Jeffery G; Sharp C; Malitschek B; Salt TE; Kuhn R; Knopfel T; (1996) Cellular
localisation of metabotropic glutamate receptors in the mammalian optic nerve: A
mechanism for axon-glia communication. Brain Research, 741: 75-81.
It has been proposed that neurotransmitter signalling can occur between axons and glia in the
mammalian optic nerve in the absence of synaptic specialisations, and that this may be glutamate
mediated. Here, the cellular distribution of five metabotropic glutamate receptors (mGluR's la, Ib,
Ic, 2/3 and 5) have been assessed in the rat optic pathway using specific antibodies. Positive
immunoreactivity is found for mGluR2/3 and 5. Both are found in axons, although only mGluR5
is present in the majority of these. Strong immunoreactivity for mGluR2/3 is found in cells in the
optic pathway and thalamus. The cellular morphology and distribution is consistent with their
being astrocytes. Examination of brain sections stained for mGluR2/3 is consistent with this
notion, with many cells having end-feet processes terminating on blood vessels or the pial surface.
The axonal immunoreactivity could represent the presence of these receptors on axons, but it is
more probable that the receptor protein synthesised in the ganglion cell soma is being
transported to the cell terminal in sufficient concentration to be revealed by
immunohistochemistry. The reason for the axon- astrocyte signalling is unclear, and may be
associated with metabolic coupling, In development, communication between axons and glia
mediates a range of functions including pathway selection and myelination. It is probable that in
the adult this form of signalling underpins a range of functions that have yet to be described.
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Last Updated January 27, 1997.