Dopamine release regulation by astrocytes during cerebral ischemia

The effect of triple reuptake inhibitor toludesvenlafaxine on neurological function in cerebral ischemic rats

Purpose: The aim is to investigate the effect of toludesvenlafaxine (Tdv), a reuptake inhibitor of serotonin, norepinephrine, and dopamine, on the neurological function in cerebral ischemic rats and the underlying mechanisms. Material and Methods: Middle cerebral artery occlusion/reperfusion (MCAO/R) model was induced in rats and the neuroprotective effects of Tdv were evaluated by infarct size, Garcia test, and beam walking test. Neuronal apoptosis in the peri-infarct area was observed by TUNEL staining. And the apoptosis-related proteins were evaluated with Western blotting. The role of CREB pathway in effect of Tdv was also investigated using Western blotting and immunofluorescence. Results: In the MCAO/R model, administration of Tdv reduced the infarct size, promoted neural functional recovery, decreased the expression of Bax and Caspase-3, and increased the expression of Bcl-2 and BDNF. In addition, Tdv reduced neuronal apoptosis in the peri-infarct area. Tdv increased the expression of phosphorylated CREB. The application of the specific CREB inhibitor, compound 666-15, could reverse the anti-ischemic cerebral injury of Tdv in MCAO/R rats. Conclusion: Tdv ameliorated cerebral ischemic injury through reducing neuronal apoptosis and increasing the expression of BDNF via the activation of CREB pathway.

Exercise on Striatal Dopamine Level and Anxiety-Like Behavior in Male Rats after 2-VO Cerebral Ischemia

The purpose of this study was to discuss the effect of voluntary wheel running on striatal dopamine levels and anxiety-like behavior in rats with global cerebral ischemia. The male Sprague-Dawley rats were signed on in this study and randomly divided into following 4 groups: Control group (C group), Sham group (S group), ischemia group (I group), and 3 weeks physical exercise before ischemia group (3RI group). The rats in the 3RI group were placed in a voluntary running wheel for three weeks to exercise. Then, the rats in I and 3RI groups received bilateral carotid artery ligation (2-VO) operation. The C and S group did not perform voluntary running exercise and the bilateral common carotid arteries of S group were exposed without ligation. In vivo microdialysis was used in conjunction with high performance liquid chromatography (HPLC) and electrochemical detection to ascertain the level of dopamine in the striatum. Elevated plus maze (EPM) and open field (OF) were used to test anxiety status at 24 hours and 7days after 2-VO cerebral ischemia. Meanwhile, gait and motor coordination evaluations were carried out to eliminate the influence of non-specific motor problems. The results indicated that cerebral ischemia instigate the increase of striatal dopamine in I group rats during acute cerebral ischemia. A 3-week voluntary wheel running significantly enhances the striatal dopamine before ischemia and obstructs a further increase of dopamine during acute cerebral ischemia in 3RI group rats. At 24 hours after ischemia, striatal dopamine returned to pre-ischemic levels in 3RI group. Striatal dopamine in I group were less than pre-ischemic levels at 7 days. Behavioral data indicated that 3-week voluntary wheel running promoted recovery of anxiety-like behavior and gait were not affected by 2-VO cerebral ischemia at 24 hours post-ischemia rats. Therefore, it can be concluded that 3-week physical exercise significantly increased the striatal dopamine and improved anxiety-like behavior by inhibiting the increase of dopamine during acute cerebral ischemia and suppressing the decrease of dopamine after 24 hours and 7 days cerebral ischemia.

Hippocampal metabolic recovery as a manifestation of the protective effect of ischemic preconditioning in rats

