Transgenic expression of the protein-L-isoaspartyl methyltransferase (PIMT) gene in the brain rescues mice from the fatal epilepsy of PIMT deficiency

Protein-L-isoaspartyl methyltransfearase (PIMT) plays a physiological role in the repair of damaged proteins containing isoaspartyl residues. In previous studies, we showed that PIMT-deficient mice developed a fatal epileptic seizure associated with the accumulation of damaged proteins in the brain. The mutant mice also showed a neurodegenerative pathology in hippocampi and impaired spatial memory. Still undefined, however, is how the accumulation of isoaspartates leads to the death of PIMT-deficient mice. In the present study, we generated PIMT transgenic (Tg) mice to investigate whether the exogenous expression of PIMT could improve the symptoms associated with PIMT deficiency. Rescue experiments showed that Tg expression of PIMT driven by a prion promoter effectively cured the PIMT-deficient mice. Biochemically, a higher expression level of transgene led to the effective repair of damaged proteins in vivo. Although a lower level of expression caused an accumulation of damaged proteins in a partially rescued line, the mice survived. Interestingly, synapsin I, which was extensively modified posttranslationally in PIMT-deficient mice, was specifically repaired in a partially rescued, but symptom-improved, Tg line. Our results suggest that an overall accumulation of damaged proteins does not necessarily lead to a fatal epileptic seizure, whereas certain modifications, such as changes in synapsin I, may play a pivotal pathological role in epilepsy.     

Facilitated CA1 hippocampal synaptic plasticity in dystrophin‐deficient mice: Role for GABAA receptors?

Duchenne muscular dystrophy (DMD) is associated with cognitive deficits that may result from a deficiency in the brain isoform of the cytoskeletal membrane-associated protein, dystrophin. CA1 hippocampal short-term potentiation (STP) of synaptic transmission is increased in dystrophin-deficient mdx mice, which has been attributed to a facilitated activation of NMDA receptors. In this study, extracellular recordings in the hippocampal slice preparation were used first to determine the consequences of this alteration on short-term depression (STD). STD induction was facilitated in mdx as compared with wild-type mice in a control medium. Because brain dystrophin deficiency results in a decreased number of gamma-aminobutyric acid A (GABAA)-receptor clusters, we tested the hypothesis that neuronal disinhibition contributes to the enhanced synaptic plasticity in mdx mice. We found that the GABAA receptor antagonist, bicuculline, increased basal neurotransmission in wild-type, but not in mdx mice and prevented the enhanced STP and STD in the CA1 area of slices from mdx mice. The possibility that altered GABA mechanisms underlie the facilitation of NMDA receptor-dependent synaptic plasticity in mdx mice is discussed.     

In vitro H-serotonin (5-HT) synthesis and release in BALBc and C57BL mice. II. Cell body areas

"In vitro" 3H-5-HT and 3H-5-HIAA, newly synthesized from 3H-TRP, are measured in the brainstem, the anterior raphe nuclei and the locus coeruleus of C57BL and BALBc mice. As found for the caudate nucleus and the hippocampus, higher synthesis and release are determined in C57BL than in BALBc, for the locus coeruleus and more globally, for the brainstem. But these differences disappear when the study is carried on the raphe dorsalis and the raphe centralis nuclei. Therefore the serotonergic activity could be independently regulated at the level of cell bodies and at those of terminals. However, the 5-HT metabolism of NRD of BALBc mice could be submitted to a specific autoinhibition which could explain a lower 5-HT synthesis and release at the corresponding terminal level, compared to C57BL.     

胎盘多肽对肿瘤细胞生长抑制作用研究

目的　探讨胎盘多肽 (PPs)对小鼠肿瘤细胞体内、外生长的影响。方法　染料排斥试验及肿瘤细胞体内种植实验。结果　PPs在体外对肿瘤细胞无明显的直接杀伤作用 (P >0 0 5 ) ,但体内肿瘤种植实验中给药组H2 2 腹水瘤小鼠生命延长率为 70 % ,S180 实体瘤生长抑制率为 6 5 % ,与对照组相比实验组荷瘤小鼠生存时间有显著差异 (P <0 0 1 )且肿瘤的形成也有明显的抑制作用 (P <0 0 1 )。结论　PPs在体内有明显的抑瘤作用     

