An optimal dose of tea polyphenols protects against global cerebral ischemia/reperfusion injury

Previous studies addressing the protection of tea polyphenols against cerebral ischemia/ reperfusion injury often use focal cerebral ischemia models, and the optimal dose is not unified. In this experiment, a cerebral ischemia/reperfusion injury rat model was established using a modified four-vessel occlusion method. Rats were treated with different doses of tea polyphenols (25, 50, 100, 150, 200 mg/kg) via intraperitoneal injection. Results showed that after 2, 6, 12, 24, 48 and 72 hours of reperfusion, peroxide dismutase activity and total antioxidant capacity in brain tissue gradually increased, while malondialdehyde content gradually decreased after tea polyphenol intervention. Tea polyphenols at 200 mg/kg resulted in the most apparent changes. Terminal deoxynucleotidyl transferase-mediated nick end labeling and flow cytometry showed that 200 mg/kg tea polyphenols significantly reduced the number and percentage of apoptotic cells in the hippocampal CA1 region of rats after cerebral ischemia/reperfusion injury. The open field test and elevated plus maze experiments showed that tea polyphenols at 200 mg/kg strengthened exploratory behavior and reduced anxiety of cerebral ischemia/reperfusion injured rats. Experimental findings indicate that tea polyphenols protected rats against cerebral ischemia/ reperfusion injury and 200 mg/kg is regarded as the optimal dose.     

Spatial Resolution of an Eye Containing a Grouped Retina: Ganglion Cell Morphology and Tectal Physiology in the Weakly Electric Fish Gnathonemus petersii

The retina of the weakly electric fish Gnathonemus petersii is a so‐called grouped retina where photoreceptors are bundled. These bundles are regarded as functional units and this type of retinal specialization is uniquely found in teleosts. To understand how this anatomical organization influences visual information processing we investigated the morphology and distribution of retinal ganglion cells (GCs) and the response properties of retinal afferents terminating in the major retinorecipient area, the optic tectum. GCs were classified based on their dendritic morphology (dendritic field diameters <90–100 μm: narrow‐field GCs; 110–280 μm: widefield GCs; >280 μm: giant GCs). Within these classes subtypes were distinguished based on the ramification patterns of the dendrites in the sublaminae of the inner plexiform layer. Properties of presumed optic nerve terminals were investigated in the optic tectum using extracellular recordings. Physiological classes could be observed based on their response to visual stimuli (on; off; on‐off, and fast units). Receptive field sizes and spatiotemporal properties were classified and the topographical representation of the visual space was mapped in the tectum. Gratings of low spatial frequencies were best responded to and followed up to high temporal frequencies (>30 Hz). Most of the recorded units were directionally selective. No evidence of distorted topographies in the tectum was found, i.e., no overrepresentation of the retina was seen in the tectum opticum. The grouped retina of G. petersii seems to be optimized for the detection of large, fast objects in an environment of low optical quality. J. Comp. Neurol. 521:4075–4093, 2013. © 2013 Wiley Periodicals, Inc.     

胚胎期暴露DEHP对子代大鼠神经行为的影响

目的通过邻苯二甲酸二(2-乙基己基)酯(DEHP)胚胎期暴露,评价其对子代大鼠神经行为的影响,初步探讨DEHP所致子鼠神经毒性的机制。方法雌性Wistar大鼠从妊娠日起用10、100、500 mg/(kg.d)DEHP连续灌胃染毒19 d,观察子代大鼠的神经行为学指标。于子鼠出生第7天和第21天测定海马神经细胞凋亡率,不同剂量的DEHP染毒对海马组织bcl-2、bax基因的表达的影响。结果于子鼠出生6周后,进行水迷宫测试。结果显示,随着DEHP剂量增加,中、高剂量组错误次数增加和潜伏期延长十分明显(F=8.058,P<0.05;F=11.221,P<0.05)。电穿梭测试显示,中、高剂量组电击次数增加和主动逃避时间延长较为明显(F=6.984,P<0.05;F=9.841,P<0.05)。出生后7 d子代大鼠海马神经元的细胞凋亡率高于出生21 d,高剂量组尤为显著。RT-PCR检测表明,与对照组相比,bcl-2和bax基因表达增高(F=253.78,P<0.05;F=66.67,P<0.05),且随着DEHP暴露剂量的升高,表达亦增加。结论 DEHP对子代大鼠神经系统具有明显的毒性作用,存在着剂量-反应关系,其可能通过干扰bcl-2和bax基因的表达而影响子代大鼠神经系统发育。     