The ever-present risk of brain ischemic events in humans and its full prevention make the detailed studies of an organism's response to ischemia at different levels essential to understanding the mechanism of the injury as well as protection. We used the four-vessel occlusion as an animal model of forebrain ischemia to investigate its impact on the metabolic alterations in both the hippocampus and the blood plasma to see changes on the systemic level. By inducing sublethal ischemic stimuli, we focused on the endogenous phenomena known as ischemic tolerance. NMR spectroscopy was used to analyze relative metabolite levels in tissue extracts from rats' hippocampus and blood plasma in three various ischemic/reperfusion times: 3 h, 24 h, and 72 h. Hippocampal tissues were characterized by postischemically decreased glutamate and GABA (4-aminobutyrate) tissue content balanced with increased glutamine level, with most pronounced changes at 3 h reperfusion time. Glutamate (as well as glutamine) levels recovered towards the control levels on the third day, as if the glutamate re-synthesis would be firstly preferred before GABA. These results are indicating the higher feasibility of re-establishing of glutamatergic transmission three days after an ischemic event, in contrast to GABA-ergic. Tissue levels of N-acetylaspartate (NAA), as well as choline, were decreased without the tendency to recover three days after the ischemic event. Metabolomic analysis of blood plasma revealed that ischemically preconditioned rats, contrary to the non-preconditioned animals, did not show hyperglycemic conditions. Ischemically induced semi-ketotic state, manifested in increased plasma ketone bodies 3-hydroxybutyrate and acetoacetate, seems to be programmed to support the brain tissue revitalization after the ischemic event. These and other metabolites changes found in blood plasma as well as in the hippocampus were observed to a lower extent or recovered faster in preconditioned animals. Some metabolomic changes in hippocampal tissue extract were so strong that even single metabolites were able to differentiate between ischemic, ischemically preconditioned, and control brain tissues.

Sustained delivery of focal ischemia coupled to real-time neurochemical sensing in brain slices

Local stimulation of tissue can occur naturally in events like immune-mediated inflammation and focal ischemic injuries in brain and is confined to specific regions within tissue, occurring on various timescales. Making chemical measurements at the exact site of stimulation with current technologies is difficult yet important for understanding tissue response. We have developed a microfluidic device capable of local stimulation of brain slices with minimal lateral spread over time and submillimeter, tunable spatial resolution. This device is compatible with electrochemical measurements to monitor signaling at the site of stimulation over time. The PDMS-based device is three layers and contains a culture well, channel layer, and exit port layer for the channels. Channels with exit ports straddling the stimulus channels and ports were specifically fabricated to focus the stimulus over time. We demonstrated that the device is compatible with fast-scan cyclic voltammetry (FSCV) recording of neurotransmitter release. Localized hypoxia in tissue was verified using Image-iT Green Hypoxia Reagent and coupling this device with FSCV enabled measurement of local dopamine changes at the site of focal ischemia for the first time. This work provides a significant advance in knowledge of local neurochemical fluctuations during sustained tissue injury. Overall, the unique capabilities of the device to deliver sustained localized stimulation combined with real-time sensing provide an innovative platform to answer significant biological questions about how tissues respond at the site of controlled, localized injury and chemical stimulation.

Alpha-synuclein and cortico-striatal plasticity in animal models of Parkinson disease

Alpha-synuclein (α-synuclein) is a small, acidic protein containing 140 amino acids, highly expressed in the brain and primarily localized in the presynaptic terminals. It is found in high concentrations in Lewy Bodies, proteinaceous aggregates that constitute a typical histopathologic hallmark of Parkinson's disease. Altered environmental conditions, genetic mutations and post-translational changes can trigger abnormal aggregation processes with the increased frequency of oligomers, protofibrils, and fibrils formation that perturbs the neuronal homeostasis leading to cell death. Relevant to neuronal activity, a function of α-synuclein that has been extensively detailed is its regulatory actions in the trafficking of synaptic vesicles, including the processes of exocytosis, endocytosis and neurotransmitter release. Most recently, increasing attention has been paid to the possible role that α-synuclein plays at a postsynaptic level by interacting with selective subunits of the glutamate N-methyl-d-aspartate receptor, altering the corticostriatal plasticity of distinct neuronal populations.

Neuro-Immune Cross-Talk in the Striatum: From Basal Ganglia Physiology to Circuit Dysfunction

The basal ganglia network is represented by an interconnected group of subcortical nuclei traditionally thought to play a crucial role in motor learning and movement execution. During the last decades, knowledge about basal ganglia physiology significantly evolved and this network is now considered as a key regulator of important cognitive and emotional processes. Accordingly, the disruption of basal ganglia network dynamics represents a crucial pathogenic factor in many neurological and psychiatric disorders. The striatum is the input station of the circuit. Thanks to the synaptic properties of striatal medium spiny neurons (MSNs) and their ability to express synaptic plasticity, the striatum exerts a fundamental integrative and filtering role in the basal ganglia network, influencing the functional output of the whole circuit. Although it is currently established that the immune system is able to regulate neuronal transmission and plasticity in specific cortical areas, the role played by immune molecules and immune/glial cells in the modulation of intra-striatal connections and basal ganglia activity still needs to be clarified. In this manuscript, we review the available evidence of immune-based regulation of synaptic activity in the striatum, also discussing how an abnormal immune activation in this region could be involved in the pathogenesis of inflammatory and degenerative central nervous system (CNS) diseases.

