奥氮平对谷氨酸功能低下的精神分裂症小鼠模型的作用

目的 观察奥氮平对谷氨酸功能低下小鼠模型表现出的高活动性及前脉冲抑制(PPI)缺失的作用.方法 昆明种小鼠165只.(1)取36只小鼠分为4组:溶媒空白对照组(腹腔注射溶媒,以下简称对照组),3种奥氮平剂量(0.1 mg/kg体质量,0.2 mg/kg体质量,0.3 mg/kg体质量,腹腔注射)组,每组8～10只;观察奥氮平对小鼠探究行为和自主活动的影响.(2)取49只小鼠分为5组:对照组,地卓西平马来酸盐(MK-801)模型组(溶媒+MK-801,0.25 mg/kg体质量,腹腔注射),3种剂量(同上)奥氮平干预组(奥氮平+MK-801 0.25 mg/kg体质量,腹腔注射),每组9～10只;观察奥氮平对MK-801致小鼠自主活动增加的影响.(3)取80只小鼠分为8组:对照组,MK-801模型组(溶媒+MK-801,0.5 mg/kg体质量,腹腔注射),3种奥氮平剂量给药组(奥氮平+生理盐水,奥氮平剂量分别为0.3 mg/kg体质量,1 mg/kg体质量,3 mg/kg体质量),3种奥氮平剂量(同上)干预组(奥氮平+MK-801 0.5 mg/kg体质量,腹腔注射),每组10只;观察奥氮平对基线前脉冲抑制(PPI)及MK-801引起的PPI缺失的影响.结果 (1)与对照组比较,奥氮平剂量为0.2 mg/kg体质量和0.3mg/kg体质量时,小鼠的探究行为及自主活动总路程减少(P均＜0.05);但剂量为0.1 mg/kg时,对小鼠的探究行为(P=0.363)及自主活动(P=0.196)无影响.(2)奥氮平剂量为0.1～0.3 mg/kg体质量时,呈剂量依赖性抑制MK-801引起的自主活动增加(P均＜0.05).(3)奥氮平剂量为0.3～3mg/kg体质量时,对基线的PPI无影响(P均＞0.05),剂量为1～3 mg/kg时呈剂量依赖性修复了MK-801引起的PPI缺失(P均＜0.05).结论 奥氮平能够特异性地抑制谷氨酸功能低下小鼠模型表现出的高活动性和PPI缺失,与奥氮平的临床药理作用一致.     

氯氮平对谷氨酸功能低下精神分裂症小鼠模型的作用

目的 观察氯氮平对地卓西平马来酸盐（MK-801）所致谷氨酸功能低下精神分裂症小鼠模型的高活动性及刻板行为的作用。方法 昆明种小鼠130只。（1）取34只小鼠分为4组：溶媒空白对照组（腹腔注射溶媒，以下简称对照组）；3种氯氮平剂量（1．0，1．5，2．0mg／kg体质量，腹腔注射）组；每组8～10只，观察氯氮平对小鼠探究行为和自主活动的影响。（2）取46只小鼠分为5组，分别为对照组、MK-801模型组（溶媒＋MK-801，0．25mg／kg体质量，腹腔注射）及3种剂量（同上）氯氮平组分别加MK-801（0．25mg／kg体质量，腹腔注射），每组8～10只，观察氯氮平对MK-致801小鼠自主活动增加的影响。（3）取50只小鼠，每组10只，给药方案同“（2）”，观察氯氮平对MK-801引起的刻板行为的影响。结果 （1）与对照组比较，氯氮平剂量为1．5mg／kg体质量和2．0mg／kg体质量时，小鼠的探究行为及自主活动总路程减少（P均〈0．001）；但剂量为1．0mg／kg时，对小鼠的探究行为及自主活动均无影响（P均〉0．05）。（2）氯氮平剂量为1．0～2．0mg／kg体质量时，呈剂量依赖性抑制由MK-801引起的自主活动增加（均P〈0．05）。（3）氯氮平剂量为1．5～2．0mg／kg体质量时，呈剂量依赖性抑制MK-801引起的刻板行为（均P〈0．05）。但低剂量（1．0mg／kg体质量）氯氮平对MK-801引起的刻板行为无明显影响（P〉0．05）。结论 氯氮平对MK-801所致谷氨酸功能低下精神分裂症小鼠模型不同脑区的作用有选择性，低剂量时抑制由中脑边缘、中脑皮质系统介导的高活动性，较高剂量时抑制由中脑边缘、中脑皮质系统及黑质纹状体系统控制的高活动性及刻板行为。     

