Hypoxic preconditioning attenuated in kainic acid-induced neurotoxicity in rat hippocampus

The neuroprotective effect of hypoxic preconditioning on kainate (KA)-induced neurotoxicity, including apoptosis and necrosis, was investigated in rat hippocampus. Female Wistar-Kyoto rats were subjected to 380 mm Hg in an altitude chamber for 15 h/day for 28 days. Intrahippocampal infusion of KA was performed in chloral hydrate anesthetized rats, which acutely elevated 2,3-dihydroxybenzoic acid levels in normoxic rats. Seven days after the infusion, KA increased lipid peroxidation in the infused hippocampus and resulted in hippocampal CA3 neuronal loss. A 4-week hypoxic preconditioning attenuated KA-induced elevation in hydroxyl radical formation and lipid peroxidation as well as KA-induced neuronal loss. The effects of hypoxic preconditioning on KA-induced apoptosis and necrosis were investigated further. Two hours after KA infusion, cytosolic cytochrome c content was increased in the infused hippocampus. Twenty-four hours after KA infusion, pyknotic nuclei, cellular shrinkage, and cytoplasmic disintegration, but not TUNEL-positive staining, were observed in the CA3 region of hippocampus. Forty-eight hours after KA infusion, both DNA smear and DNA fragmentation were demonstrated in the infused hippocampus. Furthermore, TUNEL-positive cells, indicative of apoptosis, in the infused hippocampus were detected 72 h after KA infusion. Hypoxic pretreatment significantly reduced necrotic-like events in the KA-infused hippocampus. Moreover, hypoxic preconditioning attenuated apoptosis induced by KA infusion, including elevation in cytosolic cytochrome c content, TUNEL-positive cells, and DNA fragmentation. Our data suggest that hypoxic preconditioning may exert its neuroprotection of KA-induced oxidative injuries via attenuating both apoptosis and necrosis in rat hippocampus.     

Post-ischemic and kainic acid-induced c-fos protein expression in the rat hippocampus

The c-fos protein is a gene regulatory third messenger involved in long-term responses of cells to various stimuli. It can be used as a marker of neuronal activity. In the present immunohistochemical study the presence of c-fos protein (FP) in the rat brain from 1 h to 14 days after 10 min of cerebral ischemia was compared with that 3 h after an intraventricular injection of kainic acid. The kainic acid injection resulted in staining of dentate hilar cells, granule cells and hippocampal interneurones. The postischemic changes at Day 1 were sporadic CA1 pyramidal cells expressing the FP. At Day 2 FP was expressed with variable intensity in many pyramidal cells in the CA1. At Day 3 many necrotic CA1 pyramidal cells were seen. They did not express the FP, and the expression was less intense and found in fewer cells than at Day 2. At Days 3, 7 and 14 there was increasing gliosis without c-fos expression in the CA1. The study demonstrates a delayed postischemic synthesis of the gene regulatory protein c-fos preceding the necrosis in the selectively vulnerable CA1 region.     

Implication of delta opioid receptor subtype 2 but not delta opioid receptor subtype 1 in the development of morphine analgesic tolerance in a rat model of chronic inflammatory pain

Opioids are well known for their robust analgesic effects. Chronic activation of mu opioid receptors (MOPs) is, however, accompanied by various unwanted effects such as analgesic tolerance. Among other mechanisms, interactions between MOPs and delta opioid receptors (DOPs) are thought to play an important role in morphine‐induced behavioral adaptations. Interestingly, certain conditions such as inflammation enhance the function of the DOP through a MOP‐dependent mechanism. Here, we investigated the role of DOPs during the development of morphine tolerance in an animal model of chronic inflammatory pain. Using behavioral approaches, we first established that repeated systemic morphine treatment induced morphine analgesic tolerance in rats coping with chronic inflammatory pain. We then observed that blockade of DOPs with subcutaneous naltrindole (NTI), a selective DOP antagonist, significantly attenuated the development of morphine tolerance in a dose‐dependent manner. We confirmed that this effect was DOP mediated by showing that an acute injection of NTI had no effect on morphine‐induced analgesia in naive animals. Previous pharmacological characterizations revealed the existence of DOP subtype 1 and DOP subtype 2. As opposed to NTI, 7‐benzylidenenaltrexone and naltriben were reported to be selective DOP subtype 1 and DOP subtype 2 antagonists, respectively. Interestingly, naltriben but not 7‐benzylidenenaltrexone was able to attenuate the development of morphine analgesic tolerance in inflamed rats. Altogether, our results suggest that targeting of DOP subtype 2 with antagonists provides a valuable strategy to attenuate the analgesic tolerance that develops after repeated morphine administration in the setting of chronic inflammatory pain.     

