Memory performance and scopolamine: Hypoactivity of the thalamus revealed by cytochrome oxidase histochemistry

Spatial memory learning is related to the functioning of a neuronal circuit composed of cortical, hippocampal and diencephalic brain regions. The Morris water maze (MWM) is frequently used to assess spatial memory in rats. In this study, the neuronal functional activity of some brain limbic system regions after a memory task in adult male Wistar rats injected with scopolamine (1.0 mg/kg, i.p.) was assessed using cytochrome oxidase (COx) histochemistry. The rats were trained following a working memory schedule in the MWM. A trained group injected with saline and an untreated control group were examined to compare changes in COx activity in the dorsal hippocampus, anterior thalamus, mammillary nuclei, prefrontal cortex and ventral tegmental area. The scopolamine-treated group showed an impairment of spatial learning. Also, a decrease in COx activity was found in this group as compared to the saline group in the anteroventral and anteromedial thalamic nuclei. Overall, these findings suggest that memory deficits induced by scopolamine may be due to impairment of the cholinergic function in the anterior thalamic nuclei.     

慢性间歇低氧对幼鼠认知及相关脑区CREB的影响

目的:观察慢性间歇低氧(CIH)对幼鼠认知的影响并探讨其潜在的机制。方法:取八臂迷宫训练成功的SPF级健康雄性SD幼鼠40只,随机分为:间歇低氧2周(2IH)、4周组(4IH),对照2周(2C)、4周组(4C),建立IH幼鼠模型,低氧结束后进行八臂迷宫测试,观察海马和前额叶皮层超微结构变化及cAMP反应元件结合蛋白(CREB)mRNA和磷酸化CREB蛋白的表达。结果:4组幼鼠的记忆错误次数比较均有显著差别(均P0.05);IH各组海马及前额叶皮层神经元均出现早期凋亡和变性,尤以4IH组最为明显,对照组则基本正常;与相应对照组相比,2IH、4IH组幼鼠海马和前额叶皮层CREB mRNA和p-CREB蛋白的表达水平显著降低(均P0.05),且以4IH组最低(均P0.01),差异显著,两对照组之间无显著差异(P0.05)。结论:慢性间歇低氧诱导海马和前额叶皮层神经元超微结构改变,还下调CREB的基因转录和抑制CREB蛋白磷酸化,抑制记忆相关蛋白的合成,这可能是引起学习记忆能力下降的重要机制之一。     

PTSD大鼠海马CA1区和前额叶皮层突触小泡蛋白的表达

目的:观察创伤后应激障碍(posttraumatic stress disorder,PTSD)大鼠海马CA1区和前额叶皮层(prefrontal cortex,PFC)突触小泡蛋白(synaptophysin)的表达,探讨PTSD大鼠空间记忆损伤的机制。方法:健康成年SD大鼠36只,随机分为正常对照组和模型组,每组18只。模型组采用单次延长应激(single prolonged stress,SPS)构建PTSD大鼠模型。Morris水迷宫实验检测2组大鼠的学习记忆能力,利用免疫组化、Western blot和免疫荧光实验检测海马CA1区和PFC突触小泡蛋白的表达情况。结果:经过Morris水迷宫实验,模型组大鼠从第2天开始逃避平台的潜伏期较对照组均显著延长(P 0.01),目标象限的停留时间均明显降低(P 0.01),穿越原平台位置的次数也明显减少(P 0.01)。在免疫组化、Western blot和免疫荧光实验中,模型组大鼠海马CA1区和PFC突触小泡蛋白的表达较对照组均明显减少(P 0.05或P 0.01)。结论:创伤后应激障碍大鼠空间记忆能力减退,可能与海马CA1区和PFC突触小泡蛋白的表达减少有关。     

c-Fos expression in supramammillary and medial mammillary nuclei following spatial reference and working memory tasks

To investigate brain substrates of spatial memory, neuronal expression of c-Fos protein was studied. Two groups of rats were trained in two spatial memory tasks in the Morris water maze, where the rats have to apply a reference memory rule or a working memory rule. In addition to the experimental groups, two control groups were used to study c-fos activation not specific to the memory processes studied. After immunohistochemical procedures, the number of c-Fos positive neuronal nuclei was quantified in the mammillary body (MB) region (medial mammillary nucleus [MMn] and supramammillary nucleus [SuM]). The results have shown that some MMn neurons expressed c-Fos nuclear immunoreactivity related to spatial working memory but not to spatial reference memory. The increased number of c-Fos immunoreactive neuronal nuclei in the SuM was related to spatial training but not to either working or reference memory demands of the tasks.     