1-Methyl-1,2,3,4-tetrahydroisoquinoline Antagonizes a Rise in Brain Dopamine Metabolism, Glutamate Release in Frontal Cortex and Locomotor Hyperactivity Produced by MK-801 but not the Disruptions of Prepulse Inhibition, and Impairment of Working Memory in Rat

1-Methyl-1,2,3,4-tetrahydroisoquinoline (1MeTIQ) is an endogenous compound that is constantly present in the brain, and that exhibits neuroprotective activity. Our earlier study has suggested that 1MeTIQ may play a crucial physiological role in the mammalian brain as an endogenous regulator of dopaminergic activity. It is well known that central nervous system stimulants such as: amphetamine, cocaine, phencyclidine, and selective NMDA receptor antagonists, e.g., MK-801 produce neuropsychotoxicity (psychosis, addiction) that is indistinguishable from paranoid type schizophrenia. In rodents, phencyclidine and MK-801 are often used to evoke schizophrenia-like behavioral abnormalities which are inhibited by neuroleptics. The present study was designed to further investigate potential antipsychotic properties of 1MeTIQ by using both behavioral and neurochemical studies in the rat. We investigated the influence of 1MeTIQ (25 and 50 mg/kg ip) on locomotor hyperactivity, disruptions of prepulse inhibition (PPI), and working memory impairment induced by the NMDA receptor antagonist, MK-801 (0.2–0.3 mg/kg ip). In addition in the biochemical study, we analyzed the effect of 1MeTIQ on the changes in dopamine metabolism in different brain structures and in extraneuronal release of dopamine and glutamate in the rat frontal cortex, produced by MK-801. The concentration of dopamine (DA) and its metabolites: 3,4-dihydroxyphenylacetic acid (DOPAC), 3-methoxytyramine (3-MT), and homovanillic acid (HVA), as well as the extraneuronal concentration of dopamine and glutamate were established by HPLC. MK-801 (0.25 mg/kg ip) evoked significant disruptions of PPI and working memory impairment, and co-administration of 1MeTIQ at two investigated doses of 25 and 50 mg/kg ip did not antagonize these effects. On the other hand hyperactivity evoked by MK-801 as well as a rise in dopamine metabolism in specific brain structures and glutamate release in the frontal cortex was completely antagonized by pretreatment with 1MeTIQ. If the hyperlocomotion elicited by acutely administered MK-801 is a valid model of at least some aspects of schizophrenia, these results indicate that 1MeTIQ will show efficacy in treating this condition. In conclusions, the present study suggests that 1MeTIQ, an endogenous neuroprotective compound, exhibits also antipsychotic-like efficacy in some animal tests, and may be useful in clinical practice as a psychosis-attenuating drug in schizophrenic patients. However, 1MeTIQ did not attenuate sensorimotor gating deficit or working memory impairment evoked by MK-801 which may be served as a model of negative symptoms of schizophrenia.     

Effect of orally administered guanosine on seizures and death induced by glutamatergic agents

Intraperitoneal guanosine has been shown to prevent quinolinic acid-induced seizures in mice. In this study, we investigated the effect of orally administered guanosine on seizures induced by the glutamate agonists quinolinic acid and kainate, and the endogenous glutamate releaser α-dendrotoxin. Guanosine (7.5 mg/kg, per os), administered 75 min in advance, prevented 70% of seizures induced by i.c.v. quinolinic acid, being as efficient as the NMDA channel blocker MK-801 administered intraperitoneally. Guanosine was ineffective against kainate-induced seizures, but significantly reversed the potentiation of seizures and death caused by the concomitant injection of MK-801. Guanosine also significantly prevented seizures and death induced by i.c.v. α-dendrotoxin, whereas MK-801 and phenobarbital only prevented death. Altogether, our findings underscore the therapeutic potential of oral administration of guanosine for treating diseases involving glutamatergic excitotoxicity, including epilepsy.     

