Immunogold Detection of L-glutamate and D-serine in Small Synaptic-Like Microvesicles in Adult Hippocampal Astrocytes

Glutamate and the N-methyl-D-aspartate receptor ligand D-serine are putative gliotransmitters. Here, we show by immunogold cytochemistry of the adult hippocampus that glutamate and D-serine accumulate in synaptic-like microvesicles (SLMVs) in the perisynaptic processes of astrocytes. The estimated concentration of fixed glutamate in the astrocytic SLMVs is comparable to that in synaptic vesicles of excitatory nerve terminals (∼45 and ∼55 mM, respectively), whereas the D-serine level is about 6 mM. The vesicles are organized in small spaced clusters located near the astrocytic plasma membrane. Endoplasmic reticulum is regularly found in close vicinity to SLMVs, suggesting that astrocytes contain functional nanodomains, where a local Ca2+ increase can trigger release of glutamate and/or D-serin

Immunogold Detection of L-glutamate and D-serine in Small Synaptic-Like Microvesicles in Adult Hippocampal Astrocytes.

Glutamate and the N-methyl-D-aspartate receptor ligand D-serine are putative gliotransmitters. Here, we show by immunogold cytochemistry of the adult hippocampus that glutamate and D-serine accumulate in synaptic-like microvesicles (SLMVs) in the perisynaptic processes of astrocytes. The estimated concentration of fixed glutamate in the astrocytic SLMVs is comparable to that in synaptic vesicles of excitatory nerve terminals (∼45 and ∼55 mM, respectively), whereas the D-serine level is about 6 mM. The vesicles are organized in small spaced clusters located near the astrocytic plasma membrane. Endoplasmic reticulum is regularly found in close vicinity to SLMVs, suggesting that astrocytes contain functional nanodomains, where a local Ca(2+) increase can trigger release of glutamate and/or D-serine

Changes in glutathione in the hippocampus of rats injected with kainate: Depletion in neurons and upregulation in glia

Experimental Brain Research1324510-516EXBR

GABA and glutamate-like immunoreactivity in processes presynaptic to afferents from hair plates on the proximal joints of the locust leg

Hair plate afferents from coxal group 1 on the meso- and prothoracic legs of the locust were backfilled with cobalt salts or HRP for light and electron microscopy. The distribution of the terminal branches of the afferents is described from wholemount preparations and from 150 μm thick slices through the ganglion. Identified branches from the slices were sectioned for electron microscopy and examined for the presence of input and output synapses. Both were found in close proximity on small-diameter varicose branches in all parts of the arborization. Immunocytochemistry using antibodies against GABA and glutamate was used to try to identify putative transmitters in processes presynaptic to the afferents. Ninety-three percent of processes presynaptic to the hair plate afferents were clearly immunoreactive for GABA and only 7% appeared unlabelled. Most neuronal processes in the vicinity of afferent terminals were also immunoreactive for GABA, but a small number of glutamate-immunoreactive processes were found in intimate contact with afferents and one of these was demonstrated to be presynaptic. Processes postsynaptic to the afferents were of small diameter (mean=0.28 μm) and were not found to be immunoreactive for GABA

The expression of vesicular glutamate transporters VGLUT1 and VGLUT2 in neurochemically defined axonal populations in the rat spinal cord with emphasis on the dorsal horn

<p>Two vesicular glutamate transporters, VGLUT1 and VGLUT2, have recently been identified, and it has been reported that they are expressed by largely nonoverlapping populations of glutamatergic neurons in the brain. We have used immunocytochemistry with antibodies against both transporters, together with markers for various populations of spinal neurons, in an attempt to identify glutamatergic interneurons in the dorsal horn of the mid-lumbar spinal cord of the rat. The great majority (94–100%) of nonprimary axonal boutons that contained somatostatin, substance P or neurotensin, as well as 85% of those that contained enkephalin, were VGLUT2-immunoreactive, which suggests that most dorsal horn neurons that synthesize these peptides are glutamatergic. In support of this, we found that most somatostatin- and enkephalin-containing boutons (including somatostatin-immunoreactive boutons that lacked calcitonin gene-related peptide and were therefore probably derived from local interneurons) formed synapses at which AMPA receptors were present.</p> <p>We also investigated VGLUT expression in central terminals of primary afferents. Myelinated afferents were identified with cholera toxin B subunit; most of those in lamina I were VGLUT2-immunoreactive, whereas all those in deeper laminae were VGLUT1-immunoreactive, and some (in laminae III–VI) appeared to contain both transporters. However, peptidergic primary afferents that contained substance P or somatostatin (most of which are unmyelinated), as well as nonpeptidergic C fibres (identified with <i>Bandeiraea simplicifolia</i> isolectin B4) showed low levels of VGLUT2-immunoreactivity, or were not immunoreactive with either VGLUT antibody. As all primary afferents are thought to be glutamatergic, this raises the possibility that unmyelinated afferents, most of which are nociceptors, express a different vesicular glutamate transporter.</p&gt