实验性自身免疫性脑脊髓炎动物模型早期轴索损伤

目的 研究实验性自身免疫性脑脊髓炎(EAE)动物模型发病早期的轴索损伤.方法 采用髓鞘蛋白脂蛋白(PLP139-151)多肽作为抗原诱发EAE小鼠模型.小鼠经免疫后每天进行神经功能评分及称体质量,于发病后剥离脑及脊髓组织进行病理学研究.结果 7只(23.3%)小鼠于免疫后15～22 d内发病,平均免疫后发病时间为(19.00±2.58)d,平均神经功能评分为(2.14±0.69)分.免疫前小鼠平均体质量[(21.85±0.94)g]与发病后体质量[(23.24±1.55)g]比较差异无统计学意义.HE染色可见发病小鼠软脊膜下脊髓组织炎性细胞浸润明显,以小血管周围为主的血管袖套形成.病变累及脊髓多见,且较大脑病变重.LFB染色可见炎细胞浸润处髓鞘有不同程度脱失,同时Bodian银染可见轴索肿胀、横断.免疫组织化学染色可见髓鞘碱性蛋白着色的相同区域淀粉样前体蛋白浓染,而星形胶质细胞GFAP染色增生不明显.结论 PLP多肽诱发SJL/J小鼠的EAE模型临床症状较轻,病变主要累及脊髓,而在大脑未发现与MS类似的典型病灶.在EAE发病早期,髓鞘还未明显脱失时即可见轴索损伤,且早期轴索损伤与临床症状并不平行.     

PLP不同肽段诱导EAE模型的对比研究

目的建立不仅与多发性硬化(multiple sclerosis，MS)临床表现、病理特征接近而且病程相似的较为理想的复发一缓解型实验性自身免疫性脑脊髓炎(experimental autoimmune encephalomyelitis，EAE)模型。方法应用髓鞘蛋白脂质蛋白(proteolipid potein，PLP)多肽的两种免疫优势表位肽段PLP139-151和PLP178-191免疫雌性SJL／J小鼠，制作复发缓解型EAE(relapse remitting experimental autoimmune encephalomyelitis，RR—EAE)模型，观察其体重及神经功能评分的变化，应用HE、Luxol fas tblue髓鞘染色等方法观察模型的组织形态学改变。结果两种PLP肽段免疫的小鼠发病均具有缓解一复发的特点，出现明显的神经系统体征；小鼠发病时脑和脊髓组织显示明显的血管鞘形成、卫星现象和炎性细胞浸润以及脱髓鞘改变。结论PLP两种肽段均可诱发RR-EAE模型，这与临床MS的缓解一复发病程更相似，更能表现MS的临床特点，是研究MS的较为理想的动物模型。     

清开灵有效治疗实验性自身免疫性脑脊髓炎

目的　研究清开灵治疗实验性自身免疫性脑脊髓炎 ( EAE)的可能性及有效性。方法　应用蛋白脂质蛋白1 39- 1 51 ( PLP1 39- 1 51 )免疫 SJL/ J小鼠诱发慢性复发 -缓解性 EAE模型 ,研究清开灵对 PLP1 39- 1 51 诱导的小鼠淋巴结细胞增殖反应及 γ-干扰素 ( IFN-γ)分泌的作用 ,并通过神经功能评分观察清开灵治疗 EAE的有效性。结果　清开灵可抑制 PLP1 39- 1 51 诱导的淋巴结细胞增殖反应及 IFN-γ的分泌 ( P <0 .0 0 1 ) ,有效改善 EAE小鼠神经功能评分 ( P <0 .0 1 ) ,使发病时间延迟 ( P <0 .0 1 )。EAE小鼠发病数和死亡数较对照组减少 ,但其差异并无显著性 ( P>0 .0 5 )。结论　清开灵可有效治疗 EAE,为清开灵用于临床治疗多发性硬化提供了实验依据。     

髓鞘蛋白脂质蛋白多肽139—151诱发实验性自身免疫性脑脊髓炎小鼠模型

目的 用髓鞘蛋白脂质蛋白多肽（PLP）139-151诱发实验性自身免疫性脑脊髓炎（EAE）小鼠模型。方法 应用PLP139－151抗原加完全福（氏）佐剂免疫SWXJ小鼠。结果 免疫14－20d后小鼠即发病,发病率为80％,而且多数呈缓解－复发型。病理学证实发病小鼠脑和脊髓内具有典型的脱髓鞘改变和炎性细胞浸润。结论 以PLP139－151为抗原免疫SWXJ小鼠诱发EAE,具有模型稳定、发病率高和缓解－复发的特点,是研究多发性硬化较理想的动物模型。     