Disinhibition of the prefrontal cortex leads to brain-wide increases in neuronal activation that are modified by spatial learning

Deficient prefrontal cortex (PFC) GABA function is hypothesized to play a role in schizophrenia and other psychiatric disorders. In rodents, PFC GABA_A receptor antagonism produces cognitive and behavioral changes relevant to these disorders, including impaired spatial memory assessed with the traditional working/reference memory radial maze task. This aspect of spatial memory does not depend on PFC, suggesting that deficient PFC GABAergic transmission may interfere with non-PFC-dependent cognitive functions via aberrant increases in PFC output. To test this, we assessed whether PFC GABA_A antagonism (50 ng bicuculline methbromide) alters neuronal activation in PFC terminal regions, including the striatum, thalamus, hippocampus, amygdala, and cortical regions, of adult male rats using the immediate early gene, c-Fos, as an activity marker. A subset of these animals were also trained and/or tested on the working/reference memory radial maze task. These treatments caused widespread increases in neuronal activation in animals under baseline conditions, with notable exception of the hippocampus. Furthermore, PFC GABA_A antagonism impaired task performance. In most instances, training and/or testing on the radial maze had no additional effects on neuronal activation. However, in both the hippocampus and rhomboid thalamic nucleus, PFC GABA_A antagonism caused a selective increase in neuronal activation in animals trained on the maze. These results indicate that deficiencies in PFC GABAergic transmission may have widespread impacts on neuronal activity that may interfere with certain PFC-independent cognitive functions. Furthermore, these alterations in activity are modulated by plasticity induced by spatial learning in the hippocampus and rhomboid thalamic nucleus.

     

Cholinesterase inhibitors ameliorate spatial learning deficits in rats following hypobaric hypoxia

Cognitive functions especially learning and memory are severely affected by high altitude (HA) exposure. Hypobaric hypoxia (HBH) encountered at HA is known to cause oxidative stress, alterations of neurotransmitters and cognitive impairment. We hypothesized that alteration in cholinergic system may be involved in HBH-induced learning impairment. The present study has investigated the cholinergic dysfunctions associated with simulated HBH-induced impairment of learning in rats and protective role of acetylcholine esterase inhibitors (AChEIs). Male Sprague–Dawley rats were exposed to HBH equivalent to 6,100 m for 7 days in a simulated decompression chamber. After stipulated period of exposure, learning ability was assessed using Morris water maze (MWM) task. Cholinergic markers like acetylcholine (ACh) and acetyl cholinesterase (AChE) were evaluated from cortex and hippocampus. Morphological changes were evaluated from cortex, CA1, and CA3 region of hippocampus by Nissle staining and by electron microscopy. We found that exposure to HBH led to impairment of learning ability in MWM task, and it was accompanied by decrease in ACh level, increase in AChE activity, and revealed critical cellular damage. Administration of AChEIs like physostigmine (PHY) and galantamine (GAL) resulted in amelioration of the deleterious effects induced by HBH. The AChEIs were also able to restore the neuronal morphology. Our data suggest that cholinergic system is affected by HBH, and AChEIs were able to improve HBH-induced learning impairment in rats.     

慢性不完全性睡眠剥夺对幼鼠学习记忆的影响

目的：探讨慢性不完全性睡眠剥夺对幼鼠学习记忆能力的影响及其可能机制。方法：建立慢性不完全性睡眠剥夺动物模型，并测定其空间学习记忆能力，同时对幼鼠大脑前额皮质及海马神经元性一氧化氮合酶(nNOS)的表达进行分析。结果：睡眠剥夺组幼鼠完成预定任务所需的时间及发生错误的次数均超过正常对照组。睡眠剥夺组的nNOS在前额皮质区域阳性、强阳性表达面积及在海马区域强阳性表达面积均大于正常对照组。结论：慢性不完全性睡眠剥夺会影响幼鼠的学习记忆能力，而前额皮质及海马中nNOS表达水平的下降可能是慢性不完全性睡眠剥夺影响未成熟脑学习记忆能力的机制之一。     