红藻氨酸致痫后大鼠海马ERK、P38 MAPK和JNK的活性变化

目的研究红藻氨酸(KA)诱导大鼠癫痫发作后海马组织细胞外调节蛋白激酶(ERK)、p38MAPK和c-jun氨基末端激酶(JNK)的活性(磷酸化状态)的变化情况。方法立体定向大鼠侧脑室内注射KA引起大鼠癫痫发作,采用Western-blot方法观察KA致痫后大鼠海马中活性ERK、p38MAPK和JNK的变化。结果KA诱导大鼠癫痫发作后,海马组织ERK、p38MAPK和JNK的磷酸化水平开始增高,分别于30min、1h和30min后达高峰,呈对照组的4.76倍、2.16倍和3.95倍,两组比较差异具有显著性(P<0.01),之后逐渐下降。结论KA致痫大鼠癫痫发作后,海马组织MAPKs的活性产生变化,其信号通路可能参与癫痫发作后海马组织的病理生理反应过程。     

Opioid peptide release in the rat hippocampus after kainic acid-induced status epilepticus

It has been suggested that kainic acid enhances opioid peptide release. However, no direct evidence exists to support this hypothesis. The main aim of the present study was to determine whether such release occurs in the hippocampus of the rat after status epilepticus induced by kainic acid. Microdialysis experiments revealed significant opioid peptide release in the hippocampus 90-150 min (100%) and 270-300 min (50%) after kainic acid-induced status epilepticus. The peptides released were identified by high-performance liquid chromatography linked to radioimmunoassay as Met-enkephalin, Leu-enkephalin, Dynorphin-A (1-6), and Dynorphin-A (1-8). Reduced extracellular opioid peptide immunoreactivity was detected 28 days after status epilepticus (38% compared with control situation). The present results indicate an important activation of opioid peptide systems by kainic acid-induced status epilepticus. In addition, the reduced hippocampal extracellular opioid peptide levels long-term after kainic acid administration could have important implications for the progressive nature of epileptogenesis.     

Hypoxia modulates cholinergic but not opioid activation of G proteins in rat hippocampus

Intermittent hypoxia, such as that associated with obstructive sleep apnea, can cause neuronal death and neurobehavioral dysfunction. The cellular and molecular mechanisms through which hypoxia alter hippocampal function are incompletely understood. This study used in vitro [(35)S]guanylyl-5'-O-(gamma-thio)-triphosphate ([(35)S]GTP gamma S) autoradiography to test the hypothesis that carbachol and DAMGO activate hippocampal G proteins. In addition, this study tested the hypothesis that in vivo exposure to different oxygen (O(2)) concentrations causes a differential activation of G proteins in the CA1, CA3, and dentate gyrus (DG) regions of the hippocampus. G protein activation was quantified as nCi/g tissue in CA1, CA3, and DG from rats housed for 14 days under one of three different oxygen conditions: normoxic (21% O(2)) room air, or hypoxia (10% O(2)) that was intermittent or sustained. Across all regions of the hippocampus, activation of G proteins by the cholinergic agonist carbachol and the mu opioid agonist [D-Ala(2), N-Met-Phe(4), Gly(5)] enkephalin (DAMGO) was ordered by the degree of hypoxia such that sustained hypoxia > intermittent hypoxia > room air. Carbachol increased G protein activation during sustained hypoxia (38%), intermittent hypoxia (29%), and room air (27%). DAMGO also activated G proteins during sustained hypoxia (52%), intermittent hypoxia (48%), and room air (43%). Region-specific comparisons of G protein activation revealed that the DG showed significantly less activation by carbachol following intermittent hypoxia and sustained hypoxia than the CA1. Considered together, the results suggest the potential for hypoxia to alter hippocampal function by blunting the cholinergic activation of G proteins within the DG.     