黄芩甙治疗实验性自身免疫性脑脊髓炎的实验研究

目的研究黄芩甙治疗实验性自身免疫性脑脊髓炎(EAE)的可能性及有效性。方法应用髓鞘脂质蛋白(PLP)139-151免疫SJL/J小鼠诱发慢性复发-缓解型EAE模型,研究黄芩甙对PLP139-151诱导的小鼠淋巴结细胞增殖反应及干扰素-γ(IFN-γ)、白介素-4(IL-4)分泌的作用,使用流式细胞技术检测黄芩甙对EAE小鼠淋巴结细胞CCR5表达的影响;通过神经功能评分观察黄芩甙治疗EAE的有效性。结果黄芩甙可抑制PLP139-151诱导的淋巴结细胞增殖反应及IFN-γ的分泌,提高IL-4的分泌(P<0.001),有效降低EAE小鼠淋巴结细胞CCR5的表达;显著改善EAE小鼠神经功能评分(P<0.01),使发病时间延迟(P<0.01)。EAE小鼠发病数和死亡数较对照组减少,但差异并无统计学意义(P>0.05)。结论黄芩甙可有效治疗EAE,为黄芩甙用于临床多发性硬化的治疗提供了实验依据。     

小胶质细胞在PLP_(139-151)诱导SJL小鼠EAE模型中的作用研究

目的观察髓鞘蛋白脂质蛋白139-151(proteolipid protein,PLP_(139-151))诱导SJL小鼠构建的复发缓解型的实验性自身免疫性脑脊髓炎(experimental autoimmune encephalomyelitis,EAE)模型复发期脑内小胶质细胞的病理改变。方法应用100μg、150μg PLP_(139-151)多肽片段免疫SJL小鼠构建复发缓解型EAE模型(分别简称为100μg PLP组、150μg PLP组),另设健康对照组(对照组;采用与实验组等体积溶媒处理),观察35 d。观察两组EAE小鼠的发病情况及神经功能残疾进展评分差异,选择发病快、神经功能残疾进展评分高者(计为EAE组)观察复发期小胶质细胞活化情况。EAE组于复发期疾病高峰时,对照组于相同时间点,取小鼠大脑皮层组织,应用免疫组织化学(immunohistochemical,IHC)染色及免疫荧光(immunofluorescence,IF)染色比较两组小胶质细胞的活化情况。结果 150μg PLP组小鼠在两个发病高峰(分别为免疫第13、28天)均早于100μg PLP组(分别为免疫第15天、31天),神经功能评分第2次发病高峰高于100μg PLP组(3.00±0.79 vs. 1.75±0.90,t=2.33,P0.05),第1次发病高峰与100μg PLP组差异无统计学意义(P0.05),故选择150μg PLP组(计作EAE组)观察复发期(免疫后第28天)小胶质细胞活性。与对照组相比,EAE组小鼠复发期大脑皮层中小胶质细胞的活化明显增多,组织染色上表现为Iba-1表达增高,细胞体积增大,细胞突起增多。结论 150μg PLP_(139-151)多肽片段免疫SJL小鼠构建的复发缓解型EAE模型复发期小鼠大脑皮层小胶质细胞明显活化。     

实验性自身免疫性脑脊髓炎小鼠的磁共振研究

目的研究动物模型实验性自身免疫性脑脊髓炎(experimental autoimmune encephalomyelitis,EAE)小 鼠中枢神经系统的MR表现。方法使用PLP139-151免疫接种雌性SJL／J小鼠诱导EAE。分别取复发期和缓解期 的EAE小鼠行脑和脊髓常规MR及Gd—DTPA增强MR扫描,并做组织病理学检查。结果PLP139-151能较好的诱 导出慢性复发-缓解型EAE模型,Gd-DTPA增强MR检查能充分显示血脑屏障的破坏,反映脑和脊髓的病灶,而且 显示的病灶相对信号强度复发期明显高于缓解期,在病灶处均可见炎症细胞浸润,髓鞘脱失,病灶周围或远离病灶 处炎症反应轻微。结论Gd—DTPA增强MR检查能准确反映血脑屏障的破坏,病变累及部位及病变程度,为今后使 用药物干预EAE判断疗效、指导进行较准确的病变部位取材时提供了一种更为客观的手段。     

