Ionotropic glutamate‐receptor gene expression in hypothalamus: Localization of AMPA, kainate, and NMDA receptor RNA with in situ hybridization

Abstract

In situ hybridization and Northern blots were used to study the ionotropic subtypes of the glutamate receptor in the rat hypothalamus. Widespread expression of AMPA, kainate, and NMDA receptor RNA was found in the hypothalamus with the transcripts the same size and number as found in other regions of the brain. Most of the glutamate-receptor subunits studied were expressed in greater amounts in hippocampus than in hypothalamus; GluR5, on the other hand, showed a greater expression in hypothalamus than in hippocampus. On the basis of Northern blot analysis, all regions of the brain examined, including hypothalamus, cerebral cortex, cerebellum, olfactory bulb, and hippocampus, expressed all eight of the subunits studied. Each subunit showed different relative expressions in the different regions. In the hypothalamus, GluR1 and GluR2 were among the most widely expressed of the non-NMDA ionotropic receptors. Other AMPA-preferring receptors, GluR3 and -R4, were also found, but to a lesser extent. Scattered cells expressed the kainate-preferring receptors GluR5, -R6, and -R7. The NMDA receptor NMDAR1 was detected throughout the hypothalamus. In many regions of the hypothalamus, only scattered cells showed detectable expression of the glutamate-receptor mRNA as detected by autoradiographic silver grains over neurons; unlabeled cells were mixed among labeled cells. Every region of the hypothalamus had several different glutamate receptors. The expression of many different types of ionotropic glutamate receptors throughout the hypothalamus suggests that multiple modes of ion channel regulation by glutamate probably operate here and provides further support for the importance of the excitatory transmitter glutamate in hypothalamic regulation.

Pre‐ and postsynaptic actions of opioid and orphan opioid agonists in the rat arcuate nucleus and ventromedial hypothalamus in vitro

“…Presynaptic actions of opioids in the arcuate nucleus and VMH Arcuate nucleus neurones express both ionotropic (van den Pol et al 1994) and metabotropic glutamate receptors (Ghosh et al 1997). Excitatory neurotransmission mediated by AMPAÏKA glutamate receptors has been suggested to mediate the majority of fast excitatory synaptic transmission in the medial basal hypothalamus (van den Pol et al 1990).…”

Neurotransmitter Regulation of Cellular Activation and Neuropeptide Gene Expression in the Paraventricular Nucleus of the Hypothalamus

“…This result was unexpected, because the PVH is known to express a variety of (mainly ionotropic) glutamate receptors (van den Pol et al, 1994;Aubry et al, 1996;Herman et al, 2000;Eyigor et al, 2001) and to receive a substantial glutamatergic innervation (van den Pol et al, 1990;van den pol, 1991). The role of glutamate in the regulation of PVH mechanisms is unsettled, and its effects on parvocellular neurosecretory neurons have not been thoroughly characterized (Oliver et al, 1996;Herman and Cullinan, 1997).…”

Kainate Receptor-Induced Retrograde Inhibition of Glutamatergic Transmission in Vasopressin Neurons

“…These receptors are also present postsynaptically (Huettner, 2003;Lerma, 2003) in which they were shown to participate to the synaptic response (Castillo et al, 1997;Vignes and Collingridge, 1997). Evidences from in situ hybridization studies in the SON indicate an absence of GluK2, GluK3, and GluK4 mRNA, low levels of GluK1 mRNA in some neurons, and high levels of GluK5 in all neurons (van den Pol et al, 1994;Eyigor et al, 2001). In the magnocellular subdivision of the PVN, GluK1 mRNA labeling matches the distribution of VP neurons (Herman et al, 2000).…”