Modulation of the levels of NMDA receptor subunit mRNA and the bindings of [3H]MK-801 in rat brain by chronic infusion of subtoxic dose of MK-801 (original) (raw)
Related papers
Neuroscience Research Communications, 1996
The relationship between the NMDA receptor NR1 subunit mRNA and the binding of the NMDA channel ligand [3H]MK-801 was studied during the late embryonic and early postnatal period in various regions of the rat CNS. NR1 mRNA was detectable at embryonic day 18 in all regions analysed and I specific binding sites for [3H]MK-801 were present in the cerebral cortex at least from the day of birth, with an unaltered affdty up to postnatal day 15. In the cortex, hippocampus and hypothalamus there was a pronounced increase in binding between postnatal day 8 and 15, while the NR1 mRNA levels during this period were unchanged or even decreased. A more parallel developmental profile of mRNA content and binding levels were seen in the medulla and spinal cord. In the cerebellum the profile was different compared to the other regions, with a clear increase in NR1 mRNA between postnatal day 8 and 15 without any change in the [3H]MK-801 binding level. We conclude that even though the NR1 subunit alone possesses all the properties characteristic for the NMDA receptor, we cannot find a clear relationship between the level of its rnRNA and the amount of [3H]MK-801 binding in the developing rat CNS.
Neurodegeneration, 1996
Neuroprotection against excitotoxicity by a combined therapy with the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 and the L-type Ca 2+ channel blocker nimodipine was examined using an in vivo rat model of NMDA-induced neurodegeneration. Attention was focused on the neuroprotective potential of this combined drug treatment before and after NMDA-exposure. NMDA was unilaterally injected in the magnocellular nucleus basalis (MBN). Neuronal damage was assessed 12 days after the NMDA-injection by measuring the reduction of cholinergic cortical fibres that originate from the MBN neurons. In controls that received no drug treatment, NMDA-exposure damaged MBN neurons such that 66% of the cholinergic terminals were lost in the ipsilateral parietal cortex. Pretreatment with a nimodipine diet (860 ppm) combined with application of MK-801 (5 mg/kg i.p.) before NMDA-exposure reduced fibre loss by 89% thereby providing a near complete neuroprotection. Combined therapy of MK-801 (5 mg/kg i.p.) and nimodipine (15 mg/kg i.p.) 8 min after NMDA-infusion reduced neuronal injury by 82%, while the same combination given 2 h after the excitotoxic treatment still yielded a 66% protection against neurotoxic damage invoked by NMDA. In conclusion, the present data show that a dual blockade of NMDA-channels and voltage-dependent calcium channels (VDCC's) up to 2 h after NMDA-exposure is able to provide a significant protection against NMDA-neurotoxicity.
Mechanism Underlying Protective Effect of MK-801 Against NMDA-Induced Neuronal Injury In Vivo
Journal of Cerebral Blood Flow & Metabolism, 1991
The effects of the N-methyl-o-aspartate (NMDA) receptor antagonist MK-801 and the dihydro pyridine calcium antagonist nimodipine on NMDA induced phenomena were investigated using an in vivo fluorometric technique with indo-I. Indo-I, a fluorescent cytosolic free calcium ([Ca2 + l) indicator, was loaded into the cat cortex approximately 500 f.l.m in depth by super fusion with the membrane-permeant indo-I acetoxy methyl ester (indo-I-AM). Changes in [Ca2 + li signals (400 and 506 nm) and reduced nicotinamide adenine di nucleotide (NADH) fluorescence (464 nm) were simulta neously measured directly from the cortex during ultra violet excitation (340 nm). Superfusion of 100 f.l.M NMDA
Neurochemistry International, 2012
Dopamine D1 receptor (D1R) ligands may directly interact with the NMDA receptor (NMDAR), but detailed knowledge about this effect is lacking. Here we identify D1R ligands that directly modulate NMDARs and examine the contributions of NR2A and NR2B subunits to these interactions. Binding of the open channel blocker [ 3 H]MK-801 in membrane preparations from rat-and mouse brain was used as a biochemical measure of the functional state of the NMDAR channel. We show that both D1R agonist A-68930 and dopamine receptor D2 antagonist haloperidol can decrease [ 3 H]MK-801 binding with increased potency in membranes from the NR2A-/mice (i.e. in membranes containing NR2B only), as compared to the inhibition obtained in wild-type membranes. Further, a wide range of D1R agonists such as A-68930, SKF-83959, SKF-83822, SKF-38393 and dihydrexidine were able to decrease [ 3 H]MK-801 binding, all showing half maximal inhibitory concentrations $20 lM, and with significant effects occurring at or above 1 lM. With membranes from D1R-/mice, we demonstrate that these effects occurred through a D1R-independent mechanism. Our results demonstrate that dopamine receptor ligands can selectively influence NR2B containing NMDARs, and we characterize direct inhibitory NMDAR effects by different D1R ligands.
Neuropharmacology, 2001
We have observed that systemic treatment with the uncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist MK-801 increases Src expression and NMDA receptor phosphorylation in rat brain. A partial cDNA encoding rat neuronal Src was isolated and its sequence was used to design specific oligonucleotide probes. Systemically administered MK-801 (5 mg/kg for 4 h) increased by 28±4% mRNA expression of neuronal Src in the superficial layers of the parietal cortex. This effect was observed at doses as low as 0.2 mg/kg. A similar, although more modest, induction was observed 6 h after phencyclidine (15 mg/kg) administration, but not after high doses of memantine and ketamine. The MK-801-induced effect was not blocked by pretreatment with clozapine. Consistent with the increase in mRNA levels, cortical Src protein was increased to 186 ± 24% of control 24 h after MK-801 treatment. Total cellular Src activity was also increased in parietal cortex homogenates 4 h after MK-801 (5 mg/kg). Moreover, MK-801 treatment (0.5 mg/kg and 5 mg/kg for 4 h) increased tyrosine phosphorylation, but not protein levels, of the NMDA receptor subunit NR2A. These results provide evidence for a contribution of Src and tyrosine phosphorylation of NMDA receptors in the pharmacological actions of uncompetitive NMDA receptor antagonists.