MOG35-55诱发实验性自身免疫性脑脊髓炎小鼠模型

目的建立髓鞘少突胶质细胞糖蛋白35-55(MOG35-55)多肽诱发的实验性自身免疫性脑脊髓炎(EAE)小鼠模型。方法应用MOG35-55多肽加福氏完全佐剂皮下注射免疫C57BL/6小鼠,观察其临床症状及病理改变。结果EAE组发病率100%,发病时间为免疫后(16.1±3.9)d,呈慢性单相病程;HE染色见EAE组大脑、小脑、脑干及脊髓组织中大量单个核细胞浸润,血管周围形成炎细胞袖套,白质区明显;Luxolfastblue染色见EAE组脊髓白质脱髓鞘改变;雌、雄小鼠在发病率、发病时间、发病程度及病理改变上均无明显差别。结论本研究以MOG35-55多肽为抗原成功诱发EAE模型,该模型发病率高,病理接近多发性硬化(MS),是研究MS的极为理想的动物模型。     

载脂蛋白E拟肽对实验性变态反应性脑脊髓炎小鼠基质金属蛋白酶-9和基质金属蛋白酶组织抑制因子-1表达的影响

目的探讨载脂蛋白E(Apo E)拟肽对实验性变态反应性脑脊髓炎(EAE)小鼠基质金属蛋白酶-9(MMP-9)和基质金属蛋白酶组织抑制因子-1(TIMP-1)表达的影响。方法将30只雌性C57BL/6J小鼠随机分为Apo E拟肽组、EAE组和正常组,每组10只小鼠。EAE模型通过以髓鞘少突胶质细胞糖蛋白多肽35-55为抗原诱导。Apo E拟肽组在免疫后第2 d到30 d每隔2 d按5 mg/(kg·d)背部皮下注射Apo E拟肽。EAE组和正常组均以等体积生理盐水替代。免疫后第0~35 d每日对小鼠进行神经功能评分。免疫后第35d解剖小鼠,分离大脑和脊髓并行HE染色。采用免疫组化染色法检测各组小鼠大脑、脑干和脊髓的MMP-9和TIMP-1的表达。结果正常组小鼠均未发病。Apo E拟肽组、EAE组的小鼠全部发病,但各有1只小鼠发病后死亡。Apo E拟肽组与EAE组的发病潜伏期差异无统计学意义(P=0.72)。Apo E拟肽组的神经功能评分在峰值和慢性期(第35 d)均明显低于EAE组(均P0.05)。HE染色示,正常组未见炎症细胞浸润;EAE组小鼠大脑、脑干和脊髓均有不同程度的炎性细胞浸润,以脑干和脊髓较为明显;Apo E拟肽组小鼠CNS炎性细胞浸润相对于EAE组明显减少。EAE组小鼠大脑、脑干和脊髓的MMP-9表达均高于正常组(均P0.05)。Apo E拟肽组小鼠大脑和脊髓的MMP-9表达要明显低于EAE组(均P0.05),其中Apo E拟肽组小鼠中脑和脊髓的MMP-9表达与正常组相比无明显差异(均P0.05)。正常组小鼠脊髓TIMP-1的表达明显高于EAE组和Apo E拟肽组(均P0.05)。而Apo E拟肽组与EAE组小鼠大脑、脑干和脊髓TIMP-1表达的差异均无统计学意义(均P0.05)。结论 Apo E拟肽能通过抑制大脑和脊髓MMP-9的表达改善EAE小鼠的症状。     

