AMPA-selective glutamate receptor subunits in the rat hippocampus during aging

The levels of mRNAs for the subunits of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-selective glutamate receptors (GluR-1, -2, -3, -4) in the rat hippocampus during aging were measured by Northern blotting. The distribution of these receptors was also examined at the protein level by immunoblotting using antibodies to GluR-1 and to an epitope common to GluR-2 and GluR-3 (denoted GluR-2/3). During aging a significant decrease of GluR-1 protein, but no change in the corresponding mRNA level, was observed. No differences in the level of GluR-2/3 protein and GluR-2, -3, and -4 mRNAs at the various ages examined (4, 12, and 24 months) were detected. Our results show that AMPA receptors are only slightly influenced by the aging process in the rat hippocampus. The slight decrease in GluR-1 protein content, not accompanied by a parallel decrease in the GluR-1 mRNA level, might be explained by a decreased translational efficiency or an increased protein degradation of the GluR-1 subunit. © 1995 Wiley-Liss, Inc.     

Non-NMDA glutamate receptor binding in canine brain after global cerebral ischemia and reperfusion

We employed a canine model to test the effects of global cerebral ischemia and reperfusion on binding to α-amino-3-hydroxy-5-methyl-4-isoxazole proprionate (AMPA), kainate (KA), and metabotropic glutamate receptors. Ischemia was induced by 10 min of cardiac arrest, followed by restoration of spontaneous circulation for periods of 0, 0.5, 2, 4, and 24 h. Frozen sections were prepared from parietal and temporal cortex, hippocampus, and striatum, and in vitro autoradiography was performed with one of three radioligands: [³H]AMPA, [³H]KA, or [³H]glutamate (using conditions allowing specific labeling of the metabotropic binding site). In striatum, metabotropic binding was unchanged, whereas AMPA and KA binding decreased by 20–30% at 30 min postischemia, remaining depressed through 24h. In cortex, AMPA and metabotropic binding were decreased at several timepoints after ischemia and recirculation, particularly in parietal cortex, whereas KA binding was unaffected in this tissue. Binding to hippocampal regions was largely unchanged, except for a decrease in KA binding at 2 and 4 h postischemia. These findings contrast with results from parallel studies showing increased striatal binding to NMDA receptors following ischemia. Decreased binding to non-NMDA glutamate receptors in striatum and parietal cortex may serve to protect against damage mediated through these receptors.     

Stoichiometries of AMPA receptor subunit mRNAs in rat brain fall into discrete categories

In situ hybridization was used to estimate the relative concentrations of mRNAs encoding different subunits (GluR1-4) of α-amino 3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptors in rat brain and to test the hypothesis that within-region expression profiles reflect a limited number of recurring patterns. Fractional subunit mRNA concentrations were calculated for 33 brain regions, and cluster analysis methods were applied to test for statistically meaningful groupings in the data. Four relatively homogeneous classes were identified and designated as AMPA receptor (AR) categories, numbered according to dominant subunit mRNAs. The AR-1 class (47% GluR1 mRNA) was expressed by structures near the mesodiencephalic border, including basal ganglia-related areas. The AR-2 class (57% GluR2 mRNA) was expressed in cortex and tectum. The AR-1,2 class (31% GluR1, 45% GluR2) was found in the largest number of regions, including such dissimilar cell fields as hippocampus and substantia nigra pars compacta. The AR-2,3 grouping (33% GluR2, 31% GluR3) was associated with the sensory relay and reticular thalamic nuclei. It is suggested that AR-1,2 and AR-2, the most closely related categories in clustering space, are largely telencephalic receptors with the former predominant in the subcortex and the latter in the cortex. The AR-2,3 class is associated with ascending sensory stations, whereas AR-1 appears to include several smaller categories expressed by specialized systems. If the balance of subunit mRNAs is reflected at the protein level, then the present data suggest that forebrain AMPA-type glutamate receptors can be classified into a limited number of recurring types. J. Comp. Neurol. 385:491–502, 1997. © 1997 Wiley-Liss, Inc.     