Experimental and Toxicologic Pathology, 2003
reviewed the various neurotoxic tests applied in different experimental studies (BELTRAMINO et al. 1993; FIX et al. 1996; O'CALLAHAN and JENSEN 1992). In some cases, the drug used had a highly localized effect on particular CNS structures. Prototypes of such drugs are Phencyclidine (PCP), Ketamine (KTA) and Dizocilpine maleate (MK-801), all of which are non-competitive NMDA receptor antagonists (KEMP et al. 1987). To detect the neurotoxic effect induced by these drugs, numerous staining procedures have been used. Authors using the Hematoxylin-Eosine (H&E) technique have detected cytoplasmic vacuoles in eosinophilic neurons of animals treated with NMDA antagonists (AUER 1996; FIX et al. 1996; OLNEY et al. 1989). The vacuoles have a maximum concentration 4-6 hours after treatment but they are no longer detectable after 24 hs. Immunohistochemical and immunocytochemical techniques have been used to reveal induction of immediate early genes (IEGs) in rats treated with PCP, KTA or MK-801 (FIX et al. 1996; GAO et al. 1998; GASS et al. 1993; NAKKI et al. 1996). Although the IEGs are rapidly induced in the CNS after stress, their detection does not reveal if the changes precede the neuronal degeneration, or whether the damage is transient or irreversible (GON
Neurotoxicology and Teratology, 2010
Non-competitive NMDA-receptor-antagonist drugs such as dizocilpine (MK801) induce behavioral changes and neurotoxicity that have made an impact in different fields of neuroscience. New approaches in research use transgenic mice to elucidate cellular mechanisms and circuits involved in the effects of these drugs. However, the neurodegeneration induced by these drugs has been extensively studied in rats, but the data in mice is limited. Therefore it is important to characterize if the neurotoxic pattern in mice corresponds to that of rats. A comparative analysis of the neurodegeneration induced by MK801 (10 mg/kg) between Wistar rats, and CD-1, CF-1, and C57BL/6-129/Sv mice of both sexes, at different survival times (15, 24, 32, 48, 56 and 72 h) was analysed with the amino-cupric-silver and fluoro-jade B techniques. To compare different administration patterns, groups of mice received subchronic treatments with different doses (final doses of 20 and 40 mg/kg). Results showed that mice treated with MK801 presented different neurotoxic profiles, such as excitotoxiclike cell death in the retrosplenial cortex, terminal degeneration in CA1 and apoptotic-like degeneration in the olfactory bulb. Unlike rats, mice subjected to the same treatment failed to show neurodegeneration in corticolimbic areas such as piriform cortex and dentate gyrus. The amount of degeneration was lower in mice, and the subchronic administration of MK801 did not change the neurotoxic pattern. Additionally, mice lacked the sexually dimorphic response to MK801 toxicity observed in rats. Altogether these results indicate important species dissimilarities. Neurotoxicological studies aimed to explore pathways and mechanisms of MK801 toxicity should consider these differences when using mice as rodent models.
The Cerebellum, 2005
NMDA receptors modulate important cerebral processes such as synaptic plasticity, long-term potentiation, learning and memory, etc. NMDA receptors in cerebellum have specific characteristics that make their function and modulation different from those of NMDA receptors in other brain areas. In this and the accompanying review we summarize the information available on the modulation of NMDA receptors in cerebellum. We review the properties of the NMDA receptor that modulate its function: subunit composition, post-translational modifications and synaptic localization. NMDA receptors are heteromeric ligand-gated ion channels assembled from two families of subunits, NR1 and NR2. There are at least eight splicing variant isoforms of the NR1 subunit and four types of NR2 subunits: NR2A, NR2B, NR2C and NR2D. NMDA receptors with different subunit composition or different splice variants of NR1 subunit have different properties. The expression of the different subunits and splicing variants varies during development. Two special characteristics of NMDA receptors in cerebellum that do not occur in other brain areas are the enrichment in the NR2C subunit and in the splice variant NR1b. As a consequence of these and other factors the pharmacology of NMDA receptors is also different in cerebellum than in other brain areas. The function and localization of NMDA receptors is also modulated by postranslational modifications including phosphorylation, glycosylation and nytrosylation. NMDA receptors are phosphorylated in serines of both NR1 and NR2 subunits and in tyrosines of NR2 subunits.
Down-regulation of NMDA receptor activity by NMDA
Neuroscience Letters, 1993
Rat cerebellar granule cells were cultured in a medium containing 25 mM KC1. The presence of NMDA during culture caused strong downregulation of 45Ca uptake through the NMDA receptor channel. The process affected neither the viability nor the protein content of the cells. The developmental program of NMDA receptor activity was resumed after removal of NMDA from the culture medium, dependent apparently on protein synthesis. The down-regulation also rendered the neurons resistant to NMDA toxicity. It permitted replenishment of the culture with fresh medium, which is extremely toxic for cells cultured in absence of NMDA. Such down-regulation might perhaps play a role in adjusting the activity of post synaptic NMDA receptors, following synaptogenesis.