Role of astrocytic GABAergic system on inflammatory cytokine-induced anxiety-like behavior

Recent studies have shown that not only neurons but astrocytes contain a considerable amount of γ-aminobutyric acid (GABA), which can be released and activate the receptors responsive to GABA. The purpose of this study is to test whether gliotransmitters from astrocytes may play a role in etiology of anxiety symptoms. Intracerebroventricular (i.c.v.) infusion of interleukin-1β (IL-1β), one of potent inflammatory cytokines, induced anxiety-like behaviors and activated the glial fibrillary acidic protein (GFAP) in the paraventricular nucleus (PVN) of the hypothalamus. Pretreatment with astrocytes toxin, l-α-aminoadipate (L-AAA) reduced anxiety-like behaviors and the GFAP expression in the PVN. Intraparaventricular nucleus (iPVN) infusion of IL-1β produced markedly anxiety-like behaviors and increased release of GABA from astrocytes. However, treatment of glial cell inhibitor, L-AAA or blocker of Bestrophin-1 (Best1), 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) markedly inactivated astrocytes and also reduced the anxiety-like behaviors. Treatment of L-AAA or NPPB decreased IL-1β-induced gliotransmitter GABA release measured by in vivo microdialysis. These results suggest that selective inhibition of astrocytes or astocytic GABA release in the PVN may serve as an effective therapeutic strategy for treating anxiety and affective disorders.

Temporal changes in physiological and molecular markers in various brain regions following transient global ischemia in rats

Several mechanisms are involved in the loss of cellular integrity and tissue destructions in various brain regions during ischemic insult. The affected brain employs various self-repair mechanisms during the poststroke recovery. Therefore, the current study involves time course changes in different brain regions following ischemia in terms of inflammation, oxidative stress and apoptosis for which a bilateral common carotid arteries occlusion model was chosen. The development of oxidative stress was seen with a marked increase in ROS and NO levels with concomitant decrease in GSH levels and also the activities of anti-oxidant enzymes. These alterations were accompanied with decreased levels of neurotransmitters and motor and cognitive deficits at various time points. Increased expressions of various pro-inflammatory cytokines and a decline in BDNF levels in hippocampal regions on 7th day post ischemia, suggesting their role in its pathogenesis. The restoration of BDNF and neurotransmitter levels along with significant decline in inflammatory cytokine levels 14th day onwards following ischemia in hippocampus suggested poststroke recovery. The extent of neuronal damage was found to be increased significantly on 7th day post ischemia as indicated by TUNEL assay and hematoxylin and eosin staining depicting enhanced number of pyknotic neurons in cortical and hippocampal regions. Cortical regions of the ischemic brains were severely affected while hippocampal regions showed significant poststroke recovery, which might attributed to the normalization of BDNF and pro-inflammatory cytokine levels. In conclusion, the present study established the central role of BDNF and pro-inflammatory cytokines in the poststroke recovery. Also, the cortical and hippocampal regions were found to be more susceptible for ischemic injury. As our results indicated, full recovery after ischemic injury in different brain regions was not achieved, therefore further studies with long-term recovery time are required to be conducted.

A Metabonomics Investigation into the Therapeutic Effects of BuChang NaoXinTong Capsules on Reversing the Amino Acid-Protein Interaction Network of Cerebral Ischemia

Background

Amino acids (AAs) in cerebrospinal fluid (CSF) play a pivotal role in cerebral ischemia (CI). BuChang NaoXinTong Capsules (BNC) are widely prescribed in Chinese medicine for the treatment of cerebrovascular and cardiovascular diseases.

Methods

In order to investigate the therapeutic effects and pharmacological mechanisms of BNC on reversing CI from a system level, an amino acid-protein interaction imbalanced network of CI containing metabolites of AAs, key regulatory enzymes, and proteins was constructed for the first time. Furthermore, a novel method for detecting the ten AAs in CSF was developed by UPLC-QQQ-MS in an effort to validate the imbalanced networks and the therapeutic effects of BNC via analysis of metabolites.

