The Journal of Neuroscience, July 15, 1998, 18(14):5344-5353
Identification of the Dopamine D3 Receptor in Oligodendrocyte
Precursors: Potential Role in Regulating Differentiation and
Myelin Formation
Ernesto R.
Bongarzone1,
Sherrel G.
Howard1, 2,
Vilma
Schonmann1, and
Anthony T.
Campagnoni1
1 Mental Retardation Research Center and Brain Research
Institute and 2 Molecular and Medical Pharmacology, School
of Medicine, University of California at Los Angeles, Los Angeles,
California 90024
Expression of the dopamine D3 receptor (D3r) was found in primary
mixed glial cultures from newborn brain and in the corpus callosum
in vivo during the peak of myelination. Expression of the D3r mRNA, but not D2r mRNA, was detected as early as 5 d
in vitro (DIV) by RT-PCR. Immunoblot studies revealed
D3r protein was also expressed in the cultures. Double
immunofluorescence analysis for the D3r and for surface markers of
specific stages of oligodendrocyte development indicated that D3r
expression occurred in precursors and in immature oligodendrocytes but
not in mature oligodendrocytes (i.e., A2B5+
007
01
and
A2B5+ 007+
01
cells but not A2B5
007+ 01+ cells). Confocal
microscopic analysis indicated that D3r was associated with cell bodies
and cell membranes but not with the processes emanating from cell
somas. Immunohistochemistry of brain sections revealed the presence of
D3r in some oligodendrocytes located mainly within the genu and radiato
of the corpus callosum during the active period of myelination.
Treatment of cultures with 20 µM quinpirole led to
decreased numbers of O1+ oligodendrocytes possessing
myelin-like membranes as well as an increase in the number of
precursors in 14 DIV cultures. This effect was prevented by the
dopamine antagonist haloperidol. These results show that the D3r
expression is not restricted to neurons but it is also expressed in
differentiating oligodendrocytes before terminal maturation. It also
suggests that dopamine or some other D3r ligand may play a role in
oligodendrocyte differentiation and/or the formation of myelin by
mature oligodendrocytes.
Key words:
myelination; dopamine receptors; brain
development; cell lineage; oligodendroglia; neurotransmitters
Copyright © 1998 Society for Neuroscience 0270-6474/98/18145344-10$05.00/0