Effects of tegmental lesions on the isolation call of squirrel monkeys

The present study is concerned with identifying brain mechanisms underlying a basic mammalian vocalization known as the isolation call. The call serves to reestablish contact of separated individuals. Adult squirrel monkeys were used as experimental subjects because the isolation call in these animals has been shown to be stable, well-defined, and readily elicited under experimental conditions. Bilateral, symmetrical electrocoagulations in certain parts of the tegmentum and core gray matter of the thalamus and midbrain variously altered the character and production of isolation calls, but had no apparent effect on other vocalizations. In respective cases the changes were characterized by: (1) reduction in number of calls; (2) calls with abnormal structure; and (3) calls of infantile character. As opposed to earlier investigations on mammals, the present study has shown that damage to certain brain structures may not only affect the production of a vocalization but also its physical characteristics.     

Toward a neuroethology of mammalian vision: Ecology and anatomy of rodent visuomotor behavior

The great diversity of the niches inhabited by rodents, and the variety of the visual demands of these niches, present an excellent prospect for a comprehensive neuroethological analysis of rodent visuomotor behavior. To this end, rodent taxonomy is reviewed, with special attention to the multiple independent invasions of arboreal, terrestrial, fossorial and aquatic niches by distantly related rodent species. Current work on rat, gerbil and hamster is reviewed with emphasis on visual contributions to naturalistic behaviors such as exploration, foraging, predator detection and conspecific recognition.     

Serotonin selectively enhances perception and sensory neural responses to stimuli generated by same-sex conspecifics

Centrifugal serotonergic fibers innervating sensory brain areas are seen ubiquitously across systems and species but their function remains unclear. Here we examined the functional role of serotonergic innervation onto electrosensory neurons in weakly electric fish by eliciting endogenous release through electrical stimulation as well as exogenous focal application of serotonin in the vicinity of the cell being recorded from. Both approaches showed that the function of serotonergic input onto electrosensory pyramidal neurons is to render them more excitable by reducing the spike afterhyperpolarization amplitude and thereby promoting burst firing. Further, serotonergic input selectively improved neuronal responses to stimuli that occur during interactions between same-sex conspecifics but not to stimuli associated with either prey or that occur during interactions between opposite-sex conspecifics. Finally, we tested whether serotonin-mediated enhanced pyramidal neuron responses to stimuli associated with same-sex conspecifics actually increase perception by the animal. Our behavioral experiments show that exogenous injection and endogenous release of serotonin both increase the magnitude of behavioral responses to stimuli associated with same-sex conspecifics as well as simultaneously decrease aggressive behaviors. Thus, our data indicate that the serotonergic system inhibits aggressive behavior toward same-sex conspecifics, while at the same time increasing perception of stimuli associated with these individuals. This function is likely to be conserved across systems and species.Animals must efficiently process natural sensory stimuli to successfully interact with their environment. It has become clear in recent years that sensory processing is not a passive process but instead actively depends on behavioral context (1). Adaptive control of sensory processing is in part achieved through neuromodulators such as serotonin (2). However, the functional role of serotonergic fibers emanating from the raphe nuclei innervating sensory brain areas remains largely unclear (3). This is in part because these fibers make diverse patterns of connectivity (4, 5), thereby causing a wide range of effects, such as response attenuation and gating (6, 7), as well as response enhancement (7). Thus, it is generally agreed that the function of serotonergic input onto sensory neurons is to enhance their responses to given stimulus features while attenuating responses to other features. As such, studies performed in model organisms well characterized anatomically, behaviorally, and physiologically are likely to speed progress toward a general understanding of how serotonin alters neuronal responses to natural stimuli as well as consequences on perception and behavior.The weakly electric fish Apteronotus leptorhynchus generates a quasisinusoidal electric field through the electric organ discharge (EOD) (8). Electroreceptive neurons scattered on the skin surface monitor perturbations of this field caused by objects with conductivity different from that of the surrounding water and relay this information to pyramidal neurons within the electrosensory lateral line lobe (ELL). In particular, there are two important categories of behaviorally relevant electrosensory stimuli: those caused by prey are typically localized within a small region of the animal’s skin (9), whereas stimuli caused by conspecifics are typically diffuse and impinge on most if not all of the skin surface (8). In particular, when two fish come into contact (i.e., are within 1 m of one another), each animal will experience an amplitude modulation of its own EOD that oscillates at the difference between the two EOD frequencies (i.e., a beat). Because of a sexual dimorphism in EOD frequency, interactions between same-sex conspecifics tend to give rise to low frequency beats (<30 Hz), whereas interactions between opposite-sex conspecifics tend to give rise to higher frequency (30–400 Hz) beats (10). Moreover, these fish emit communication calls termed “chirps” during both agonistic and courtship behaviors that consist of brief modulations of their EOD. In particular, small chirps are preferentially elicited during encounters between same-sex conspecifics, whereas big chirps are preferentially elicited during encounters between opposite-sex conspecifics (10). The responses of ELL pyramidal neurons to such stimuli have been well characterized (8). Recent studies performed in vitro have shown that serotonin renders ELL pyramidal neurons more excitable by down-regulating potassium channels that contribute to the spike afterhyperpolarization (AHP) (11, 12). However, the effects of serotonin on the processing of behaviorally relevant stimuli by pyramidal neurons in vivo and its consequences on behavior have not been investigated to date.Here, we used a systems level approach with behaviorally relevant stimuli to understand the functional role of serotonergic input onto ELL pyramidal neurons. We found that exogenous application of serotonin and endogenous release via electrical stimulation of serotonergic pathways both led to increased excitability and burst firing. Also, serotonin release enhanced pyramidal neuron responses to the low-frequency stimuli that occur during interactions between same-sex conspecifics as well as agonistic communication calls, but not to stimuli mimicking prey, opposite-sex conspecifics, or courtship communication calls. Finally, we found that both endogenous release and injection of serotonin caused enhanced behavioral responses to stimuli mimicking same-sex conspecific interactions, while simultaneously reducing aggressive behavior. We conclude that the functional role of serotonin is to enhance perception of stimuli associated with aggressive individuals, while at the same time promoting their avoidance through covert behavior. Our results thus demonstrate an important function for serotonergic input onto sensory neurons and its consequences at the organismal level.     