Rodent data and general hypothesis: antipsychotic action exerted through 5-HT2A receptor antagonism is dependent on increased serotonergic tone

Summary. The locomotor stimulation induced by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (dizocilpine) in mice was regarded as a model of at least some aspects of schizophrenia. The serotonin synthesis inhibitor dl-p-chlorophenylalanine (PCPA) was used to evaluate the involvement of endogenous serotonin in (a) the induction of MK-801-induced hyperlocomotion in NMRI mice, and (b) the inhibition of MK-801-induced hyperlocomotion by each of five monoaminergic antagonists (M100907, clozapine, olanzapine, raclopride, SCH23390). Further, brain monoaminergic biochemistry was characterised in rats and mice after various drug treatments. PCPA pretreatment did not significantly reduce MK-801-induced hyperlocomotion in any of the experiments performed; however in a meta-analysis of six experiments, the locomotion displayed by MK-801-treated animals was diminished 17% by PCPA pretreatment. The selective 5-HT2A receptor antagonist M100907 exerted a dose-dependent inhibition of MK-801-induced hyperlocomotion. This effect was abolished in mice pretreated with PCPA, but could be restored in a dose-dependent manner by restitution of endogenous 5-HT by means of 5-hydroxytryptophan (5-HTP). On the other hand, the inhibition of MK-801-induced hyperlocomotion exerted by the selective dopamine D-2 receptor antagonist raclopride or the dopamine D-1 receptor antagonist SCH23390 was unaffected by PCPA pretreatment. The antipsychotics clozapine and olanzapine displayed a split profile. Hence, the inhibitory effect on MK-801-induced hyperlocomotion exerted by low doses of these compounds was diminished after PCPA pretreatment, while inhibition exerted by higher doses was unaffected by PCPA. These results suggest that (1) MK-801-induced hyperlocomotion is accompanied by an activation of, but is not fully dependent upon, brain serotonergic systems. (2) In the hypoglutamatergic state induced by MK-801, endogenous serotonin exerts a stimulatory effect on locomotion through an action at 5-HT2A receptors, an effect that is almost completely counterbalanced by a concomitant inhibitory impact on locomotion, mediated through stimulation of serotonin receptors other than 5-HT2A receptors. M100907, by blocking 5-HT2A receptors, unveils the inhibitory effect exerted on locomotion by these other serotonin receptors. (3) Dopamine D-2 receptor antagonistic properties of antipsychotic compounds, when they come into play, override 5-HT2A receptor antagonism. Possible implications for the treatment of schizophrenia with 5-HT2A receptor antagonists are discussed. It is hypothesized that treatment response to such agents is dependent on increased serotonergic tone. Accepted February 9, 1998; received December 16, 1997     

Decreased hyperlocomotion induced by MK-801, but not amphetamine and caffeine in mice lacking cellular prion protein (PrP(C))

The cellular prion protein (PrP(C)) has been involved in several neurodegenerative disorders however it has been proposed that it is also be implicated in psychotic disorders. We investigated the effect of three psychotropic drugs in locomotor activity of PrP(C) knockout (Prnp(O/O)) and wild-type mice. The NMDA receptor channel blocker MK-801 (0.25 mg/kg), the indirect dopamine agonist amphetamine (1 mg/kg) and the adenosine receptor antagonist caffeine (10 mg/kg) were administered i.p. after 60 min of habituation and locomotion was monitored for 3 h. Prnp(O/O) mice presented a diminished hyperlocomotor response to MK-801 treatment but normal response to amphetamine and caffeine compared to wild type mice. These results suggest that lack of PrP(C) leads to a functional alteration in the glutamatergic system, whereas the regulation of both dopaminergic and adenosinergic systems are preserved. Finally, lack of PrP(C) seems not to exacerbate the response to these psychotropic drugs, which modulate neurotransmitter systems possibly involved in schizophrenia and psychotic disorders.     

