Journal of Neuroscience, Vol 8, 79-89, Copyright © 1988 by Society for Neuroscience
Selective staining of a subset of GABAergic neurons in cat visual cortex by monoclonal antibody VC1.1
JR Naegele, Y Arimatsu, P Schwartz and CJ Barnstable
Laboratory of Neurobiology, Rockefeller University, New York, New York 10021.
VC1.1 is a monoclonal antibody generated against cat area 17, which
selectively outlines subsets of cortical neurons (Arimatsu et al., 1987).
This study was conducted to determine the ultrastructural distribution of
the VC1.1 antigen and to identify the particular subclasses of cortical
neurons that were labeled. In the light microscope, VC1.1 delineated the
surfaces of neurons located mainly in layer IV but also in other layers.
The staining surrounded neuronal cell bodies and dendrites in a periodic or
meshwork pattern but did not label axons. VC1.1-labeled neurons were
morphologically heterogeneous and included multipolar, bipolar, and
bitufted classes. In the electron microscope, VC1.1 immunoreactivity
surrounded presynaptic membranes of terminal boutons and intersynaptic
sections of postsynaptic membranes, but was not present within terminal
boutons or synaptic clefts. Both asymmetric and symmetric synapses were
immunoreactive. Labeling was also observed intracellularly on
VC1.1-outlined neurons, associated with perisynaptic portions of plasma
membranes. Tract-tracing methods were used in conjunction with
immunocytochemistry to determine whether VC1.1 identified projection
neurons, local circuit neurons, or a combination of both types. Layer V and
VI corticogeniculate and corticotectal projection neurons were retrogradely
labeled with rhodamine fluorescent latex microspheres. In a large sample of
retrogradely labeled neurons, none were VC1.1-positive, suggesting that
VC1.1 stained a population of local circuit neurons. Additional
immunocytochemical double-labeling studies with an antiserum to GABA and
VC1.1, revealed that VC1.1-positive neurons were immunoreactive to GABA.
These were a major subset of the GABAergic neurons in area 17 and tended to
have medium to large cell bodies. It is concluded that VC1.1 identifies a
new, immunologically distinct subset of GABAergic neurons in area 17. The
restricted distribution of this antigen on perisynaptic portions of
GABA-containing cells and surrounding terminal boutons onto these cells
suggests that this antigen may play an important role in inhibitory
cortical circuits.