Type Glutamate Receptor Subunits Research Articles

Ischaemia does not alter the editing status at the Q/R site of glutamate receptor-A, -B, -5 and -6 subunit mRNA.

The editing status of mRNA at the Q/R site of the AMPA/kainate type glutamate receptor (GluR) subunits A, B, 5 and 6 modulates the ion selectivity of glutamate receptor operated ion channels. We hypothesized that a long-lasting dysfunction of this editing process after an ischeamic insult may be involved in the process of delayed neuronal cell death. In order to test this hypothesis, the editing status of the GluRs was determined in the hippocampus of rats up to 24 h after 10 min of global ischaemia. No statistical significant differences were found in the hippocampus of animals after ischaemia compared with controls. It is concluded that delayed neuronal cell death is not mediated by a less selective or less efficient mRNA editing process of the different glutamate receptor subunits in the hippocampus.

NMDA (NMDAR1) and AMPA-type (GluR2/3) receptor subunits are expressed in the inner ear.

Using receptor subunit-specific antibodies, the cellular localization of NMDA and AMPA type glutamate receptor subunits was studied within the rodent (rat, guinea pig) and non-human primate (monkey) inner ear. In the spiral and vestibular ganglion, almost all cells were immunoreactive for the NMDAR1 subunit and the AMPA type receptor subunit GluR2/3. This indicates that both NMDA and non-NMDA type glutamate receptors may be co-distributed in the primary afferent neuronal components, and are possibly involved in neurotransmission in the primary auditory and vestibular systems. This study also indicated the possible localizations of glutamate receptors in the nonneuronal cells in the inner ear, suggesting that some nonneuronal cells may also have the ability to mediate glutamate signalling.

Characteristic localization of non-NMDA type glutamate receptor subunits in the rat pituitary gland

While the involvement of the glutamate receptors in the hypothalamo-hypophyseal system has been clarified at the hypothalamic level, the existence of glutamate receptors in the pituitary gland has remained obscure. We investigated the localization of the glutamate receptors, the non-NMDA type receptor subunits (GluR1-4) in particular, by immunocytochemistry using specific antibodies. The antibodies specific to GluR1, GluR2/3 and GluR4 exhibited the characteristic localization of the receptor molecules in each lobe of the pituitary gland. GluR1- and GluR2/3-positive cells were identified in the anterior and intermediate lobe, and intense terminals of GluR4 and weak terminals of GluR2/3 were observed in the posterior lobe. Such immunoreactivity appeared to be at the axonal terminal of the neurosecretory magnocellular cells. This was confirmed by in situ hybridization histochemistry using specific oligodeoxynucleotide probes and by immunocytochemistry in the neurosecretory magnocellular neurons. The GluR4 mRNA-positive signal and GluR4 immunoreactivity were abundantly observed in magnocells of paraventricular and supraoptic nuclei. In addition to the positive fibers, some pituicytes in the posterior lobe exhibited GluR2/3 immunoreactivity. This suggests that pituicytes have non-NMDA type glutamate receptors. Thus, present study suggests that some anterior pituitary cells and pituicytes in the neural lobe are regulated by the glutamate.