NC-1900, an arginine-vasopressin analogue, ameliorates social behavior deficits and hyperlocomotion in MK-801-treated rats: therapeutic implications for schizophrenia

We previously reported that chronic administration of N-methyl-D-aspartate (NMDA) antagonists reduced the density of vasopressin V1a receptors in several brain regions in rats that demonstrated social interaction deficits and increased locomotor activity. These observations indicate the ability of arginine-vasopressin (AVP), or its analogues, to modulate behavioral abnormalities associated with blockade of NMDA receptors. The present study was performed to investigate the effect of NC-1900, an AVP analogue, on social behavior and locomotor activity in rats treated with MK-801, a non-competitive NMDA receptor antagonist. Male Wistar rats were administered MK-801 (0.13 mg/kg/day ip) or saline for 14 days. Social behavior and locomotor activity were measured 45 min after the injection of NC-1900 (10 ng/kg sc) or saline together with the last MK-801 or vehicle administration. Social interaction was quantified by an automated video-tracking system, and stereotyped behavior and ataxia were manually measured. Acute administration of NC-1900 partially reversed MK-801-induced hyperlocomotion and deficits in social interaction, while NC-1900 itself did not affect these behavioral measures in animals chronically treated with vehicle saline. These results suggest that the central AVP system may interact with glutamatergic and dopaminergic transmissions, and indicate potential therapeutic effects of AVP analogues on positive and negative symptoms of schizophrenia.     

Non-NMDA excitatory amino acid receptors in the ventral tegmental area mediate systemic dizocilpine (MK-801) induced hyperlocomotion and dopamine release in the nucleus accumbens

This study investigated the putative role of non-NMDA excitatory amino acid (EAA) receptors in the ventral tegmental area (VTA) for the increase in dopamine (DA) release in the nucleus accumbens (NAC) and behavioral stimulation induced by systemically administered dizocilpine (MK-801). Microdialysis was utilized in freely moving rats implanted with probes in the VTA and NAC. Dialysates from the NAC were analyzed with high-performance liquid chromatography for DA and its metabolites. The VTA was perfused with the AMPA and kainate receptor antagonist CNQX (0.3 or 1 mM) or vehicle. Forty min after onset of CNQX or vehicle perfusion of the VTA, MK-801 (0.1 mg/kg) was injected subcutaneously. Subsequently, typical MK-801 induced behaviors were also assessed in the same animals by direct observation. MK-801 induced hyperlocomotion was associated with a 50% increase of DA levels in NAC dialysates. Both the MK-801 evoked hyperlocomotion and DA release in the NAC was antagonized by CNQX perfusion of the VTA in a concentration-dependent manner. None of the other rated MK-801 evoked behaviors, e.g. head weaving or sniffing, were affected by CNQX perfusion of the VTA. By itself the CNQX or vehicle perfusion of the VTA alone did not affect DA levels in NAC or any of the rated behaviors. These results indicate that MK-801 induced hyperlocomotion and DA release in the NAC are largely elicited within the VTA via activation of non-NMDA EAA receptors, tentatively caused by increased EAA release. Thus, the locomotor stimulation induced by psychotomimetic NMDA receptor antagonists may not only reflect impaired NMDA receptor function, but also enhanced AMPA and/or kainate receptor activation in brain, e.g., in the VTA. In view of their capacity to largely antagonize the behavioral stimulation induced by psychotomimetic drugs, such as MK-801, AMPA, and/or kainate receptor antagonists may possess antipsychotic efficacy. J. Neurosci. Res. 51:583–592, 1998. © 1998 Wiley-Liss, Inc.     

