Journal of Neuroscience, Vol 12, 116-131, Copyright © 1992 by Society for Neuroscience
Partial glycinergic denervation induces transient changes in the distribution of a glycine receptor-associated protein in a central neuron
T Seitanidou, MA Nicola, A Triller and H Korn
INSERM U261, Departement des Biotechnologies, Institut Pasteur, Paris, France.
The effect of partial glycinergic denervation on the cellular distribution
of the 93 kDa peripheral polypeptide associated with the glycine receptor
was studied at the level of the teleost Mauthner cell, an identified neuron
of the goldfish brain (Carassius auratus). Previous studies using
monoclonal antibodies raised against purified glycine receptors and
immunoperoxidase staining have shown that these proteins are localized in
clusters on the entire surface of this neuron. Specifically, the 93 kDa
polypeptide was situated only on the cytoplasmic side of the postsynaptic
membrane facing active zones. Unilateral electrolytic lesions of the
vestibular complex caused the degeneration of some glycinergic afferents to
this neuron. When the first signs of this response appeared, 3 d after the
surgery, there was also a change in the ultrastructural distribution of the
93 kDa polypeptide in the deafferented cell. The synaptic protein apposed
to degenerating axons did not spread onto adjacent extrasynaptic membranes,
and it disappeared a few hours after the disruption of its presynaptic
element. At the same time, a cytoplasmic immunoreactivity appeared as
randomly distributed clusters in the deafferented Mauthner cell; these
aggregates, not seen in control preparations, were never found inside
membrane-bound organelles. In some preparations these clusters were
localized along arrays at a relatively constant distance from the plasma
membrane. The intracellular immunoreaction product was found in the soma
and the initial part of the dendrites, gradually decreasing in number and
intensity toward the extremities of these processes. At later postoperative
stages, 10-15 d after surgery, the 93 kDa immunoreactivity remained only at
postsynaptic membranes facing intact terminals. Similar alterations
following denervation were observed in reticular neurons, at the level at
which degenerating presynaptic terminals were also detected. In contrast,
continuous 3-d blockade of synaptic transmission by strychnine, an
antagonist of the glycine receptor, had no effect on either the
distribution of the surface receptor clusters, or the 93 kDa peripheral
protein linked to these receptors. Taken together, our results suggest that
the ultrastructural distribution of the glycine receptor complex is
regulated by "trophic" factors rather than by transmitter-evoked synaptic
activity.