The Journal of Neuroscience, June 1, 1998, 18(11):4201-4215
Distinctive Morphological Features of a Subset of Cortical
Neurons Grown in the Presence of Basal Forebrain Neurons In
Vitro
Dun H.
Ha1,
Richard T.
Robertson1, and
John H.
Weiss1, 2, 3
Departments of 1 Anatomy and Neurobiology,
2 Neurology, and 3 Psychobiology, University of
California, Irvine, Irvine, California 92697-4292
Basal forebrain cholinergic neurons (BFCNs) provide the major
subcortical source of cholinergic input to cerebral cortex and play an
important role in regulating cortical activity. The present study
examined the ability of BFCNs to influence neocortical neuronal growth
by examining effects of the presence of BFCNs on certain cortical
neurons grown under the controlled conditions of dissociated cell
culture. Initial experiments demonstrated distinctive morphological features of a population of neurons (labeled with SMI-32, a monoclonal antibody to nonphosphorylated neurofilament proteins that labels pyramidal neurons in vivo) in cocultures containing
basal forebrain (BF) and cortical cells. These neurons (large neurons
immunoreactive for SMI-32 [SMI-32(+) neurons]) were characterized as
having extensive axons, greater soma size, and more dendritic growth
than did most SMI-32(+) neurons in the cultures. Staining for SMI-32 in
cocultures in which the cortical neurons were labeled with a
fluorescent marker before adding the BF cells indicated that virtually
all large SMI-32(+) neurons were of cortical origin. Eliminating BFCNs with the selective cholinergic immunotoxin 192 IgG-saporin resulted in
a >80% decrease in the number of large SMI-32(+) neurons, although causing little damage to other cells in the treated cultures; this
suggests that survival or maintenance of large SMI-32(+) neurons may
depend on ongoing trophic support from BFCNs. Thus, present findings
suggest that BFCNs may provide powerful growth- and/or
survival-enhancing signals to a subset of cortical neurons.
Key words:
ChAT; cholinergic; SMI-32; 192 IgG-saporin; pyramidal; culture; Alzheimer's disease; trophic interaction
Copyright © 1998 Society for Neuroscience 0270-6474/98/18114201-15$05.00/0