Spontaneous alternation behaviour in rats: kynurenic acid attenuated deficits induced by MK-801

The present study was undertaken to investigate the effects of pharmacological modulation of the NMDA receptors on spontaneous alternation behaviour. The performance of rats treated with MK-801 and kynurenic acid (KYNA) was assessed in the cross-arm-maze. We evaluated: (a) the total number of arm entries representing locomotor activity, (b) spontaneous variation of different arms thought to reflect alternation performance. In the first experiment, MK-801 (0.01, 0.025, 0.05, 0.1 and 0.2 mg/kg, i.p.) was given 30 min prior to the testing. Beginning the dose of 0.05 mg/kg the drug increased locomotion and impaired alternation performance. An ability of animals to enter subsequently three or four different arms was reduced significantly. In the second experiment, the dose of 0.05 mg/kg was chosen as the lowest possible dose of MK-801 producing marked behavioural impairment. KYNA (0.3, 3 and 30 mg/kg, s.c.) was administered 60 min prior to the MK-801. While all KYNA doses prevented hyperlocomotion, only the highest dose (30 mg/kg) maintained alternation score at the control levels, i.e. the KYNA plus MK-801 treated animals alternated regularly three or four different arms. The results suggest different sensitivity of the two behavioural systems, i.e. locomotion and space orientation, towards pharmacological insult. In conclusion, the study confirmed protective behavioural effects of KYNA given in sufficient amounts and sufficiently long prior MK-801.     

The Influence of the CB1 Receptor Ligands on the Schizophrenia-Like Effects in Mice Induced by MK-801

A growing body of psychiatric research has emerged, focusing on the role of endocannabinoid system in psychiatric disorders. For example, the endocannabinoid system, via cannabinoid CB (CB1 and CB2) receptors, is able to control the function of many receptors, such as N-methyl-d-aspartate (NMDA) receptors connected strictly with psychosis or other schizophrenia-associated symptoms. The aim of the present research was to investigate the impact of the CB1 receptor ligands on the symptoms typical for schizophrenia. We provoked psychosis-like effects in mice by an acute administration of NMDA receptor antagonist, MK-801 (0.1–0.6 mg/kg). An acute administration of MK-801 induced psychotic symptoms, manifested in the increase in locomotor activity (hyperactivity), measured in actimeters, as well as the memory impairment, assessed in the passive avoidance task. We revealed that an acute injection of CB1 receptor agonist, oleamide (5–20 mg/kg), had no influence on the short- and long-term memory-related disturbances, as well as on the hyperlocomotion in mice, provoking by an acute MK-801. In turn, an amnestic effects or hyperactivity induced by an acute MK-801 was attenuated by an acute administration of AM 251 (0.25–3 mg/kg), a CB1 receptor antagonist. The present findings confirm that endocannabinoid system is able to modify a variety of schizophrenia-like responses, including the cognitive disturbances and hyperlocomotion in mice. Antipsychotic-like effects induced by CB1 receptor antagonist, obtained in our research, confirm the potential effect of CB1 receptor blockade and could have important therapeutic implications on clinical settings, in the future.     

The Impact of CB2 Receptor Ligands on the MK-801-Induced Hyperactivity in Mice

It has been known that there is a relationship between cannabis use and schizophrenia-related symptoms; however, it can be a subject of controversy. The involvement of CB1 receptor ligands in the schizophrenia has already been revealed and confirmed. However, there is still lack of information concerning the role of CB2 receptors in the psychosis-like effects in mice and the further studies are needed.The aim of the present research was to study the role of the CB2 receptor ligands in the symptoms typical for schizophrenia. We provoked hyperlocomotion in mice which is analogous to positive psychosis-like effects in humans, by an acute administration of a NMDA receptor antagonist, MK-801 (0.3 and 0.6 mg/kg), a pharmacological model of schizophrenia. An acute administration of MK-801 induced the increase in locomotor activity (hyperactivity) in rodents, measured in actimeters.We revealed that an acute injection of CB2 receptor agonist JWH 133 at the dose range (0.05–1.0 mg/kg) and CB2 receptor antagonist, AM 630 at the dose range (0.1–1.0 mg/kg) decreased locomotion of mice. An acute injection of JWH 133 (2.0 mg/kg) and AM 630 (2.0 mg/kg) had no statistical significant influence on the locomotor activity of mice. However, an acute injection of both CB2 receptor ligands (agonist and antagonist), JWH 133, at the non-effective dose of 2.0 mg/kg and AM 630 at the non-effective dose of 2.0 mg/kg, potentiated the MK-801-induced hyperactivity.The present findings have confirmed that endocannabinoid system, not only via CB1, but also via CB2 receptors, may be involved in the schizophrenia-like responses, including hyperlocomotion in mice.     