Results

Based on a middle cerebral artery occlusion (MCAO) rat model, the dynamic levels of amino acids in CSF 3, 6, 12, and 24 h after MCAO were analyzed. Up to 24 h, the accumulated nine AA biomarkers were found to significantly change in the MCAO group compared to the sham group and exhibited an obvious tendency for returning to baseline values after BNC treatment. In addition, based on the imbalanced network of CI, four key enzymes that regulate the generation of BNC-mediated AA biomarkers were selected and validated using an enzyme-linked immunosorbent assay and western blotting. Finally, aromatic-L-amino-acid decarboxylase (AADC) was found to be one of the putative targets for BNC-mediated protection against CI.

Conclusion

This study provides new strategies to explore the mechanism of cerebral ischemia and help discover the potential mechanism of BNC.

Alpha-Synuclein: From Early Synaptic Dysfunction to Neurodegeneration

Over the last two decades, many experimental and clinical studies have provided solid evidence that alpha-synuclein (α-syn), a small, natively unfolded protein, is closely related to Parkinson's disease (PD) pathology. To provide an overview on the different roles of this protein, here we propose a synopsis of seminal and recent studies that explored the many aspects of α-syn. Ranging from the physiological functions to its neurodegenerative potential, the relationship with the possible pathogenesis of PD will be discussed. Close attention will be paid on early cellular and molecular alterations associated with the presence of α-syn aggregates.

SB-334867 (an Orexin-1 Receptor Antagonist) Effects on Morphine-Induced Sensitization in Mice-a View on Receptor Mechanisms

The present study focused upon the role of SB-334867, an orexin-1 receptor antagonist, in the acquisition of morphine-induced sensitization to locomotor activity in mice. Behavioral sensitization is an enhanced systemic reaction to the same dose of an addictive substance, which assumingly increases both the desire for the drug and the risk of relapse to addiction. Morphine-induced sensitization in mice was achieved by sporadic doses (five injections every 3 days) of morphine (10 mg/kg, i.p.), while a challenge dose of morphine (10 mg/kg) was injected 7 days later. In order to assess the impact of orexin system blockade on the acquisition of sensitization, SB-334867 was administered before each morphine injection, except the morphine challenge dose. The locomotor activity test was performed on each day of morphine administration. Brain structures (striatum, hippocampus, and prefrontal cortex) were collected after behavioral tests for molecular experiments in which mRNA expression of orexin, dopamine, and adenosine receptors was explored by the qRT-PCR technique. Additionally, the mRNA expression of markers, such as GFAP and Iba-1, was also analyzed by the same technique. SB-334867 inhibited the acquisition of morphine-induced sensitization to locomotor activity of mice. Significant alterations were observed in mRNA expression of orexin, dopamine, and adenosine receptors and in the expression of GFAP and Iba-1, showing a broad range of interactions in the mesolimbic system among orexin, dopamine, adenosine, and glial cells during behavioral sensitization. Summing up, the orexin system may be an effective measure to inhibit morphine-induced behavioral sensitization.

Intermittent theta-burst stimulation rescues dopamine-dependent corticostriatal synaptic plasticity and motor behavior in experimental parkinsonism: Possible role of glial activity

BACKGROUND

Recent studies support the therapeutic utility of repetitive transcranial magnetic stimulation in Parkinson's disease (PD), whose progression is correlated with loss of corticostriatal long-term potentiation and long-term depression. Glial cell activation is also a feature of PD that is gaining increasing attention in the field because astrocytes play a role in chronic neuroinflammatory responses but are also able to manage dopamine (DA) levels.

METHODS

Intermittent theta-burst stimulation protocol was applied to study the effect of therapeutic neuromodulation on striatal DA levels measured by means of in vivo microdialysis in 6-hydroxydopamine-hemilesioned rats. Effects on corticostriatal synaptic plasticity were studied through in vitro intracellular and whole-cell patch clamp recordings while stepping test and CatWalk were used to test motor behavior. Immunohistochemical analyses were performed to analyze morphological changes in neurons and glial cells.