Differential roles of dorsal hippocampal subregions in spatial working memory with short versus intermediate delay

In order to determine the role of subregions of the hippocampus in spatial working memory, this study combined selective neurotoxic lesions of the hippocampal subregions with a simple delayed nonmatching-to-place task on a radial maze in rats. Lesions of the dentate gyrus or the CA3, but not the CA1, subregion of the hippocampus induced a deficit in the acquisition of the task with short-term delays (i.e., 10 sec) and impaired performance of the task in a novel environment. All subregional lesions produced sustained impairment in performing the task with intermediate-term delays (i.e., 5 min) when rats were tested in a familiar environment. The results suggest a dynamic interaction among the dorsal hippocampal subregions in processing spatial working memory, with the time window (i.e., delay) of a task recognized as an essential controlling factor.     

Effect of reversible inactivation of locus ceruleus on spatial reference and working memory

The locus coeruleus (LC) is the largest source of norepinephrine (NE) in the prefrontal cortex and the hippocampus, influencing the cognitive functions of these areas. All previous studies have studied the role of the LC–NE system on learning and memory using the irreversible lesion technique, employing either electrocoagulation or excitotoxins. However, the reversible functional inactivation of LC by means of stereotaxic local microinjection of lidocaine could measure the phases of memory processing (acquisition, consolidation and retention) without any interference with the other cognitive functions of the same structure either during earlier or later phases of the same process. The aim of this study is to investigate LC involvement in spatial reference and working memory by inducing bilateral pre-training, post-training and pre-retrieval lidocaine functional inactivation using the Morris water maze task. The reversible inactivation of LC was applied at different stages of spatial memory formation: (1) immediately before the training sessions to determine the effects on acquisition of the both reference and working memory; (2) immediately after the training session to evaluate effects on both spatial memory consolidation and retention of working memory; and (3) immediately before the 24 h retention session to analyze the effects on the retrieval process of reference memory. Our results indicate that the bilateral reversible inactivation of LC significantly impaired the acquisition of reference and working memory, while it had no effect on consolidation and/or retention of such memories in the Morris water maze (MWM) task. Therefore, the noradrenergic system of the LC may play a more important role in acquisition than in consolidation and retrieval of spatial memory in wistar rats.     

海马CA1区5-HT_(1A)受体调控PTSD大鼠空间记忆的作用

目的:观察创伤后应激障碍(PTSD)大鼠海马长时程增强(LTP)的变化以及5-羟色胺1A受体(5-HT_(1A)受体)和突触后致密物蛋白95(PSD-95)的表达,探讨5-HT_(1A)受体调控PTSD大鼠空间记忆的机制。方法:健康成年SD大鼠36只,随机分为正常对照组和模型组,每组18只。模型组采用连续单一刺激构建PTSD大鼠模型。Morris水迷宫实验检测2组大鼠的学习和记忆能力,电生理实验检测强直性高频刺激对海马LTP的影响Western blot法和免疫荧光实验检测海马5-HT_(1A)受体和PSD-95蛋白的表达。结果:Morris水迷宫实验结果显示在各实验日模型组大鼠逃避平台的潜伏期较对照组显著延长(P0.05)。电生理实验结果显示在强直性高频刺激后,2组大鼠海马诱发电位的幅值明显升高,模型组诱发电位的幅值显著低于对照组(P0.01)。Westem blot实验和免疫荧光实验结果显示,与对照组比较,模型组大鼠海马CA1区5-HT_(1A)受体的表达显著增加(P0.05),但PSD-95的表达明显减少(P0.05)。结论:PTSD大鼠空间记忆能力减退,可能与海马CA1区5-HT_(1A)受体的表达增加和PSD-95的表达减少有关。     