All in the Family – Touch Versus Olfaction in Moles

Here I review, compare, and contrast the neurobiology and behavior of the common, eastern mole (Scalopus aquaticus) and the star-nosed mole (Condylura cristata). These two species are part of the same family (Talpidae) and have similar body size and general morphology. But they differ in sensory specializations, complexity of neocortical organization, and behavior. The star-nosed mole has an elaborate mechanosensory organ—the star—consisting of 22 epidermal appendages (rays) covered with 25,000 touch domes called Eimer's organs. This densely innervated structure is represented in the neocortex in three different somatosensory maps, each visible in flattened neocortical sections as a series of 11 modules representing the 11 rays from the contralateral body. The 11th ray is greatly magnified in primary somatosensory cortex (S1). Behavioral studies show the star is moved in a saccadic manner and the 11th ray is a high-resolution tactile fovea, allowing star-nosed moles to forage on small prey with unprecedented speed and efficiency. In contrast, common mole noses lack Eimer's organs, their neocortex contains only two cortical maps of the nose, and they cannot localize small prey. Yet common moles have exceptional olfactory abilities, sniffing in stereo to rapidly localize discrete odor sources originating from larger prey. In addition, common moles are shown to track odorant trails laid down by moving prey. These results highlight the surprising abilities of species once thought to be simple, and the usefulness of diverse species in revealing general principles of brain organization and behavior. Anat Rec, 2019. © 2019 American Association for Anatomy.     

Mechanosensory appendages and giant interneurons in the firebrat (Thermobia domestica, Thysanura): a prototype system for terrestrial predator evasion

Aspects of the structure and function of the abdominal cerci and caudal filament sensory systems, and associated giant interneurons of the thysanuran insect Thermobia domestica, the firebrat, extend comparative studies of a widespread predator evasion system. All elements of the cercal system, which is well known from diverse orthopteroid insects, are present in the primitively wingless thysanuran. In addition, a median terminal sensory appendage, the caudal filament, projects to the same general regions of the terminal ganglion but shows limited overlap of synaptic regions with cercal input. A segmental series of giant interneurons appears to be homologous with those of the orthopteroid insects. The cercal system, which may have evolved with the first terrestrial hexapods, reaches its zenith in the orthopteroid insects, but was replaced in holometabolan insects by visual startle mechanisms with descending giant interneurons.     

