Journal of Neuroscience, Vol 5, 2940-2954, Copyright © 1985 by Society for Neuroscience
Dual ultrastructural localization of two neurotransmitter-related antigens: colloidal gold-labeled neurophysin-immunoreactive supraoptic neurons receive peroxidase-labeled glutamate decarboxylase- or gold- labeled GABA-immunoreactive synapses
AN van den Pol
To study the morphological substrate for interaction between two chemically
distinct neuronal types, two double ultrastructural immunolabeling
strategies were employed. In the first, two different electron-dense
markers were used to examine simultaneously two different
neurotransmitter-related antigens in the hypothalamic supraoptic nucleus in
the same thin section. Results obtained with the first method were
confirmed with a second approach based on postembedding immunostaining of
alternate serial thin sections with different antisera. Antiserum against
glutamate decarboxylase, the enzyme responsible for the synthesis of the
inhibitory amino acid transmitter gamma-aminobutyric acid (GABA), or
antisera against GABA, was used to localize immunoreactive axons in the
hypothalamic supraoptic nucleus. With light microscopy, glutamate
decarboxylase- and GABA-immunoreactive axon terminals immunostained with
peroxidase were found arborizing throughout all areas of the nucleus;
terminal boutons were found adjacent to unlabeled somata within the
nucleus. Cells containing immunoreactive oxytocin, vasopressin, and
neurophysin were localized with peroxidase. Glutamate
decarboxylase-immunoreactive axons stained with peroxidase prior to
embedding in plastic were demonstrated to contact neurons which contained
vesicles immunostained with neurophysin antiserum by a post-embedding
immunocytochemical procedure which used immunoglobulins or protein A
adsorbed to colloidal gold as a second ultrastructural marker. Quantitative
evaluation of post- embedding staining with colloidal gold using a
neurophysin primary antiserum indicated a specific antigen localization in
neurosecretory vesicles. A critical factor in this double-labeling paradigm
was that immunological reagents used in the second series did not
cross-react with those used in the first series, regardless of the species
of origin of antisera. To provide further verification of GABAergic
synapses on neurophysin-containing neurons, alternate serial ultrathin
sections were stained with colloidal gold using antisera against either
neurophysin or GABA; boutons immunoreactive for GABA made synaptic contact
with supraoptic neurons containing neurophysin immunoreactivity. Converging
results obtained with these two procedures indicate that GABAergic axons
synapse directly on neurons containing oxytocin or vasopressin in the rat
hypothalamic supraoptic nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)