Stimulation of NMDA and AMPA glutamate receptors elicits distinct concentration dynamics of nitric oxide in rat hippocampal slices

Nitric oxide (^?NO) is an intercellular messenger implicated in memory formation and neurodegeneration in the hippocampus. Owing to its physical and chemical properties, the concentration dynamics of ^?NO is a critical issue in determining its bioactivity as a signaling molecule. Its production is closely related to glutamate N‐methyl‐D ‐aspartate (NMDA) receptors, following a rise in intracellular calcium levels. However, that dependent on α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptors remains elusive and controversial, despite reports describing a role for these receptors in other brain regions, largely because of lack of quantitative and dynamic measurements of ^?NO. Using a ^?NO‐selective microsensor inserted in the diffusional spread of ^?NO in the CA1 region of rat hippocampal slices, we measured its real‐time endogenous production, following activation of ionotropic glutamate receptors and under tissue physiological oxygen tension. Both NMDA and AMPA stimulation resulted in a concentration‐dependent ^?NO production but encompassing distinct kinetics for lag phases and slower rates of ^?NO production were observed for AMPA stimulation. Robustness of the results was achieved instrumentally and pharmacologically, by means of nitric oxide synthase (NOS) inhibitors and antagonists of NMDA (D ‐(?)‐2‐amino‐5‐phosphonopentanoic acid, AP5) and AMPA (2,3‐dioxo‐6‐nitro‐1,2,3,4‐tetrahydrobenzo[f]quinoxaline‐7‐sulfonamide, NBQX) receptors. When using glutamate as a stimulus, ^?NO production was of lower magnitude in the presence of AP5 plus NBQX than with AP5 alone, suggesting that even when NMDA receptors are inhibited Ca²⁺ rises to levels to induce a peak of ^?NO from the background. Whereas extracellular Ca²⁺ was required for the ^?NO signals, Philanthotoxin‐4,3,3 (PhTX‐4,3,3) a toxin used to target Ca²⁺‐permeable AMPA receptors, attenuated ^?NO production. These observations are interpreted on basis of a distinct coupling between the glutamate receptors and neuronal NOS. A role for Ca²⁺‐permeable AMPA receptors in the Ca²⁺ activation of neuronal NOS is suggested. © 2008 Wiley‐Liss, Inc.     

mRNA expression of AMPA receptors and AMPA receptor binding proteins in the cerebral cortex of elderly schizophrenics

L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (AMPARs) mediate the majority of the fast excitatory transmission in the CNS. To determine whether gene expression of AMPARs and/or AMPAR binding proteins, which control response/sensitivity of AMPAR-bearing neurons to glutamate, are altered in schizophrenia, mRNA expression and abundance of AMPAR subunits (GluR1-4) and several AMPAR binding proteins (SAP97, PICK1, GRIP, ABP) were measured in the dorsolateral prefrontal cortex (DLPFC) and the occipital cortex of elderly schizophrenia patients (n = 36) and matched normal controls (n = 26) by quantitative real-time PCR. The mRNA expression of GluR1, GluR4, and GRIP in the DLPFC and expression of the GluR4, GRIP, and ABP in the occipital cortex were significantly elevated in schizophrenics. GluR1 and ABP mRNA expression in the occipital cortex and GluR2, GluR3, SAP97, and PICK1 expression in either cortical area were not significantly altered. The data also demonstrated significant differences in the abundances of mRNAs encoding GluR1-4 subunits (GluR2 > GluR3 > GluR1 > GluR4) and of AMPAR binding proteins (SAP97 > PICK1 > GRIP > ABP) in both diagnostic groups. GluR2 (58-64%) and GluR3 (24-29%) were the major components of the AMPAR mRNA in both cortical areas, implying that the major AMPAR complexes in the human cortex are probably those containing GluR2 and GluR3 subunits. Small but significant differences in the amounts of GluR2, GluR3, and GRIP mRNAs were detected between the two cortical areas: more GluR3 and GRIP but less GluR2 were detected in the DLPFC than in the occipital cortex.     

Effects of nigrostriatal lesions on the levels of messenger RNAs encoding two isoforms of glutamate decarboxylase in the globus pallidus and entopeduncular nucleus of the rat.