血管性痴呆大鼠记忆障碍与海马神经型一氧化氮合酶表达的关系

目的：探讨NO参与血管性痴呆大鼠学习记忆障碍的作用机制。方法：要用4－血管阻断的方法建立大鼠血管性痴呆模型,以免疫组化法检测海马神经型一氧化氮合酶蛋白表达的变化;以Nissl染色方法,结合图象分析统计海马神经元丢失比率,同时采用Y－型迷宫,进行行为学检测,定量测定其学习记忆成绩,结果：在血管性痴呆大鼠空间分辨学习记忆能力发生严重障碍时,海马CA1区神经元丢失比率较正常对照组增高,神经型一氧化氮合酶蛋白表达增加。结论：神经型一氧化氮合酶可能引起海马CA1区神经元凋亡或坏死增加,海马神经元受损,导致血管性痴呆大鼠学习记忆障碍。     

长时间应用L-精氨酸增强大鼠学习记忆功能和大脑皮质、海马nNOS或c-fos的表达及神经元数目的增加(英文)

为探讨长时间应用一氧化氮(NO)对学习记忆功能和神经系统可塑性的影响,以及NO与c-fos基因表达的关系,分别给初断乳的大鼠灌胃NO前体左旋-精氨酸(L-Arg)或一氧化氮合酶抑制剂L-NAME,用Morris水迷宫检测大鼠的学习记忆功能,用免疫组化技术和HE染色检测大脑皮质和海马CA1、CA3、DG区的神经元型一氧化氮合酶(nNOS)和c-fos基因的表达以及神经细胞数目的变化。将大鼠随机分成L-Arg组、L-NAME组和对照组。大鼠断乳后分别每天用L-Arg[200mg/(kg.d)]、L-NAME[50mg/(kg.d)]和等剂量的蒸馏水灌胃,持续3个月。结果显示:长期应用NO前体L-Arg可明显缩短大鼠的寻台潜伏期,促进nNOS和c-fos基因的表达,同时大脑皮质和海马CA1、CA3、DG区的神经元数目增加;而长期应用一氧化氮合酶抑制剂L-NAME可抑制大鼠寻台潜伏期的缩短和nNOS、c-fos基因的表达,同时大脑皮质和海马CA1、CA3、DG区的神经元数目减少。因此我们认为长时间应用NO可促进神经系统c-fos基因的表达和幼鼠神经系统的发育,即可塑性的变化,继而影响大鼠的学习记忆功能。     

The effects of NMDA lesions centered on the postrhinal cortex on spatial memory tasks in the rat

Rats with bilateral N-methyl-D-aspartate lesions centered on the postrhinal cortex (POR) and sham lesions were tested in a series of spatial memory tasks. The POR-lesioned rats were significantly impaired compared with sham rats in the reference memory version of both the water maze and radial arm maze tasks and in the standard radial arm maze working memory task. The POR-lesioned rats displayed a delay-independent impairment in the working memory versions of the water maze and in a delayed nonmatching-to-place (DNMP) version of the radial arm maze task. The POR-lesioned rats were also impaired in a DNMP procedure conducted in the T-maze. These findings indicate that the POR has a delay-independent role in the processing of spatial information.     

Diverse Sensitivity of RHA/Verh and RLA/Verh Rats to Emotional and Spatial Aspects of a Novel Environment as a Result of a Distinct Pattern of Neuronal Activation in the Fear/Anxiety Circuit

Psychogenetically selected Roman high (RHA/Verh) and Roman low (RLA/Verh) avoidance rats constitute a well-recognized model of diverse emotional reactivity. The two Swiss lines display marked behavioral and endocrine differences in reaction to a novel environment. In our study we found that these differences are accompanied by a distinct, line-specific pattern of neuronal activation within the fear/anxiety circuit. We have compared the c-Fos protein expression in the medial prefrontal cortex (mPFC), basolateral (BLA), central (CeA), medial (MeA), and cortical (CoA) nuclei of amygdala, paraventricular nucleus of the hypothalamus (PVN), and CA1, CA2, and CA3 fields of the hippocampus upon exposure to a novel situation of different stressorgeneity (open field with illuminated center, elevated plus maze, hole board test and acute restraint). Profound between-line differences in the sensitivity to emotional and spatial aspects of the behavioral challenge were observed for tests measuring spontaneous behavior. This effect seems to reflect different motivational factors driving the rat behavior, which clearly suggests that the diverse emotional reactivity of RHA/Verh and RLA/Verh rats is a result of different activation of the fear/anxiety circuit. Edited by Stephen Maxson.     

