The Journal of Neuroscience, September 1, 2001, 21(17):6874-6888
Dendritic Arborizations of the Rat Substantia Nigra Pars
Reticulata Neurons: Spatial Organization and Relation to the Lamellar
Compartmentation of Striato-Nigral Projections
P.
Mailly2,
S.
Charpier1,
S.
Mahon1,
A.
Menetrey1,
A. M.
Thierry1,
J.
Glowinski1, and
J. M.
Deniau1
1 Institut National de la Santé et de la
Recherche Médicale U 114, Chaire de Neuropharmacologie,
Collège de France, 75231 Paris Cedex 05, France, and
2 Neurobiologie des Processus Adaptatifs-Neurobiologie des
Signaux Intercellulaires, Centre National de la Recherche
Scientifique, Université Pierre et Marie Curie, 75005 Paris
France
The cerebral cortex provides a major source of inputs to the basal
ganglia. As has been well documented, the topography of corticostriatal
projections subdivides the striatum into a mosaic of functionally
distinct sectors. How information flow from these striatal sectors
remains segregated or not within basal ganglia output nuclei has to be established.
Electrophysiologically identified neurons of the rat substantia nigra
pars reticulata were labeled by juxtacellular injection of Neurobiotin,
and the spatial organization of their dendritic arborizations was
analyzed in relation to the projection fields of individual striatal
sectors. Thirty-nine nigral neurons located in the projection territory
of the distinct striatal sensorimotor sectors were reconstructed. The
data show that the dendritic arborizations of nigral neurons conform to
the geometry of striato-nigral projections. Like striatal projections,
the arborizations formed a series of curved laminas enveloping a
dorsolaterally located core. Although dendritic fields of the neurons
lying in the laminae were flat, those located in the core were
spherical or cylindrical, thereby conforming to the shape of the
striatal projection fields. This remarkable alignment between the
dendritic arborizations of nigral neurons and the projection fields
from individual striatal districts supports the concept of a parallel
architecture of the striato-nigral circuits. However, pars reticulata
neurons usually extend part of their dendrites within adjacent striatal
projection fields, thereby ensuring a continuum between channels. The
extension of the dendritic arborizations within the striatal projection
fields suggests that nigral neurons integrate the information that is relevant for the completion of the specific motor behavior they control.
Key words:
substantia nigra pars reticulata; dendritic fields; juxtacellular injection; functional compartmentation of the basal
ganglia; three-dimensional reconstruction; striato-nigral
projections
Copyright © 2001 Society for Neuroscience 0270-6474/01/21176874-15$05.00/0