The neurotransmitter gamma-aminobutyric acid (GABA) is present in efferent neurons of the striatum and of the pallidum, one of the main striatal target areas. Dopaminergic nigrostriatal neurons play a critical role in the regulation of GABAergic neurotransmission in the striatum. In the present study, we investigated their role in the regulation of glutamate-decarboxylase (GAD) mRNA expression in two divisions of the pallidum in rats: the globus pallidus and entopeduncular nucleus, equivalent to the external and internal pallidum, respectively, of primates. Dopaminergic neurons were lesioned by unilateral injections of 6-hydroxydopamine (6-OHDA) in the substantia nigra of adult rats. Two or 3 weeks after the lesion, frontal cryostat-cut sections of the brain were processed for in situ hybridization histochemistry with 35S-labeled RNA probes synthesized from cDNAs encoding two distinct isoforms of GAD of respective molecular weight 67,000 (GAD67) and 65,000 (GAD65). The number of labeled cells was determined, and intensity of labeling in individual cells was analyzed by computerized image analysis on emulsion radioautographs. In the globus pallidus, the number of labeled neurons and intensity of labeling per cell were increased on the side ipsilateral to the lesion as compared with control rats in sections hybridized with the GAD67 RNA probe. No changes were detected on the side contralateral to the lesion or in the levels of labeling for GAD65 mRNA. Confirming previous data, the level of labeling for GAD65 mRNA was much higher than for GAD67 mRNA in the entopeduncular nucleus of control rats. In rats with a 6-OHDA lesion, labeling for both GAD67 and GAD65 mRNAs was decreased on the side contralateral, but not ipsilateral, to the lesion, as compared with control rats. The results show that lesions of the nigrostriatal pathway in rats affect the levels of mRNAs encoding two distinct isoforms of GAD in neurons of the globus pallidus and entopeduncular nucleus differently. In addition, results in the entopeduncular nucleus further support a bilateral effect of unilateral dopaminergic lesions.     

Subunit selective decrease of AMPA and metabotropic glutamate receptor mRNA expression in rat brain by systemic administration of the NMDA receptor blocker MK-801

Glutamate mediates its effects in mammals through both ionotropic and metabotropic receptors. Antagonists of ionotropic N-methyl-d-aspartate (NMDA) glutamate receptors elicit neuroprotective and neurotropic effects that have been attributed to Ca²⁺ block through the membrane ion channel. Nonetheless, molecular and biochemical effects of NMDA receptor antagonism on other glutamate receptor subunits remain poorly understood. We investigated the effects of acute administration of the noncompetitive NMDA receptor antagonist MK-801 on the mRNA expression of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and metabotropic glutamate receptor (mGluR) subunits to determine the contribution of different glutamate receptors in response to blockade of NMDA receptor channels. In situ hybridization to rat brain sections revealed that AMPA receptor subunits GluR3 and GluR4, and mGluR3 were modestly but significantly decreased ∼10–20%, 8 h following 5 mg/kg MK-801 administration. A time course and dose response study revealed that the effect on mGluR3 was reversed by 24 h and occurred significantly at a dose range from 1 to 5 mg/kg. These results indicate that selected AMPA and mGluR subunit mRNAs respond at the RNA level to the blockade of NMDA receptors.     

Characterization of glutamate receptor interacting protein-immunopositive neurons in cerebellum and cerebral cortex of the albino rat.

