can
produce at least one type of highly differentiated descendant. Usually, between
the stem cell and its terminally differentiated progeny there is an intermediate
population of committed progenitors or precursors with limited proliferative
capacity and restricted differentiation potential. The term “neural stem cell”
is used loosely to describe cells that (1) are derived from the nervous system;
(2) have self-renewal capacity; and (3) can give rise to one specifi c phenotype,
or more likely multiple types, of neural cells other than themselves through
asymmetric cell division (1 , 2) . However, to date, it is not clear how primitive the
detectable population of dividing cells in the brain is. They may represent true
neural stem cells or lineage-restricted progenitor cells. Given this uncertainty,
the cautious term “neural progenitor cells” is used in this chapter to describe
dividing cells in the central nervous system (CNS).
Adult neural progenitor cells are the ones derived from the adult nervous
system. Although it has long been thought that the neural tissue in the adult
mammalian brain is entirely postmitotic, a particular surprise is the discovery
of progenitor cells in unexpected brain areas, such as the subventricular zone
(SVZ) and the hippocampal dentate gyrus, throughout adulthood (1-3) . As
compared to embryonic stem cells, which tend to proliferate at high levels and
spontaneously differentiate into all kinds of tissues, adult neural progenitor