Journal of Neuroscience, Vol 9, 4158-4168, Copyright © 1989 by Society for Neuroscience
Ultrastructural localization of molecular subtypes of immunoreactive neural cell adhesion molecule (NCAM) in the adult rodent striatum
M DiFiglia, P Marshall, J Covault and M Yamamoto
Department of Neurology, Massachusetts General Hospital, Boston 02114.
Neural cell adhesion molecule (NCAM) is a plasma membrane glycoprotein that
is thought to mediate adhesion between neuronal elements and play an
important role in neural development. Although NCAM has been found in the
adult brain, as well as the developing brain, little is known about its
function or ultrastructural distribution. A monoclonal antibody which was
directed against embryonic (E15-E17) mouse brain and identified 180 and 140
kDa molecular weight forms of NCAM was used to examine the
immunohistochemical localization of NCAM in the rodent striatum. Light
microscopic results in the adult mouse and rat showed that most NCAM180,140
immunoreactivity was localized to the relatively small population of medium
and large-sized aspiny interneurons of the caudate nucleus and to the
majority of neurons in the globus pallidus. Ultrastructural analysis
revealed that reaction product in aspiny somata was present in discrete,
closely spaced patches of cytoplasm along the inner face of the plasma
membrane and was also prominent in somatic protrusions which were
frequently apposed to synapsing axons. Distal aspiny and pallidal dendrites
containing NCAM180,140 received numerous synaptic inputs. Within caudate
neuropil NCAM180,140 was also present in spines with thin necks and small
spine heads which were postsynaptic to unlabeled axon terminals and in
preterminal (unmyelinated) axons and terminal boutons that issued from
myelinated bundles and formed asymmetric synapses with unlabeled dendritic
spines. This study provides the first evidence in adult brain that
NCAM180,140 varies in extent and location within neurons. The heterogeneous
distribution of NCAM180,140 in neurons of the basal ganglia may be related
to a number of functions such as maintaining or modulating the density and
distribution of synaptic inputs and the formation of new contacts on
dendritic spines.