黄芩茎叶黄酮抑制冈田酸引起大鼠脑内PHF异常生成和蛋白磷酸酶的调节机制

目的:探讨黄芩茎叶黄酮(SSF)对冈田酸(OA)引起的大鼠脑内双螺旋细丝(PHF)异常生成的抑制作用及其对蛋白磷酸酶(PP)的调节机制。方法:雄性SD大鼠,采用侧脑室注射OA(200 ng/kg)建立记忆障碍模型,Morris水迷宫进行记忆障碍模型筛选,取造模成功大鼠每日分别灌胃25、50和100 mg/kg SSF,连续36 d。Western blot法测定大鼠皮层与海马组织中PHF、PP1、PP2A-Cα、PP2A-Cβ、PP2CA和PP2CB的蛋白表达,以银杏叶黄酮作为阳性对照药。结果:与假手术组大鼠相比,模型组大鼠皮层与海马中PHF的蛋白表达明显增加(P0.01),皮层与海马组织中PP2A-Cα和PP2A-Cβ及海马组织中PP2CB蛋白表达明显降低(P0.05),皮层中PP2CA和PP2CB的蛋白表达明显增加(P0.01),皮层中PP1的蛋白表达明显降低(P0.01)。与模型大鼠比较,灌胃25、50和100 mg/kg SSF 36 d不同程度地逆转了OA所致大鼠皮层与海马组织中PHF、PP2A-Cα和PP2ACβ及皮层中PP1的蛋白表达异常,对PP2CA和PP2CB蛋白表达无显著性影响,银杏叶黄酮也表现出与SSF相似的结果。结论:SSF能够明显抑制OA引起的大鼠脑内PHF异常生成,该作用可能与SSF调节大脑皮层和海马组织中PP1、PP2A-Cα和PP2A-Cβ的蛋白表达有关,而与调节PP2CA和PP2CB的关系较小。     

Inhibitory effects of valproate on impairment of Y-maze alternation behavior induced by repeated electroconvulsive seizures and c-Fos protein levels in rat brains

We previously showed that inhibition of repeated electroconvulsive shock (ECS)-induced seizures through 7-day administration of anti-epileptic drugs suppressed the impairment of spontaneous alternation behavior in the Y-maze test in rats. To clarify the precise mechanism(s), we investigated the effect of valproate on such impairment and examined the levels of brain-derived neurotrophic factor (BDNF) and c-Fos protein in the prefrontal cortex and the hippocampus 24h after the last administration of ECS. Seven-day intraperitoneal (i.p.) administration of valproate (400mg/kg) suppressed the impairment of spontaneous alternation behavior. Repeated ECS increased the BDNF protein levels in the hippocampus and prefrontal cortex in the presence or absence of valproate, indicating that the increase in BDNF protein levels resulted from electrical stimulation. c-Fos protein levels were significantly decreased in the hippocampal dentate gyrus after repeated ECS, but valproate had no significant effect on decreased c-Fos protein levels. Valproate＋ECS significantly increased the c-Fos protein levels of the prefrontal cortex compared with the ECS group. These findings suggest that the inhibitory effect of valproate on repeated ECS-induced impairment of spontaneous alternation behavior may be linked to the prefrontal cortex.     

依达拉奉对血管性痴呆大鼠海马突触可塑性的影响

目的：探讨依达拉奉(edaravone,Eda)对血管性痴呆(vascular dementia,VD)大鼠海马CA1区神经元突触可塑性的调节作用及分子机制。方法：成年雄性SD大鼠30只,随机分成3组：假手术组、VD组、VD+Eda组,每组10只。应用Morris水迷宫(Morris water maze,MWM)测试各组大鼠的空间认知功能。MWM后,分别记录每只大鼠海马CA1区神经元长时程增强(long-term potentiation, LTP)并进行分析比较;电生理记录后,大鼠断头取脑,制备脑冰冻切片,免疫组织化学测定海马CA1区神经生长相关蛋白-43(GAP-43)的表达情况。结果：VD组大鼠有明显的空间认知障碍;Eda治疗后,VD+Eda组大鼠的空间认知障碍得到显著改善。VD+Eda组兴奋性突触后电位(excitatory postsynaptic potential,EPSP)斜率增加百分比显著高于VD组(P<0.05)。VD组GAP-43的表达量显著低于假手术组(P<0.01),VD+Eda组GAP-43的表达量显著高于VD组(P<0.05)。结论：依达拉奉可通过提高VD大鼠海马CA1区的突触可塑性改善空间认知障碍,其机制与依达拉奉上调VD大鼠海马CA1区GAP-43的表达有关。     