芍甘木瓜汤通过BDNF/TrkB/CREB信号通路改善脑卒中偏瘫痉挛状态大鼠神经行为学研究

目的 观察芍甘木瓜汤对脑卒中偏瘫痉挛状态大鼠神经行为学的影响,并探讨对脑源性神经营养因子（BDNF）/酪氨酸蛋白激酶B（TrkB）/环磷腺苷效应元件结合蛋白（CREB）信号通路的调控机制。方法 取50只SD大鼠采用改良线栓法制作大脑中动脉梗死模型,选取建模成功大鼠随机分为模型组、巴氯芬（0.008 g/kg）组和芍甘木瓜汤低、中、高剂量（0.05、0.10、0.15 g/kg）组。另取10只SD大鼠不栓塞大脑中动脉作为假手术组,于再灌注2 h后ig给药,每天1次,连续2周,假手术组和模型组ig等量生理盐水。干预前后分别采用Zea Longa量表、改良Ashworth量表评价神经行为学、肌张力变化,采用大鼠多导生理记录仪测定上肢伸直幅度;酶联免疫法检测大鼠干预前后血清BDNF、TrkB水平;苏木素-伊红（HE）染色观察缺血半暗带脑组织病理变化,透射电镜下观察缺血半暗带脑组织神经元超微结构;实时荧光定量PCR（qRT-PCR）检测缺血半暗带脑组织BDNF、TrkB-FL、TrkB-T1、CREB mRNA表达;Western blotting检测BDNF、TrkB-FL、TrkB-T1、CREB蛋白表达及p-CREB水平。结果 干预后巴氯芬组和芍甘木瓜汤各剂量组的Zea Longa量表、改良Ashworth量表分级均较干预前和模型组（干预后）显著改善（P<0.05）,上肢伸直幅度均较干预前和模型组（干预后）均显著增加（P<0.05）,血清BDNF、TrkB水平均较干预前和模型组（干预后）显著升高（P<0.05）,缺血半暗带脑组织病理变化和神经元超微结构均较模型组明显改善。模型组缺血半暗带脑组织BDNF、TrkB-FL mRNA与蛋白表达,p-CREB蛋白水平均显著低于假手术组（P<0.05）,巴氯芬组和芍甘木瓜汤各剂量组均较模型组显著升高（P<0.05）;模型组缺血半暗带脑组织TrkB-T1 mRNA与蛋白表达显著高于假手术组（P<0.05）,巴氯芬组和芍甘木瓜汤各剂量组均较模型组显著下降（P<0.05）。各组缺血半暗带脑组织CREB mRNA表达差异无统计学意义。结论 对脑卒中偏瘫痉挛状态大鼠ig予以芍甘木瓜汤可改善其神经行为学,降低肌张力,增加血清BDNF、TrkB水平,减轻缺血半暗带脑组织病理和神经元超微结构变化,推测与激活BDNF/TrkB/CREB通路,上调BDNF、TrkB-FL mRNA与蛋白表达,下调TrkB-T1 mRNA与蛋白表达,增加p-CREB水平有关。     

碱性成纤维细胞生长因子对颅脑损伤后神经行为学的影响

目的 研究碱性成纤维细胞生长因子（bFGF）对颅脑损伤后神经行为学的影响及其有关机制。方法 将30只SD大鼠随机分成正常组、假手术组、外伤对照组、bFGF治疗组和生理盐水对照组。建立大鼠侧方液压颅脑外伤模型,观察神经行为学,脑组织含水量,脑组织损伤面积及病理学变化。结果 与外伤对照组及生理盐水对照组相比,bFGF能促进神经功能的恢复,并降低脑组织的含水量,减少损伤面积（P＜0．05）,并能减轻颅脑损伤后的病理学损害。结论 bEGF有助于颅脑损伤后的神经行为学的恢复,其机制与减轻脑水肿,减少脑组织损伤有关。