Localization of delta opioid receptor immunoreactivity in interneurons and pyramidal cells in the rat hippocampus

To study possible cellular targets and subcellular sites of action of opioid ligands in the rat hippocampus, we examined the distribution of the delta opioid receptor (DOR) by immunocytochemistry. By light microscopy, numerous interneurons, or non-principal cells, were intensely labeled for DOR, whereas the CA1 and CA3 pyramidal cells were lightly labeled. DOR-immunoreactive interneurons were found throughout the hippocampus but were particularly concentrated in stratum oriens of the CA1 region. Double labeling immunofluorescence revealed that DOR-immunoreactivity was found in a subpopulation of γ-aminobutyric acid (GABA)-containing interneurons, which included most somatostatin-immunoreactive cells. Electron microscopic analysis of sections singly labeled for DOR revealed that DOR-immunoreactive profiles were abundant and widespread throughout all hippocampal lamina and had a similar distribution in CA1 and CA3. DOR-immunoreactivity was sometimes found in dendrites, which corresponded in morphology to those of interneurons. In addition, DOR-labeling was found in the shafts and spines of many dendrites, which exhibited the morphology of pyramidal cell dendrites. Within dendrites, dense DOR-immunoreactivity was associated with the plasmalemmal surface at or near the postsynaptic density, usually of asymmetric synapses. In addition, DOR labeling was present in a heterogeneous population of axon terminals, as well as in astrocytic profiles. At mossy fiber synapses, DOR labeling was occasionally found at both pre-and post-synaptic sites. These studies demonstrate that DOR is present at multiple sites on diverse cell types where it may function to regulate neuronal activity in the hippocampus. J. Comp. Neurol. 373-387, 1997. © 1997 Wiley-Liss, Inc.     

Mu and delta opioid receptor regulation of pro-opiomelanocortin peptide secretion from the rat neurointermediate pituitary in vitro

We investigated the ability of selective opioid agonists and antagonists to influence pro-opiomelanocortin peptide secretion from the rat neurointermediate lobe in vitro. The mu-opioid agonist DAMGO ([D-Ala(2), N-Me-Phe(4), Gly(5)-ol]enkephalin) significantly stimulated beta-endorphin and alpha-melanocyte-stimulating hormone release relative to controls early (30 min) in the incubation period. Similar effects on beta-endorphin secretion were observed with the selective mu-opioid agonist dermorphin. The delta-opioid receptor agonist DPDPE ([D-Pen(2,5)]enkephalin) weakly inhibited beta-endorphin secretion relative to controls while the kappa-opioid receptor agonist U50488 had no effect. The mu-opioid selective antagonist CTOP (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2)) inhibited basal beta-endorphin secretion while kappa- and delta-opioid receptor antagonists had no effect. Our data support a role for local mu-opioid receptor control of intermediate lobe pro-opiomelanocortin peptide secretion. Peptide secretion from melanotropes appears to be tonically stimulated by activation of mu-opioid receptors in the absence of intact neuronal innervation to the intermediate lobe.     

Enhanced cell-to-cell contacts between activated microglia and pyramidal cell dendrites following kainic acid-induced neurotoxicity in the hippocampus

Microglia participate in immune responses in the brain. However, little is known about the contact-mediated interaction between microglia and neurons. We report here that the cell-to-cell contacts between microglial processes and dendrites of hippocampal CA1 neurons were dramatically increased in density and area following local injection of kainic acid (KA). A similar KA-induced increase in the degree of intercellular contacts was observed in mice lacking telencephalin (TLCN), a neuronal dendritic adhesion molecule of ICAM family. The results suggest that adhesive contacts independent of TLCN and contact-mediated interactions between microglia and dendrites were promoted by excitotoxic brain injury.     