Genetic mapping of ASIC4 and contrasting phenotype to ASIC1a in modulating innate fear and anxiety

Although ASIC4 is a member of the acid‐sensing ion channel (ASIC) family, we have limited knowledge of its expression and physiological function in vivo. To trace the expression of this ion channel, we generated the ASIC4‐knockout/CreERT²‐knockin (Asic4^CreERT2) mouse line. After tamoxifen induction in the Asic4^CreERT2::CAG‐STOP^floxed‐Td‐tomato double transgenic mice, we mapped the expression of ASIC4 at the cellular level in the central nervous system (CNS). ASIC4 was expressed in many brain regions, including the olfactory bulb, cerebral cortex, striatum, hippocampus, amygdala, thalamus, hypothalamus, brain stem, cerebellum, spinal cord and pituitary gland. Colocalisation studies further revealed that ASIC4 was expressed mainly in three types of cells in the CNS: (i) calretinin (CR)‐positive and/or vasoactive intestine peptide (VIP)‐positive interneurons; (ii) neural/glial antigen 2 (NG2)‐positive glia, also known as oligodendrocyte precursor cells; and (iii) cerebellar granule cells. To probe the possible role of ASIC4, we hypothesised that ASIC4 could modulate the membrane expression of ASIC1a and thus ASIC1a signaling in vivo. We conducted behavioral phenotyping of Asic4^CreERT2 mice by screening many of the known behavioral phenotypes found in Asic1a knockouts and found ASIC4 not involved in shock‐evoked fear learning and memory, seizure termination or psychostimulant‐induced locomotion/rewarding effects. In contrast, ASIC4 might play an important role in modulating the innate fear response to predator odor and anxious state because ASIC4‐mutant mice showed increased freezing response to 2,4,5‐trimethylthiazoline and elevated anxiety‐like behavior in both the open‐field and elevated‐plus maze. ASIC4 may modulate fear and anxiety by counteracting ASIC1a activity in the brain.     

经鼻滴入海人藻酸引起C57BL/6小鼠嗅球和海马区神经元的退行性病变

目的 应用海人藻酸(KA)在C57BL／6小鼠建立神经退行性病变动物模型并观察其对嗅球神经元的影响。方法 经鼻滴人KA应用尼氏和嗜银染色观察海马及嗅球的病理变化，免疫组化检测Cyclooxygenase2(COX-2)的表达。结果 经鼻滴入KA成功地在C57BL／6小鼠建立了神经退行性病变动物模型，KA通过嗅神经引起双侧嗅球和海马损伤，其病变程度与小鼠体重和滴入KA剂量有关，同时KA引起了脑内明显的胶质细胞增生和炎症因子COX-2在嗅球部的表达。结论 经鼻滴入KA能够引起嗅球和海马的损伤。     

Systemic overexpression of the alpha 1B-adrenergic receptor in mice: an animal model of epilepsy

PURPOSE: A lack of selective alpha1-adrenergic receptor (alpha1-ARs) agonists and antagonists has made it difficult to clarify the precise function of these receptors in the CNS. We recently generated transgenic mice that overexpress either wild-type or a constitutively active mutant alpha 1B-AR in tissues that normally express the receptor. Both wild-type and mutant mice showed an age-progressive neurodegeneration with locomotor impairment and probable stress-induced motor events, which can be partially reversed by alpha 1-AR antagonists. We hypothesized that the wild-type and mutant mice may exhibit spontaneous epileptogenicity as compared with normal (nontransgenic) mice. METHODS: Normal, wild-type, and mutant mice were studied. Twenty mice (1 year old) underwent prolonged video-EEG monitoring over a 4-week period. Raw EEG data were blindly analyzed by visual inspection for the presence of interictal and ictal epileptic activities. RESULTS: During the acute postoperative period (< or = 3 days), both wild-type (26.1 +/- 8.07 spikes/day) and mutant mice (116.87 +/- 55.13) exhibited more frequent interictal spikes than did normal mice (2.17 +/- 0.75; p value, <0.05), but all three groups showed EEG and clinical seizures. During the later monitoring periods (>3 days), wild-type and mutant mice showed more frequent interictal spikes (15.44 +/- 4.07; p < 0.01; and 6.05 +/- 2.46; p < 0.05, respectively) as compared with normal mice (0.41 +/- 0.41), but only mutant mice had spontaneous clinical seizures (means +/- SEM). CONCLUSIONS: The selective overexpression of the alpha 1B-AR is associated with increased in vivo spontaneous interictal epileptogenicity and EEG/behavioral seizures. These results suggest a possible role (direct or indirect) for the alpha 1B-ARs in the development and expression of epileptogenicity.     