Analysis of sensitivity to MK-801 treatment in a novel active allothetic place avoidance task and in the working memory version of the Morris water maze reveals differences between Long-Evans and Wistar rats

The aims of the present study were to compare the effect of subchronic administration of MK-801 on performance in the active allothetic place avoidance (AAPA) task and in the working version of Morris water maze (MWM) in Long-Evans and Wistar rats. Animals were trained for four daily sessions either in the AAPA or in the working memory version of the MWM. Wistar rats treated by MK-801 (0.1 mg/kg) showed a cognitive deficit in the AAPA task without a significant hyperlocomotion, whereas they were not impaired in the working memory version of the MWM compared to controls. Long-Evans rats treated by MK-801 (0.1 mg/kg) were not impaired either in the AAPA task or in the MWM task. Higher doses of MK-801 (0.2 and 0.3 mg/kg) produced hyperlocomotion in both strains which corresponded to an inability to solve both spatial tasks. Long-Evans rats were superior in the MWM to the Wistar rats in the groups treated with the low dose of MK-801. In conclusion, intact Wistar rats can efficiently solve both spatial tasks; however, they are more sensitive to MK-801-induced behavioural deficit. This has relevance for modeling of the schizophrenia-related deficits and for screening substances for their therapeutic potential.     

Effects of chronic noise stress on spatial memory of rats in relation to neuronal dendritic alteration and free radical-imbalance in hippocampus and medial prefrontal cortex

Spatial memory is coordinated with different brain regions especially hippocampus (HIP) and medial prefrontal cortex (mPFC). Influence of noise stress on working and reference memory error in rats was evaluated by radial eight-arm maze experiment. Changes in the dendritic count were observed in the brain regions such as CA1, CA3 regions of HIP and layers II, III of mPFC. In order to understand the possible mechanism behind noise stress-induced changes, free radical status and acetylcholinesterase (AChE) activity in HIP and mPFC were evaluated. Plasma corticosterone level was also evaluated. Results obtained in this study showed that after noise-stress exposure, 100 dBA/4h per day for 30 days, working and reference memory error increased significantly (P < 0.05) when compared to control animals. Neuronal dendritic count in the HIP was reduced in the 2nd and 3rd order dendrites but not in the mPFC. Superoxide dismutase, lipid peroxidation, plasma corticosterone level and AChE activity were significantly increased in the 1 day, 15 days and 30 days stress groups animal significantly. Catalase and glutathione peroxidase activity were increased in the 1 day and 15 days noise-stress groups but decreased in the 30 days noise-stress group and GSH level was decreased in all the stress exposed animals. In conclusion, oxidative stress, increased AChE activity, reduced dendritic count in HIP, mPFC regions and elevated plasma corticosterone level which develops in long-term noise-stress exposed rats, might have caused the impairment of spatial memory.     

Muscarinic receptor-mediated GTP-Eu binding in the hippocampus and prefrontal cortex is correlated with spatial memory impairment in aged rats

The present study examined muscarinic receptor/G-protein coupling in the hippocampus and the prefrontal cortex of young and aged Long-Evans rats characterized for spatial learning ability in the Morris water maze. In a highly sensitive time-resolved fluorometry GTP-Eu binding assay, muscarinic-mediated GTP-Eu binding was severely blunted in hippocampus (-32%) and prefrontal cortex (-34%) as a consequence of aging. Furthermore, the magnitude of decreased muscarinic-mediated GTP-Eu binding was significantly correlated with the severity of spatial learning impairment in hippocampus and prefrontal cortex of aged rats and was specifically decreased in the subset of aged rats that were spatial learning impaired when compared to the aged unimpaired and the young rats. Western blot data indicated a preservation of the membrane-bound M1 receptor and the Galphaq/11 protein in both brain regions. These data demonstrate that muscarinic signaling is severely impaired as a consequence of normal aging in a manner that is closely associated with age-related cognitive decline.