Soman- or kainic acid-induced convulsions decrease muscarinic receptors but not benzodiazepine receptors

[3H]Quinuclidinyl benzilate (QNB) binding to muscarinic receptors decreased in the rat forebrain after convulsions induced by a single dose of either soman, a potent inhibitor of acetylcholinesterase, or kainic acid, an excitotoxin. A Rosenthal plot revealed that the receptors decreased in number rather than affinity. When the soman-induced convulsions were blocked, the decrease in muscarinic receptors at 3 days was less extensive than when convulsions occurred and at 10 days they approached control levels in most of the brain areas. The most prominent decrements in QNB binding were in the piriform cortex where the decline in QNB binding is probably related to the extensive convulsion-associated neuropathology. The decrements in QNB binding after convulsions suggest that the convulsive state leads to a down-regulation of muscarinic receptors in some brain areas. In contrast to the decrease in QNB binding after convulsions, [3H]flunitrazepam binding to benzodiazepine receptors did not change even in the piriform cortex where the loss in muscarinic receptors was most prominent. Thus, it appears that those neuronal processes that bear muscarinic receptors are more vulnerable to convulsion-induced change than those with benzodiazepine receptors.     

Ginsenosides attenuate kainic acid-induced synaptosomal oxidative stress via stimulation of adenosine A(2A) receptors in rat hippocampus

Treatment with ginsenosides attenuated KA-induced seizures and oxidative stress in the synaptosome, and reduced synaptic vesicles at the presynaptic terminals dose-dependently. The adenosine A(2A) receptor antagonist 1,3,7-trimethyl-8-(3-chlorostyryl) xanthine reversed the ginsenoside-mediated pharmacological actions. Neither the adenosine A(1) receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine nor the adenosine A(2B) receptor antagonist alloxazine affected the ginsenoside-mediated pharmacological actions. Our results suggest that ginsenosides block KA-induced synaptosomal oxidative stress, associated with hippocampal degeneration, through activation of adenosine A(2A) receptors.     

Mu and delta opiate receptors in rat brain are affected by GTP but not by MIF-1

The possible competition of MIF-1 (Pro-Leu-Gly-NH2) with 3H-naloxone or 3H-D-Ala-D-Leu-enkephalin (DADLE) for mu and delta opiate receptors in the rat striatum was examined under conditions of varying temperatures and concentrations of sodium and GTP. MIF-1, in concentrations ranging from 10(-14) to 10(-3) M, failed to compete with either 3H-DADLE or 3H-naloxone for delta or mu receptors, GTP (2 microM) facilitated binding (17.7 +/- 1.9%) at all concentrations of MIF-1 in the 1H-DADLE assay; unexpectedly, GTP facilitated binding in the 3H-naloxone assay (11.5 +/- 1.3%) under conditions used to potentiate antagonist binding (addition of NaCl and incubation at 4 degrees C). GTP showed optimal facilitation at a concentration of about 2 microM in both the 3H-DADLE and 3H-naloxone "antagonist" conditions. At higher doses of GTP, 3H-naloxone binding remained high, but 3H-DADLE binding decreased to near or below control values. MIF-1 did not affect these GTP responses, indicating further the lack of effect of this peptide on opiate binding.     