Guanosine and GMP prevent seizures induced by quinolinic acid in mice

In the mammalian CNS, glutamate and GABA are the principal neurotransmitters mediating excitatory and inhibitory synaptic events, respectively, and have been implicated in the neurobiology of seizures. Guanine-based purines, including the nucleoside guanosine and the nucleotide GMP, have been shown to antagonize glutamatergic activity at the receptor level and the other purine nucleoside adenosine is a well-known modulator of seizure threshold. In the present study we investigated the anticonvulsant effect of i. p. guanosine and GMP against seizures induced by the glutamate agonist quinolinic acid (QA) or the GABA(A) antagonist picrotoxin in mice. Animals were pretreated with an i.p. injection of saline, guanosine or GMP 30 min before either an i.c.v. injection of 4 microliter QA (36.8 nmol) or a subcutaneous injection of picrotoxin (3.2 mg/kg). All animals pretreated with vehicle followed by QA or picrotoxin presented seizures, which were completely prevented by the NMDA antagonist MK-801 and the GABA agonist phenobarbital, respectively. Guanosine and GMP dose-dependently protected against QA-induced seizures, up to 70 and 80% at 7.5 mg/kg, with ED(50)=2. 6+/-0.4 and 1.7+/-0.6 mg/kg, respectively. Conversely, neither guanosine, GMP nor MK-801 affected picrotoxin-induced seizures, indicating some degree of specificity towards the glutamatergic system. This study suggests anticonvulsant properties of i.p. guanosine and GMP, which may be related with antagonism of glutamate receptors.     

D-Serine and a glycine transporter inhibitor improve MK-801-induced cognitive deficits in a novel object recognition test in rats

Compounds enhancing N-methyl-d-aspartate (NMDA) glutamate receptor function have been reported to improve cognitive deficits. Since cognitive deficits are considered to be the core symptom of schizophrenia, enhancing NMDA receptor function represents a promising approach to treating schizophrenia. In the present study, we investigated whether d-serine or a glycine transporter inhibitor N-[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine (NFPS), both of which enhance NMDA receptor function, could improve MK-801-induced cognitive deficits in rats, and compared their effects with those of the atypical antipsychotic clozapine and of the typical antipsychotic haloperidol. To assess cognitive function, we used a novel object recognition test in rats that measured spontaneous exploratory activity of a novel object when paired with a familiar object. We then evaluated the effects of the compounds on cognitive deficits induced by treatment with MK-801, the NMDA receptor antagonist. Pretreatment with clozapine (1, 5 mg/kg, i.p.) but not haloperidol (0.03, 0.1 mg/kg, i.p.) significantly improved MK-801-induced cognitive deficits. Pretreatment with D-serine at 800 mg/kg (i.p.) or NFPS (0.3, 1 mg/kg, i.p.) significantly improved MK-801-induced cognitive deficits under this test paradigm. These findings suggest that impaired preference for novel objects induced by MK-801 in the novel object recognition test could be a useful animal model for evaluating the efficacy of compounds targeting the cognitive deficits observed in schizophrenic patients. The results also suggest that enhancing NMDA receptor function is an effective way for treating the cognitive deficits associated with schizophrenia.     

Prior and delayed applications of dizocilpine or ethanol alter locomotor sensitization to morphine

Three experiments compared the effects of prior versus delayed applications of dizocilpine (MK-801), a noncompetitive NMDA antagonist, to ethanol, a putative NMDA antagonist, on morphine locomotor activity. In Experiment 1, rats received MK-801 (0.1 mg/kg), ethanol (1 g/kg), or vehicle injections 30 min prior to morphine (0 or 10 mg/kg) injections for 14 days. The expression of morphine (0 or 3 mg/kg) locomotor sensitization was assessed 1 week later. Both MK-801 and ethanol attenuated morphine-induced locomotor activity. Chronic MK-801 with or without morphine eliminated morphine's temporal pattern of activity calling into question the specificity of its effect on sensitization. In contrast, chronic ethanol administration attenuated morphine locomotor sensitization. In Experiment 2, the effects of the agents on the acute biphasic locomotor effects of morphine (hypoactivity followed by hyperactivity) were examined. Agents were administered 30 min prior to or 120 min after morphine (or vehicle). Neither agent at either administration time altered morphine's acute locomotor effects. In Experiment 3, the effects of chronic delayed application of MK-801 or ethanol (120-min post-morphine administration for 14 days) on the expression of morphine locomotor sensitization were assessed. Results were similar to the prior application effects of Experiment 1. These data suggest that the delayed effects of morphine are important in changes seen with chronic administration and these may involve NMDA receptor activation. Further, in conjunction with our previous work, ethanol appears to alter plasticity effects of chronic morphine administration perhaps via its NMDA antagonist effects.     