Glutamate receptor interacting protein (GRIP) binds to the C-terminus of the glutamate receptor 2 (GluR2) subunit of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors in vitro and may play an important role in the synaptic organization of these receptors. To determine the distribution of GRIP in vivo, GRIP was localized immunocytochemically in cerebellum and cerebral cortex of adult Sprague-Dawley rats. In the cerebellar cortex, GRIP staining was prominent in perikarya and proximal dendrites of Purkinje cells, whereas Golgi cells were stained more weakly. Double labeling revealed that GRIP and GluR2 were colocalized in Purkinje cells but not in Golgi cells. In the cerebral cortex, GRIP-stained dendrites and somata of nonpyramidal neurons were scattered throughout cortical layers, whereas pyramidal cells were only weakly immunopositive. GRIP was especially prominent in a subset of GluR2-containing cells that also expressed a high level of GluR1. The large majority of strongly GRIP-positive cells in neocortex were immunopositive for gamma-aminobutyric acid (GABA), including the overwhelming majority of calbindin-positive cells in superficial cortical layers, most of the parvalbumin-positive cells, and half of the calretinin-positive interneurons. Staining in the neuropil became more punctate after antigen was unmasked with proteinase K. Electron microscopic localization in the cerebral cortex by postembedding immunogold showed that somatic GRIP was associated with rough endoplasmic reticulum and Golgi apparatus. GRIP was seen over the postsynaptic density of axospinous and axodendritic asymmetric synapses and at high levels in dendrites of GABA-positive neurons. The present data support a role for GRIP in anchoring AMPA receptors and suggest that GRIP trafficking may be especially active in GABAergic neurons.     

AMPA receptor antagonist LY293558 reverses preproenkephalin mRNA overexpression in the striatum of 6-OHDA-lesioned-rats treated with L-dopa

Striatal neurons that contain GABA and enkephalin and project to the external segment of the pallidum are thought to be overactive in Parkinson's disease. Furthermore, it has been shown that the appearance of L-dopa-induced dyskinesias is correlated to an increase of preproenkephalin (PPE) mRNA expression and that some antagonists of glutamate receptors can prevent and reverse L-dopa-induced dyskinesias in parkinsonian rats. The aim of this study was therefore to analyse the effect of a systemic treatment with glutamate receptor antagonists, alone or in combination with L-dopa, on the PPE mRNA level in rats with a 6-hydroxydopamine-induced unilateral lesion of the nigrostriatal pathway. In vehicle-treated animals, PPE mRNA levels were markedly increased in the striatum on the lesioned side. Sub-chronic L-dopa treatment, with bi-daily injections for 22 days, induced a further increase in PPE mRNA expression in the denervated striatum. Administration of the AMPA receptor antagonist, LY293558, partially reversed the lesion-induced and L-dopa-induced increases in PPE mRNA expression. However, although the administration of the NMDA receptor antagonist MK801 showed a tendency to decrease this L-dopa induced overexpression, it did not reach significance. This study provides evidence that glutamatergic antagonists, and particularly AMPA antagonists, tend to reverse PPE neurochemical changes at the striatal level induced by L-dopa in hemiparkinsonian rats.     

实验性癫癇大鼠海马内GDNFmRNA表达的变化

目的 :为探讨癫活动对大鼠GDNF基因表达的影响。方法 :应用同位素标记的原位杂交研究海人藻酸致后大鼠海马区GDNFmRNA表达时相的变化。结果 :正常大鼠海马未见GDNFmRNA表达 ,而癫大鼠海马神经元在致后 4h以后出现GDNFmRNA表达强烈的上调反应 ,12h达高峰 ,且各区均有表达 ,此后逐渐衰减 ,2 4h恢复正常。结论 :癫后内源性GDNFmRNA表达上调很可能是神经元对抗兴奋性损害的一种保护效应     

Localization of mRNAs encoding two forms of glutamic acid decarboxylase in the rat hippocampal formation