Inhibitors of NO-synthase and donors of NO modulate kainic acid-induced damage in the rat hippocampus

The effects of nitric oxide synthase (NOS) inhibitors, N(omega)-nitro-L-arginine and 7-nitroindazole, and the NOS substrate L-arginine on kainic acid (KA)-induced microglial reactivity and stress response were studied in the hippocampus 7 and 1 days after KA, respectively. Density of peripheral-type benzodiazepine receptors was measured as an index of microglial reactivity. Histological damage in hippocampus was evaluated at 7 days by neuronal counting. KA increased the maximal number of binding sites (B(max)) versus controls. Administration of either 7-nitroindazole (25 mg/kg) or N(omega)-nitro-L-arginine (20 and 50 mg/kg) 24 hr before KA, further increased B(max). This later effect was abolished by L-arginine (1 g/kg), which given 24 hr before KA decreased B(max) to control values. Also, KA-induced HSP72 stress response was attenuated by pre-treatment with L-arginine. Histological evaluation showed reduced cell numbers in the pyramidal cell layer of the hippocampus in groups receiving KA, either alone or in combination with 7-nitroindazole. Administration of L-arginine before KA attenuated neuronal loss in CA3 but not CA1. A clear protective effect was observed, however, in CA1 and CA3, in rats receiving both L-arginine plus 7-nitroindazole before KA. The results show that the combination of a NO substrate with a NOS inhibitor reduces the neurotoxic effects of KA in the rat hippocampus. This study suggests that extremely fine regulation of NO levels in the different neural cell types can modulate excitotoxicity.     

Domoic acid-induced neurotoxicity in the hippocampus of adult rats

Domoic acid (DA), an agonist of non-N-methyl-D-aspartate (non-NMDA) receptor subtype including kainate receptor, was identified as a potent neurotoxin showing involvement in neuropathological processes like neuronal degeneration and atrophy. In the past decade evidence indicating a role for excitatory amino acids in association with neurological disorders has been accumulating. Although the mechanisms underlying the neuronal damage induced by DA are not yet fully understood, many intracellular processes are thought to contribute towards DA-induced excitotoxic injury, acting in combination leading to cell death. In this review article, we report the leading hypotheses in the understanding of DA-induced neurotoxicity, which focus on the role of DA in neuropathological manifestations, the formation of the retrograde messenger molecule nitric oxide (NO) for the production of free radicals in the development of neuronal damage, the activation of glial cells (microglia and astrocytes) in response to DA-induced neuronal damage and the neuroprotective role of melatonin as a free radical scavenger or antioxidant in DA-induced neurotoxicity. The possible implications of molecular mechanism underlying the neurotoxicity in association with necrosis, apoptosis, nitric oxide synthases (nNOS and iNOS) and glutamate receptors (NMDAR1 and GluR2) related genes and their expression in DA-induced neuronal damage in the hippocampus have been discussed.     

Regulation of X-chromosome-linked inhibitor of apoptosis protein in kainic acid-induced neuronal death in the rat hippocampus

XIAP (X-chromosome-linked inhibitor of apoptosis protein) is an antiapoptotic protein which inhibits the activity of caspases and suppresses cell death. However, little is known about the presence and function of XIAP in the nervous system. Here we report that XIAP mRNA is expressed in developing and adult rat brain. Using a specific antibody, we observed XIAP-immunoreactive cells in different brain regions, among others, in the hippocampus and cerebral cortex. Kainic acid, which induces delayed cell death of specific neurons, increased the levels of XIAP in the CA3 region of hippocampus. XIAP was, however, largely absent in cells undergoing cell death, as shown by TUNEL labeling and staining for active caspase-3. In cultured hippocampal neurons, XIAP was initially upregulated by kainic acid and then degraded in a process blocked by the caspase-3 inhibitor DEVD. Similarly, recombinant XIAP is cleaved by active caspase-3 in vitro. The results show that there is biphasic regulation of XIAP in the hippocampus following kainic acid and that XIAP becomes a target for caspase-3 activated during cell death in the hippocampus. The degradation of XIAP by kainic acid contributes to neuronal cell death observed in vulnerable neurons of the hippocampus after caspase activation.     