日本血吸虫虫卵抗原对实验性脑脊髓炎的干预研究

目的利用日本血吸虫虫卵抗原(SEA)来干预实验性自身免疫性脑脊髓炎(EAE)小鼠模型,试图探讨寄生虫感染与EAE的关系。方法利用血吸虫虫卵抗原干预EAE小鼠,观察行为学和病理改变。同时取不同抗原刺激的淋巴结细胞培养,ELISA法测定上清IL-4、IFN-γ的含量。结果用SEA不同时间段干预EAE,发现可以减轻EAE的发病程度,但在延缓和阻止发病方面作用不明显,并在行为学和病理学上得到证实。而用SEA和PLP178-191体外刺激联合免疫后小鼠的淋巴结细胞,发现SEA刺激后可以升高IL-4,降低IFN-γ,而PLP178-191刺激则相反。在单用PLP178-191免疫和联合免疫相比较中,发现PLP178-191体外再刺激后联合免疫组细胞分泌IFN-γ降低,IL-4升高。结论SEA可以减轻EAE的发病程度。细胞因子在寄生虫感染影响EAE的发病中起了重要的作用,调节Th1/Th2平衡,纠正体内Th1偏移是寄生虫抗原能够调节EAE发病的原因之一。     

Phencyclidine and MK-801: a behavioral and neurochemical comparison of their interactions with dihydropyridine calcium antagonists

The impairment of rotarod ability and the convulsive activity of phencyclidine (PCP) and MK-801 were compared in male CD-1 mice. The putative interaction between nifedipine and PCP and MK-801 on these behavioral measurements was also quantitated and compared. MK-801 produced a dose dependent inhibition of rotarod ability with an ED50 of 0.5 mg/kg. Nifedipine potentiated the impairment of rotarod ability by MK-801. Both PCP and MK-801 produced convulsive behavior in mice which was characterized by jumping and wild running fits; the CD50 for MK-801 was 1.3 mg/kg. Nifedipine dose dependently inhibited the convulsions associated with MK-801 and PCP. PCP but not MK-801 increased [3H]nitrendipine binding to dihydropyridine (DHP) binding sites on mouse brain membranes. MK-801 blocked the effects of PCP on [3H]nitrendipine binding. These findings suggest that MK-801 is a potent PCP-like drug which interacts with nifedipine and neuronal DHP binding sites. Nifedipine's reduction of the hyperactivity and convulsions elicited by MK-801 may be of importance in the eventual development of MK-801 as an antiischaemic and anticonvulsant drug.     

Proteome analysis after co-administration of clozapine or haloperidol to MK-801-treated rats

Summary MK-801, a glutamergic, N-methyl-D-aspartate (NMDA)-receptor antagonist that mediates neurotransmission and has psychotomimetic properties, giving schizophrenia-like symptom. The objective of this study was to investigate the effects on the thalamic and cortical proteome of one typical (haloperidol) and one atypical (clozapine) antipsychotic drug in interaction with MK-801 in rats. Rats received subcutaneous injections of MK-801 or vehicle (controls) or MK-801 together with concurrent administration of haloperdol or clozapine for eight days. Protein samples from thalamus and cortex were analyzed with two-dimensional gel electrophoresis in combination with mass spectrometry. MK-801 induced alterations in the levels of three proteins in both cortex and thalamus. Clozapine reversed all the protein changes. Haloperidol reversed two. Both antipsychotics induced new protein changes in both cortex and thalamus not seen after MK-801-treatment by alone. In conclusion, the MK-801 animal model shows potential for investigation of different antipsychotic drugs and biochemical treatment effects in schizophrenia.     

The effects of N-methyl-D-aspartate receptor blockade with MK-801 upon the relationship between cerebral blood flow and glucose utilisation

The local cerebral circulatory and metabolic effects of MK-801, a selective non-competitive N-methyl-D-aspartate receptor antagonist have been examined in conscious rats with quantitative autoradiographic techniques using [14C]iodoantipyrine and [14C]2-deoxyglucose as tracers. Local cerebral blood flow (CBF) and local cerebral glucose utilisation (GU) were measured in 41 discrete neuroanatomical loci using identical criteria for region of interest localisation. Animals received either saline or MK-801 (0.5 mg/kg in saline) intravenously 10 min prior to the start of GU determination, or 15 min before the CBF measurement. MK-801 effects an immediate transient, elevation in mean arterial pressure (elevated by 30% from baseline) which returned rapidly to preinjection levels and a sustained moderate hypercapnia (arterial carbon dioxide tension increased by 16%) which persisted throughout the measurement periods. Statistically significant changes in GU were observed in 13 brain region structures after MK-801 administration. Glucose utilisation was significantly and markedly elevated with MK-801 in some limbic structures (particularly the hippocampus, posterior cingulate and entorhinal cortices), the inferior colliculus and most of the neocortex displayed moderate reductions in GU after MK-801 treatment. In the majority of brain regions (28 or the 41 studied), MK-801 minimally altered GU. There were widespread alterations in local CBF with MK-801 although in the majority of brain regions (24 of the 41 studied) there was no statistically significant alteration in CBF with MK-801. With one exception (the anterior thalamic nucleus), CBF was increased with MK-801 in all regions in which glucose use was elevated with the drug.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of the MK-801-induced appetitive extinction deficit with pressing for reward and associated pERK1/2 staining in prefrontal cortex and nucleus accumbens