The mRNAs for two forms of glutamic acid decarboxylase (GAD65 and GAD67) were localized in the rat hippocampal formation by nonradioactive in situ hybridization methods with digoxigeninlabeled cRNA probes. Some neurons in all layers of the hippocampus and dentate gyrus were readily labeled for each GAD mRNA, and the patterns of labeling for GAD65 and GAD67 mRNAs were very similar. All major groups of previously described GAD-and GABA-containing neurons appeared to be labeled for each GAD mRNA. Such findings suggest that most GABA neurons in the hippocampal formation contain both GAD mRNAs. When the labeling of neurons in the hippocampal formation and cerebral cortex was compared in the same sections, the intensity of neuronal labeling for GAD67 mRNA was generally similar in the two regions. However, the intensity of labeling for GAD65 mRNA was generally stronger for many neurons in the hippocampal formation than for most neurons in the cerebral cortex. Neurons in the hilus of the dentate gyrus were particularly well labeled for GAD65. The nonradioactive labeling for the GAD mRNAs was confined to the cytoplasm of neuronal cell bodies, and this allowed a clear visualization of the relative number and location of labeled neurons. Several distinct patterns of GAD mRNA-containing neurons were observed among different regions of the hippocampal formation. In the hilus of the dentate gyrus, GAD mRNA-containing neurons were numerous in the regions deep to the granule cell layer as well as in more central parts of the hilus. Within CA3, the densities (quantities) of labeled neurons varied among the regions. In the inner or hilar segment of CA3, the density of labeled neurons was often lower than that in the outer part of CA3 where numerous labeled neurons were distributed throughout all layers. In CA1, GAD mRNA-labeled neurons were distributed in a relatively laminar pattern with the highest density in stratum pyramidale and moderate densities in stratum oriens and at the interface between strata radiatum and lacunosum-moleculare. Lower densities were found within the latter two layers. The prominent localization of the two GAD mRNAs in the hippocampal formation suggests that dual system for GABA synthesis is necessary for normal GABAergic function in this brain region. Most putative GABA neurons contain relatively high levels of GAD67 mRNA as might be expected if this GAD form is responsible for the synthesis of GABA for metabolic and baseline synaptic function. The relatively high levels of GAD65 mRNA in many hippocampal neurons, particularly those of the dentate hilus, may indicate that these neurons have a well-developed reserve system for GAD and GABA synthesis. © 1994 Wiley-Liss, Inc.     

Induction of heat shock hsp70 mRNA and HSP70 kDa protein in neurons in the ‘penumbra’ following focal cerebral ischemia in the rat

Induction of hsp70 heat shock protein (HSP70) and hsp70 mRNA was examined using adjacent sections in the same rat brain following permanent middle cerebral artery (MCA) occlusions. hsp70 mRNA was induced within 4 h of MCA occlusion and persisted for at least 24 h. Cellular resolution autoradiographs suggested that hsp70 mRNA was induced primarily in neurons in the periphery of ischemia both outside and inside of the infarction, with small amounts of hsp70 mRNA being induced in the core of the infarction. HSP70 protein was localized in neurons outside the infarction and in endothelial cells within the infarction at 24 h but not at 4 h following permanent MCA occlusions. It is proposed that the penumbra, one of the areas that can be rescued by pharmacological agents, can be defined anatomically as the volume of tissue outside the area of infarction in which HSP70 protein is expressed primarily in neurons.     

Localization of cannabinoid receptor mRNA in rat brain

Cannabinoid receptor mRNA was localized in adult rat brain by ³⁵S-tailed oligonucleotide probes and in situ hybridization histochemistry. Labelling is described as uniform or non-uniform depending on the relative intensities of individual cells expressing cannabinoid receptor mRNA within a given region or nucleus. Uniform labelling was found in the hypothalamus, thalamus, basal ganglia, cerebellum and brainstem. Non-uniform labelling that resulted from the presence of cells displaying two easily distinguishable intensities of hybridization signals was observed in several regions and nuclei in the forebrain (cerebral cortex, hippocampus, amygdala, certain olfactory structures). Olfactory-associated structures, basal ganglia, hippocampus, and cerebellar cortex displayed the heaviest amounts of labelling. Many regions that displayed cannabinoid receptor mRNA could reasonably be identified as sources for cannabinoid receptors on the basis of well documented hodologic data. Other sites that were also clearly labelled could not be assigned as logical sources of cannabinoid receptors. The localization of cannabinoid receptor mRNA indicates that sensory, motor, cognitive, limbic, and autonomic systems should all be influenced by the activation of this receptor by either exogenous cannabimimetics, including marijuana, or the yet unknown endogenous “cannabinoid” ligand. © 1993 Wiley-Liss, Inc.     