Mu,delta, and kappa opioid receptor mRNA expression in the rat CNS: An in situ hybridization study

The μ, δ, and κ opioid receptors are the three main types of opioid receptors round in the central nervous system (CNS) and periphery. These receptors and the peptides with which they interact are important in a number of physiological functions, including analgesia, respiration, and hormonal regulation. This study examines the expression of μ, δ, and κ receptor mRNAs in the rat brain and spinal cord using in situ hybridization techniques. Tissue sections were hybridized with ³⁵S-labeled cRNA probes to the rat μ (744–1, 064 b), δ (304–1,287 b), and κ (1,351–2,124 b) receptors. Each mRNA demonstrates a distinct anatomical distribution that corresponds well to known receptor binding distributions. Cells expressing μ receptor mRNA are localized in such regions as the olfactory bulb, caudate-putamen, nucleus accumbens, lateral and medial septum, diagonal band of Broca, bed nucleus of the stria terminalis, most thalamic nuclei, hippocampus, amygdala, medial preoptic area, superior and inferior colliculi, central gray, dorsal and median raphe, raphe magnus, locus coeruleus, parabrachial nucleus, pontine and medullary reticular nuclei, nucleus ambiguus, nucleus of the solitary tract, nucleus gracilis and cuneatus, dorsal motor nucleus of vagus, spinal cord, and dorsal root ganglia. Cellular localization of δ receptor mRNA varied from μ or κ, with expression in such regions as the olfactory bulb, allo- and neocortex, caudate-putamen, nucleus accumbens, olfactory tubercle, ventromedial hypothalamus, hippocampus, amygdala, red nucleus, pontine nuclei, reticulotegmental nucleus, motor and spinal trigeminal, linear nucleus of the medulla, lateral reticular nucleus, spinal cord, and dorsal root ganglia. Cells expressing, κ receptor mRNA demonstrate a third pattern of expression, with cells localized in regions such as the claustrum, endopiriform nucleus, nucleus accumbens, olfactory tubercle, medial preoptic area, bed nucleus of the stria terminalis, amygdala, most hypothalamic nuclei, median eminence, infundibulum, substantia nigra, ventral tegmental area, raphe nuclei, paratrigeminal and spinal trigeminal, nucleus of the solitary tract, spinal cord, and dorsal root ganglia. These findings are discussed in relation to the physiologica functions associated with the opioid receptors.     

Mitochondrial dysfunction and ultrastructural damage in the hippocampus during kainic acid-induced status epilepticus in the rat

PURPOSE: Prolonged and continuous epileptic seizure (status epilepticus) results in cellular changes that lead to neuronal damage. We investigated whether these cellular changes entail mitochondrial dysfunction and ultrastructural damage in the hippocampus, by using a kainic acid (KA)-induced experimental status epilepticus model. METHODS: In Sprague-Dawley rats maintained under chloral hydrate anesthesia, KA (0.5 nmol) was microinjected unilaterally into the CA3 subfield of the hippocampus to induce seizure-like hippocampal EEG activity. The activity of key mitochondrial respiratory chain enzymes in the dentate gyrus (DG), or CA1 or CA3 subfield of the hippocampus was measured 30 or 180 min after application of KA. Ultrastructure of mitochondria in those three hippocampal subfields during KA-induced status epilepticus also was examined with electron microscopy. RESULTS: Microinjection of KA into the CA3 subfield of the hippocampus elicited progressive build-up of seizure-like hippocampal EEG activity. Enzyme assay revealed significant depression of the activity of nicotinamide adenine dinucleotide cytochrome c reductase (marker for Complexes I+III) in the DG, or CA1 or CA3 subfields 180 min after KA-elicited temporal lobe status epilepticus. Conversely, the activities of succinate cytochrome c reductase (marker for Complexes II+III) and cytochrome c oxidase (marker for Complex IV) remained unaltered. Discernible mitochondrial ultrastructural damage, varying from swelling to disruption of membrane integrity, also was observed in the hippocampus 180 min after hippocampal application of KA. CONCLUSIONS: Our results demonstrated that dysfunction of Complex I respiratory chain enzyme and mitochondrial ultrastructural damage in the hippocampus are associated with prolonged seizure during experimental temporal lobe status epilepticus.     