Dysregulation of dopamine signaling in the dorsal striatum inhibits feeding

Dopamine signaling is an important component of many goal-directed behaviors, such as feeding. Acute disruption of dopamine signaling using pharmacological agents tends to inhibit normal feeding behaviors in rodents. Likewise, genetically engineered dopamine-deficient (DD) mice are unable to initiate sufficient feeding and will starve by approximately 3 weeks of age if untreated. Adequate feeding by DD mice can be achieved by daily administration of L-3,4-dihydroxyphenylalanine (L-dopa), a precursor of dopamine, which can be taken up by dopaminergic neurons, converted to dopamine, and released in a regulated manner. In contrast, adequate feeding cannot be restored with apomorphine (APO), a mixed agonist that activates D1 and D2 receptors. Viral restoration of dopamine production in neurons that project to the dorsal striatum also restores feeding in DD mice. Administration of amphetamine (AMPH) or nomifensine (NOM), drugs which increase synaptic dopamine concentration, inhibits food intake in virally rescued DD mice (vrDD) as in control animals. These results indicate that the dysregulation of dopamine signaling in the dorsal striatum is sufficient to induce hypophagia and suggest that regulated release of dopamine in that brain region is essential for normal feeding and, probably, many other goal-directed behaviors.     

Redefining the Koizumi model of mouse cerebral ischemia: A comparative longitudinal study of cerebral and retinal ischemia in the Koizumi and Longa middle cerebral artery occlusion models

Cerebral and retinal ischemia share similar pathogenesis and epidemiology, each carrying both acute and prolonged risk of the other and often co-occurring. The most used preclinical stroke models, the Koizumi and Longa middle cerebral artery occlusion (MCAO) methods, have reported retinal damage with great variability, leaving the disruption of retinal blood supply via MCAO poorly investigated, even providing conflicting assumptions on the origin of the ophthalmic artery in rodents. The aim of our study was to use longitudinal in vivo magnetic resonance assessment of cerebral and retinal vascular perfusion after the ischemic injury to clarify whether and how the Koizumi and Longa methods induce retinal ischemia and how they differ in terms of cerebral and retinal lesion evolution. We provided anatomical evidence of the origin of the ophthalmic artery in mice from the pterygopalatine artery. Following the Koizumi surgery, retinal responses to ischemia overlapped with those in the brain, resulting in permanent damage. In contrast, the Longa method produced only extensive cerebral lesions, with greater tissue loss than in the Koizumi method. Additionally, our data suggests the Koizumi method should be redefined as a model of ischemia with chronic hypoperfusion rather than of ischemia and reperfusion.     

High frequency stimulation of the subthalamic nucleus impacts adult neurogenesis in a rat model of Parkinson's disease

APP.V717I and Tau.P301L transgenic mice develop Alzheimer's disease pathology comprising important aspects of human disease including increased levels of amyloid peptides, cognitive and motor impairment, amyloid plaques and neurofibrillary tangles. The combined model, APP.V717I × Tau.P301L bigenic mice (biAT mice) exhibit aggravated amyloid and tau pathology with severe cognitive and behavioral defects. In the present study, we investigated early changes in synaptic function in the CA1 and CA3 regions of acute hippocampal slices of young APP.V717I, Tau.P301L and biAT transgenic animals. We have used planar multi-electrode arrays (MEA) and improved methods for simultaneous multi-site recordings from two hippocampal sub-regions. In the CA1 region, long-term potentiation (LTP) was severely impaired in all transgenic animals when compared with age-matched wild-type controls, while basal synaptic transmission and paired-pulse facilitation were minimally affected. In the CA3 region, LTP was normal in Tau.P301L and APP.V717I but clearly impaired in biAT mice. Surprisingly, frequency facilitation in CA3 was significantly enhanced in Tau.P301L mice, while not affected in APP.V717I mice and depressed in biAT mice. The findings demonstrate important synaptic changes that differ considerably in the hippocampal sub-regions already at young age, well before the typical amyloid or tau pathology is evident.