Relative concentrations and seizure-induced changes in mRNAs encoding three AMPA receptor subunits in hippocampus and cortex

In situ hybridization was used to determine 1) the relative concentrations of mRNAs encoding different subunits of the α-amino 3-hydroxy-5-methyl-4-isoxazolepropionate receptor family in select regions of rat forebrain and 2) whether limbic seizures alter the balances of the subunit mRNAs. GluR1 and GluR2 mRNA levels were about equal and were much greater than GluR3 mRNA levels in the principal neurons of each hippocampal subdivision. Probable interneurons in hippocampal molecular layers had much higher levels of GluR1 mRNA than of either GluR2 or GluR3 mRNA. Pyramidal cell layers in neo- and paleocortex had a balance of mRNAs that was significantly different from the balance in hippocampus: GluR1 mRNA and GluR3 mRNA levels were about equal and were substantially lower than those of GluR2 mRNA. Lesion-induced limbic seizures caused transient changes in mRNA levels that were differentiated with regard to subunit and brain region. All three mRNAs were decreased in the pyramidal layers of cortex, and changes in hippocampal pyramidal cells were smaller. Seizure-induced changes in granule cells of the dentate gyrus differed from all other regions examined: GluR1 mRNA was reduced to a greater degree than GluR2 mRNA, whereas GluR3 mRNA content was markedly increased. These data strongly suggest that the subunit composition of α-amino 3-hydroxy-5-methyl-4-isoxazolepropionate receptors differs significantly between areas of the cortical telencephalon. Furthermore, the data indicate that aberrant patterns of physiological activity differentially influence the expression of subunit mRNAs in a region-specific and/or cell-type-specific manner. © 1996 Wiley-Liss, Inc.     

Distribution of the AMPA2 glutamate receptor subunit in adult cat visual cortex

In this study, we revealed the distribution of the AMPA2 glutamate receptor subunit (AMPA2) in the visual cortical areas 17 and 18 of the adult cat by means of different techniques. In situ hybridization, with a cat-specific radioactively labeled oligonucleotide probe, showed that AMPA2 mRNA was expressed mainly in cortical layers II/III and V/VI with a lower expression in layer IV and practically no signal in layer I. Immunocytochemistry, using a polyclonal AMPA2 subunit-specific antibody, showed immunoreactivity almost exclusively in the somata and dendrites of pyramidal neurons in cortical layers II/III and V/VI. Only a very faint signal was detected in layer IV. Neurons with little or no AMPA2 have AMPA receptors that are highly permeable to calcium. By determining the location of AMPA2, this study therefore provides a clear examination of the distribution of Ca²⁺-impermeable AMPA receptors over the supra- and infragranular layers of cat visual cortex. The functional implication of the absence of AMPA2 in cortical layer IV and thus the presence of Ca²⁺-permeable AMPA receptors in this layer, is still speculative and has yet to be elucidated.     

Distribution of vesicular glutamate transporter 2 in auditory and song control brain regions in the adult zebra finch (Taeniopygia guttata)

The songbird brain has a system of interconnected nuclei that are specialized for singing and song learning. Wada et al. (2004; J. Comp. Neurol. 476:44–64) found a unique distribution of the mRNAs for glutamate receptor subunits in the song control brain areas of songbirds. In conjunction with data from electrophysiological studies, these finding indicate a role for the glutamatergic neurons and circuits in the song system. This study examines vesicular glutamate transporter 2 (VGLUT2) mRNA and protein expression in the zebra finch brain, particularly in auditory areas and song nuclei. In situ hybridization assays for VGLUT2 mRNA revealed high levels of expression in the ascending auditory nuclei (magnocellular, angular, and laminar nuclei; dorsal part of the lateral mesencephalic nucleus; ovoidal nucleus), high or moderate levels of expression in the telencephalic auditory areas (cudomedial mesopallium, field L, caudomedial nidopallium), and expression in the song nuclei (HVC, lateral magnocellular nucleus of the anterior nidopallium, robust nucleus of the arcopallium), where levels of expression were greater than in the surrounding brain subdivisions. Area X did not show expression of VGLUT2 mRNA. Nuclei in the descending motor pathway (dorsomedial nucleus of the intercollicular complex, retroambigual nucleus, tracheosyringeal motor nucleus of the hypoglossal nerve) expressed VGLUT2 mRNA. The target nuclei of VGLUT2 mRNA‐expressing nuclei showed immunoreactivity for VGLUT2 as well as hybridization signals for the mRNA of glutamate receptor subunits. The present findings demonstrate the origins and targets of glutamatergic neurons and indicate a central role for glutamatergic circuits in the auditory and song systems in songbirds. J. Comp. Neurol. 522:2129–2151, 2014. © 2013 Wiley Periodicals, Inc.     