Administration of the noncompetitive N-methyl-d-aspartate (NMDA)-receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801) has been shown to produce extinction deficits on appetitive operant tasks. The present study sought to further explore this by comparing extinction pressing to pressing for the primary reward and examining associated neural correlates to determine if the MK-801 extinction profile resembled the behavioral and neural profile associated with pressing for primary reward. Immunohistochemical labeling of phosphorylated extracellular signal-regulated kinase-1 and -2(pERK1/2) in the prelimbic (PrL) and infralimbic (IL) cortices and nucleus accumbens shell (AcbSh) and core (AcbC) was examined after rewarded or extinction lever pressing conditions. A dose-response curve revealed a within-day extinction deficit following administration of 0.05 mg/kg MK-801. All doses of MK-801 were associated with reduced IL pERK1/2 staining but only the 0.05 mg/kg dose was associated with elevated AcbSh pERK1/2 labeling. Extinction pressing under the influence of MK-801 was elevated compared to that seen during rewarded pressing—whether on MK-801 or saline. Rewarded pressing following saline or MK-801 was associated with elevated pERK1/2 in the PrL with no similar patterns in the MK-801/extinction group. There was more pERK1/2 labeling in the AcbSh of the MK-801 extinction group than any other condition. These data suggest that the MK-801-induced extinction deficit may be due to the combination of an underactive cortical behavioral inhibition system and an overactive AcbSh reward system.     

Electrophysiological effects of MK-801 on rat nigrostriatal and mesoaccumbal dopaminergic neurons

The electrophysiological effects of the non-competitive (NMDA) antagonist (+)-MK801 (MK-801) on nigrostriatal and mesoaccumbal dopaminergic (DA) neurons were evaluated in chloral hydrate-anesthetized rats. MK-801 (0.05–3.2 mg/kg, i.v.) stimulated the firing rates of 14 (74%) of 19 nigrostriatal DA (NSDA) neurons and all 16 mesoaccumbal DA (MADA) neurons tested. Stimulatory effects of the drug were more prominent on MADA neurons. Interspike interval analysis revealed that MK-801 also regularized DA neuronal firing pattern. Acute brain hemitransection between the midbrain and forebrain attenuated the stimulatory effects of MK-801 on firing rate and blocked the effects on firing pattern. Similar to MK-801, hemitransection itself increased NSDA and MADA cell firing rates and regularized firing pattern. Both i.v. and iontophoretic MK-801 blocked the excitatory effects of iontophoretic NMDA but did not effect excitations caused by the non-NMDA glutamatergic receptor agonists quisqualate and kainate. Iontophoretic MK-801 had no effect alone. These results suggest that the excitatory effects of i.v. MK-801 on DA neuronal activity are not due to direct actions on DA neurons. Glutamatergic projections originating anterior to the hemistransection appear to play a role in the effectrs of MK-801 on DA neuronal activity.     

Antiepileptic Effects of MK-801, a Noncompetitive NMDA-Receptor Antagonist, in the Low-Frequency Kindling Model of Epilepsy

Abstract: We assessed the acute effect of MK-801 (0.05–0.7 mg/kg), a noncompetitive NMDA-receptor antagonist, on hippocampus-kindled seizures induced with low-frequency (2 Hz) electrical stimulations. MK-801 dose-dependently increased the seizure threshold (PNT, the number of stimulating pulses required for the triggering of epileptic dterdischarge), whereas most of the previous studies which assessed the effect of MK-801 on kindled seizures could not detect the elevation of seizure threshold by MK-801. In addition MK-801 decreased the severity of induced seizures at low doses at which previous studies could not detect the antiepileptic effect of MK-801, suggesting that the low-frequency kindling technique might be a more sensitive and reliable model of epilepsy than the conventional high-frequency kindling technique.     