Endogenous adenosine protects CA1 neurons from kainic acid-induced neuronal cell loss in the rat hippocampus

CA3 pyramidal neurons in the rat hippocampus show selective vulnerability to the intracerebroventricular injection of kainic acid (KA). However, the mechanism of this selective neuronal vulnerability remains unclear. In this study, we examined the contribution of endogenous adenosine, a potent inhibitory neuromodulator, to the differences in the neuronal vulnerability of the hippocampus, using microtubule-associated protein (MAP)-2, phosphorylated c-Jun, and major histocompatibility complex (MHC) class II immunoreactivities as markers for neuronal cell loss, neuronal apoptosis and glial activation, respectively. Pretreatment with 8-cyclopenthyltheophylline (CPT), an A1 adenosine receptor antagonist, significantly exacerbated KA-induced neuronal cell loss in both the CA1 and CA3. Although c-Jun phosphorylation, a critical step in neuronal apoptosis, was not detected in the vehicle-injected rat hippocampus, c-Jun phosphorylation was induced in the CA3 by the injection of KA alone. Pretreatment with CPT induced c-Jun phosphorylation in both the CA1 and CA3. MHC class II antigen was also detected in the regions of c-Jun phosphorylation. Coadministration of N6-cyclopenthyladenosine (CHA), an A1 adenosine receptor agonist, attenuated the neuronal cell loss in the CA1 and CA3 with or without pretreatment with CPT. These results strongly suggest that endogenous adenosine has neuroprotective effects against excitotoxin-induced neurodegeneration in the CA1 through its A1 receptors.     

N-methyl-D-aspartate receptor subunit 1 protein expression in the hippocampus and temporal cortex of kainic acid-induced epilepsy rats

BACKGROUND: The N-methyl-D-aspartate receptor subunit 1 (NMDAR1) contributes to the incidence of epilepsy. However, the relationship between epilepsy-induced brain injury and NMDAR1 remains poorly understood.OBJECTIVE: To investigate changes in NMDAR1 protein expression in the hippocampus and temporal cortex of kainic acid-induced epilepsy rats.DESIGN, TIME AND SETrlNG: A randomized, controlled, animal experiment was performed at the Department of Physiology and Department of Pathology, Basic Medical College of Jilin University from March 2002 to March 2003.MATERIALS: Rabbit anti-NMDAR1 antibody was purchased from Wuhan Boster Biological Technology, China.METHODS: A total of 80 healthy, male, Wistar rats, aged 22 weeks, were randomly assigned to sham-surgery (n = 10) and model (n = 70) groups. Epilepsy models were established by injecting kainic acid (1 μL) into the right amygdala, and rats were sacrificed at 2, 6, 24, 72 hours, and 7, 15, 30 days after surgery, with 10 animals at each time point. The rats in the sham-surgery group were injected with 1 μL phosphate buffered saline into the right amygdala.MAIN OUTCOME MEASURES: NMDAR1 protein expression in the hippocampus and temporal cortex at 2, 6, 24, 72 hours and 7, 15, 30 days after epilepsy was detected using immunohistochemistry and flow cytometry analysis.RESULTS: In the sham-surgery group, a few NMDARl-positive cells were distributed in the hippocampus and temporal cortex. In the model group, NMDARl-positive cells were increased in the hippocampus and temporal cortex at 2 hours following kainic acid-induced epilepsy. They were significantly increased at 6 hours, and slightly decreased at 7 days (CA3 region and temporal cortex), but remained greater than the sham-surgery group. This continued until day 30 (P < 0.01). In addition, there were more NMDAR1 positive cells in the hippocampal CA3 and dentate gyrus than the temporal cortex (P < 0.01).CONCLUSION: In epilepsy model rats, NMDAR1 protein expression was upregulated in the hippocampus and temporal cortex, and in particular in the hippocampal CA3 and dentate gyrus. NMDAR1 may participate in epilepsy and the excitation process of the epileptic brain.