氟哌啶醇对MK-801致小鼠高活动性与前脉冲抑制损害的作用

目的观察氟哌啶醇对谷氨酸功能低下小鼠模型表现出的高活动性及前脉冲抑制(prepulse inhibition,PPI)损害的作用。方法昆明种小鼠152只分组(n=8或n=10)进行下述对照观察:观察不同剂量氟哌啶醇(0.03、0.1、0.3 mg/kg)腹腔注射对昆明种小鼠探究行为和自主活动的影响;以0.25 mg/kg MK-801诱导小鼠自主活动增加,观察上述剂量氟哌啶醇对MK-801致小鼠高活动性的影响;以0.5 mg/kg MK-801诱导小鼠PPI损害,观察氟哌啶醇(0.1、0.3、1 mg/kg)对基线水平PPI以及MK-801损害后PPI的作用。结果与对照组比较,氟哌啶醇剂量为0.1 mg/kg和0.3 mg/kg时,小鼠的探究行为及自主活动总路程减少(P<0.05);但剂量为0.03 mg/kg时,对小鼠的探究行为及自主活动均无影响(P>0.05)。氟哌啶醇剂量为0.1~0.3 mg/kg时,呈剂量依赖性抑制由MK-801引起的自主活动增加(F=27.23,P<0.01),0.1mg/kg的氟哌啶醇的抑制程度为22%(P<0.01),0.3 mg/kg的氟哌啶醇的抑制程度为65%(P<0.00...     

MK-801 prevents the development of behavioral sensitization during repeated morphine administration

Acute administration of morphine (10 mg/kg) to rats elicited an increase in locomotion that became sensitized upon repeated treatment over 14 days. Administration of the noncompetitive N-methyl-D-aspartate receptor (NMDA) antagonist MK-801 (0.1 or 0.25 mg/kg) prior to each morphine injection prevented the development of behavioral sensitization to morphine, an effect that persisted even after a 7-day withdrawal from repeated treatment. Sensitization was also prevented by coadministration of the competitive NMDA receptor antagonist CGS 19755 (10 mg/kg). In contrast, acute pretreatment with MK-801 did not alter the response of sensitized rats to morphine challenge, indicating that MK-801 does not prevent the expression of sensitization. When administered alone, MK-801 produced stereotyped movements at moderate doses (0.25 rng/kg) and horizontal locomotion at higher- doses, (0.5 mg/kg). Repeated administration of 0.25 mg/kg MK-801 elicited sensitization to its own locomotor stimulatory effects, such that this dose became capable of eliciting horizontal locomotion. Sensitization was not seen during repeated administration of 0.1 mg/kg MK-801 or 10 mg/kg CGS 19755, although both of these pretreatments did produce a sensitized response to subsequent challenge with 0.25 mg/kg MK-801. This effect was enhanced by coadministration of morphine, even though repeated administration of morphine alone failed to sensitize rats to MK-801 challenge. These results suggest a complex interplay between NMDA and opioid receptors, such that NMDA antagonists prevent morphine sensitization while morphine enhances the ability of NMDA antagonists to elicit sensitization to their own locomotor stimulatory effects. © 1994 Wiley-Liss, Inc.     

Dystonia induced by combined treatment with L-dopa and MK-801 in parkinsonian monkeys.