Sex differences in the inhibitory effects of the NMDA antagonist, MK-801, on morphine and stress-induced analgesia

We examined the effects of intraperitoneal administrations of the noncompetitive NMDA receptor antagonist, (+) MK-801, its inactive enantiomer, (-) MK-801, and the prototypic opiate antagonist, naloxone, on restraint- and morphine-induced analgesia in male and female deer mice, Peromyscus maniculatus. Both restraint (30 min) and morphine (1.0 mg/kg) induced significant analgesic responses with male mice displaying significantly greater levels of opioid-induced analgesia than female animals. These analgesic responses were completely blocked by, naloxone (1.0 mg/kg), significantly reduced by (+) MK-801 (0.25 mg/kg) and unaffected by (-) MK-801 (0.25 mg/kg) pretreatments. There were significant male-female differences in the inhibitory effects of (+) MK-801; the higher levels of morphine- and restraint-induced analgesia of the males were completely blocked, while the lower level analgesic responses of the females were significantly reduced, but not blocked, by (+) MK-801. These observations provide further evidence that NMDA receptors are involved in the mediation of endogenous and exogenous opioid analgesia and show that there are significant male-female differences in the inhibitory effects of (+) MK-801 on opioid-mediated analgesia.     

Effects of MK-801 and electroconvulsive shock on c-Fos expression in the rat hippocampus and frontal cortex

Both the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 and electroconvulsive shock (ECS) have been reported to induce c-Fos in rat brain. However, the former has anticonvulsant and psychotomimetic effects and the latter has proconvulsant and antipsychotic effects. To understand the mode of action of these treatments, the authors examined the effect of MK-801 and the interaction between MK-801 and ECS on the induction of c-Fos in the rat hippocampus and frontal cortex. MK-801 induced c-Fos in these brain regions in a nonlinear dose-response relationship. Maximum effect was achieved with 1-2 mg/kg of MK-801. The level of c-Fos paralleled animal hyperkinetic behavior, suggesting the role of c-Fos in the induced psychotomimetic behaviors. Pretreatment with MK-801 dose-dependently attenuated both the seizures and c-Fos expression by ECS. However, at an MK-801 pretreatment dose of 8 mg/kg, which completely blocked ECS-induced seizure, the induction of c-Fos was not completely blocked, suggesting non-NMDA mediated pathways of the induction of c-Fos by ECS.     

AMPA receptor antagonism attenuates MK-801-induced hypermetabolism in the posterior cingulate cortex

The effect of pretreatment with an AMPA receptor antagonist, NBQX, on MK-801-induced alterations in glucose use was examined using [¹⁴C]-2-deoxyglucose autoradiography. NBQX (7 mg/kg) had minimal effect on glucose utilisation in all anatomical regions examined. The intravenous administration of MK-801 (0.2 mg/kg) induced increases in glucose use in the limbic system and cingulate cortex. MK-801 reduced glucose utilisation in the sensory motor and auditory cortices. Pretreatment with NBQX attenuated the MK-801-induced hypermetabolism in the posterior cingulate cortex. The decreases in glucose utilisation induced by MK-801 were not exacerbated by the pretreatment with NBQX. The interaction between NBQX and MK-801 suggests a possible method of attenuating some of the adverse effects of the non-competitive NMDA receptor antagonists in the posterior cingulate cortex.     

Antidepressant drugs increase the locomotor hyperactivity induced by MK-801 in rats

Summary MK-801, a non-competitive NMDA receptor antagonist, induced the locomotor hyperactivity in rats. Imipramine (IMI), amitriptyline (AMI), citalopram (CIT) given acutely increased the MK-801-induced locomotor hyperactivity. Mianserin (MIA) showed a similar but weaker effect. Haloperidol completely blocked the hyperactivity induced by the antidepressant drug (AD) + MK-801. Prazosin had an only weak antagonistic effect. Repeated treatment with AD increased the MK-801 locomotor hyperactivity to a greater extent than acute treatment. This effect was completely blocked by haloperidol and only partly by prazosin.The obtained results indicate that the dopamine system may be involved, at least in part, in the potentiating effect of the combined treatment with AD + MK-801.