Delayed c-fos proto-oncogene expression in the rat hippocampus induced by transient global cerebral ischemia: an in situ hybridization study

The relative levels of c-fos mRNA in individual neurons of the hippocampal formation of rats is dramatically increased following 20 min of cerebral ischemia induced by 4-vessel occlusion. After 24 h of recirculation, a number of scattered neurons in the dentate hilus became hybridization positive. This effect appeared to peak between 24 and 48 h. A few neurons in the pyramidal cell layer of CA1 expressed c-fos as early as 24 h, but the most intense labeling in this region was seen at 72 h of recirculation. These results correlate well with the known distribution of delayed ischemic necrosis in the brain.     

Expression of glutamate receptors in the human and rat basal ganglia: Effect of the dopaminergic denervation on AMPA receptor gene expression in the striatopallidal complex in parkinson's disease and rat with 6-OHDA lesion

The overactivity of subthalamopallidal and corticostriatal glutamatergic neurons observed in Parkinson's disease (PD) suggests that antagonists of glutamate receptor could be used to alleviate the motor symptoms of the disease. In this study, we analysed two features of the striatopallidal complex: (1) the distribution of α-amino-3 hydroxy-5-methyl-4-isoxasol-propionate (AMPA) and kainate receptors and their corresponding mRNA by immunohistochemistry and in situ hybridisation and (2) the effect of dopaminergic denervation on AMPA receptor gene expression in PD patients and rats with 6-hydroxydopamine (6-OHDA)-induced degeneration of the nigrostriatal dopaminergic system. All AMPA receptor mRNAs and proteins (GluR1–4) were detected in the internal segment of the globus pallidus (GPi). Among kainate receptors, only KA1 and KA2 were detectable and only at a low level. Only GluR4 protein was detected in the neuropil of the GPi. In the striatum, GluR1, GluR2, and GluR3 were detected in about 70% of medium-sized and large neurons. By contrast, GluR4 mRNA was detected in only a small number of large and medium-sized neurons. Among kainate receptors, GluR6, GluR7, and KA2 were detected in about 50–60% of medium-sized neurons, whereas GluR5 and KA1 were restricted to 1–2% and 20–30% of these neurons, respectively. These results suggest that antagonists of AMPA and kainate receptors could be effective in alleviating motor symptoms in Parkinson's disease by blocking the overstimulation of pallidal and striatal neurons by glutamate. A significant decrease in GLuR1 gene expression (−33%) was observed in the neurons of the GPi in PD patients and in rat entopeduncular nucleus ipsilateral to the 6-OHDA lesion (−20%). GluR2, GluR3, and GluR4 mRNA levels in the GPi and GluR1–4 mRNA levels in the striatum were unchanged in PD patients and 6-OHDA-lesioned rats compared with their respective controls. These data suggest that dopamine positively regulates only GluR1 gene expression in the GPi. © 1996 Wiley-Liss, Inc.     

Developmental expression of neuronal calmodulin mRNA species in the rat brain analyzed by in situ hybridization.

The temporal and spatial distribution of calmodulin mRNAs which are preferentially expressed in neurons was determined during postnatal development of rat central nervous system. Expression of these mRNAs was strongly detected in the developing neocortex, hippocampus, and cerebellum. Differences in the pattern of expression of a 1.8 and 4.0 kb neuronal calmodulin mRNA species were identified in the developing cerebellum. Expression of the smaller mRNA appeared to correlate with proliferating and developing cerebellar granule neurons while the larger mRNA was present in the mature granule neuron population. A transient elevation in the neuronal calmodulin mRNA species was observed in the superior and inferior colliculus and in the thalamus at postnatal days 5 and 10.