We examined whether the N-methyl-D-aspartate antagonist MK-801 (dizocilpine) would reverse parkinsonism or potentiate the effects of L-dopa in primates treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In contrast to its effect in rodent models, treatment with MK-801 (0.1 mg/kg) caused bradykinesia and ataxia in parkinsonian primates, but no locomotor stimulation. Coadministration of MK-801 (0.1 mg/kg) with L-dopa (20 mg/kg) induced marked dystonia accompanied by bradykinesia and ataxia. Dystonia was not induced by either treatment given alone. These findings indicate that MK-801 should not be advocated as an adjunct to dopamine agonist therapy in Parkinson's disease.     

Maturation of locomotor and Fos responses to the NMDA antagonists, PCP and MK-801

Antagonists at the N-methyl-D-aspartate (NMDA)-type glutamate receptor, such as phencyclidine (PCP) and dizocilpine (MK-801), are well-known to evoke increases in locomotor activity in adult rats and mice. However, little is known about the effects of NMDA antagonists on locomotor activity as a function of development. The present study examined locomotor responses to PCP or MK-801 in male rats of varying ages and found that prepubertal rats were more sensitive to the locomotor-elevating effects of PCP (1.5 mg/kg and 3. 0 mg/kg, s.c.) than were adults. Locomotor responses to MK-801 (0.1 and 0.2 mg/kg, s.c.) were not dependent on age. The age-dependent response to PCP may be related to developmental events in the motor cortex, since more Fos-immunoreactive neurons were observed in the motor cortex of prepubertal animals after PCP administration relative to adult animals. An opposite pattern of age-dependent Fos responses was observed in the posterior retrosplenial cortex. The results suggest that locomotor responses to NMDA antagonists can be influenced in an age- and drug-dependent manner and that maturational events in the motor cortex may modify responses to PCP.     

Clozapine improves dizocilpine-induced delayed alternation impairment in rats

Summary The effects of systemic administration of dizocilpine (0.16mg/kg, i.p.), clozapine (7.5mg/kg, s.c.) and coadministration of dizocilpine (0.16mg/ kg, i.p.) and clozapine (7.5mg/kg, s.c.) on acquisition of delayed alternation in a T-maze were tested in rats (N=7 per group) on six days with 10 choices per day and animal. Clozapine given alone did not impair delayed alternation learnint, except of the first day. Dizocilpine induced a significant delayed alternation impairment on all days tested. Pretreatment with clozapine significantly improved the dizocilpine-induced impairment. Treatment-induced changes of delayed alternation learning and of locomotor activities showed no correlation. The results demonstrate that clozapine functionally compensated for deficits induced by a blockade of the N-methyl-D-asparatate (NMDA) subtype of glutamate receptors.     

Chronic neonatal N-methyl-D-aspartate receptor blockade induces learning deficits and transient hypoactivity in young rats

A blockade of N-methyl-D-aspartate (NMDA)-type of glutamate receptor in rodents is believed to provide a pharmacological model of schizophrenia-related psychosis. Since neurodevelopmental abnormality, at least partly, could contribute to the pathogenesis of schizophrenia, the aim of this study was to recapitulate cognitive impairments accompanying this disorder in rats by a chronic neonatal treatment with a noncompetitive NMDA antagonist MK-801. Rat pups were treated with a low dose of MK-801 (0.05 mg/kg s.c.) chronically from early postnatal period (PD 7-49) known to be critical for glutamatergic system maturation. Locomotor activity in the "open-field" test, anxiety level in the elevated plus-maze test, and learning capacity in food rewarded spatial task were examined in young animals. Chronic MK-801 treatment produced a decrease of spontaneous motor and exploratory activity in 16- to 28-day-old rats. At the same time, a hyperlocomotion in response to acute administration of MK-801 was observed as well. Spatial learning of MK-801-treated rats was found to be negatively affected. Treated rats were able to respond to stress stimuli in the adequate manner but their anxiety level was found to be lower than in controls. Behavioral disturbances appeared to be temporary, and no such abnormalities could be detected at the age of 16 weeks. Thus, even mild chronic neonatal blockade of NMDA receptors may lead to a specific pattern of cognitive abnormalities presumably resulting from impairments of sensory information processing at the cortical-basal ganglia level.