RESULTS

Acute theta-burst stimulation induced an increase in striatal DA levels in hemiparkinsonian rats, 80 minutes post-treatment, correlated with full recovery of plasticity and amelioration of motor performances. With the same timing, immediate early gene activation was restricted to striatal spiny neurons. Intense astrocytic and microglial responses were also significantly reduced 80 minutes following theta-burst stimulation.

CONCLUSION

Taken together, these results provide a first glimpse on physiological adaptations that occur in the parkinsonian striatum following intermittent theta-burst stimulation and may help to disclose the real potential of this technique in treating PD and preventing DA replacement therapy-associated disturbances. © 2017 International Parkinson and Movement Disorder Society.

Kinase-dependent Regulation of Monoamine Neurotransmitter Transporters

Modulation of neurotransmission by the monoamines dopamine (DA), norepinephrine (NE), and serotonin (5-HT) is critical for normal nervous system function. Precise temporal and spatial control of this signaling in mediated in large part by the actions of monoamine transporters (DAT, NET, and SERT, respectively). These transporters act to recapture their respective neurotransmitters after release, and disruption of clearance and reuptake has significant effects on physiology and behavior and has been linked to a number of neuropsychiatric disorders. To ensure adequate and dynamic control of these transporters, multiple modes of control have evolved to regulate their activity and trafficking. Central to many of these modes of control are the actions of protein kinases, whose actions can be direct or indirectly mediated by kinase-modulated protein interactions. Here, we summarize the current state of our understanding of how protein kinases regulate monoamine transporters through changes in activity, trafficking, phosphorylation state, and interacting partners. We highlight genetic, biochemical, and pharmacological evidence for kinase-linked control of DAT, NET, and SERT and, where applicable, provide evidence for endogenous activators of these pathways. We hope our discussion can lead to a more nuanced and integrated understanding of how neurotransmitter transporters are controlled and may contribute to disorders that feature perturbed monoamine signaling, with an ultimate goal of developing better therapeutic strategies.

Detection of biogenic amines in C57BL/6 mice brain by capillary electrophoresis electrokinetic supercharging

A facile, sensitive EKS/MEKD-PDAD method was developed for the detection of neurotransmitters in C57BL/6 mice brain.

Drug abuse and the neurovascular unit

Drug abuse continues to create a major international epidemic affecting society. A great majority of past drug abuse research has focused mostly on the mechanisms of addiction and the specific effects of substance use disorders on brain circuits and pathways that modulate reward, motivation, craving, and decision making. Few studies have focused on the neurobiology of acute and chronic substance abuse as it relates to the neurovascular unit (brain endothelial cell, neuron, astrocyte, microglia, and pericyte). Increasing research indicates that all cellular components of the neurovascular unit play a pivotal role in both the process of addiction and how drug abuse affects the brain response to diseases. This review will focus on the specific effects of opioids, amphetamines, alcohol, and nicotine on the neurovascular unit and its role in addiction and adaption to brain diseases. Elucidation of the role of the neurovascular unit on the neurobiology associated with drug addiction will help to facilitate the development of better therapeutic approaches for drug-dependent individuals.

Glia activation and its role in oxidative stress

Glia activation and neuroinflamation are major factors implicated in the aetiology of most neurodegenerative diseases (NDDs). Several agents and toxins have been known to be capable of inducing glia activation an inflammatory response; most of which are active substances that can cause oxidative stress by inducing production of reactive oxygen species (ROS). Neurogenesis on the other hand involves metabolic and structural interaction between neurogenic and glia cells of the periventricular zone (PVZ); a region around the third ventricle. This study investigates glia activation (GFAP), cell proliferation (Ki-67) and neuronal metabolism (NSE) during neurogenesis and oxidative stress by comparing protein expression in the PVZ against that of the parietal cortex. Adult Wistar Rats were treated with normal saline and 20 mg/Kg KCN for 7 days. The tissue sections were processed for immunohistochemistry to demonstrate glia cells (anti Rat-GFAP), cell proliferation (anti Rat-Ki-67) and neuronal metabolism (anti Rat-NSE) using the antigen retrieval method. The sections from Rats treated with cyanide showed evidence of neurodegeneration both in the PVZ and cortex. The distribution of glia cells (GFAP), Neuron specific Enolase (NSE) and Ki-67 increased with cyanide treatment, although the increases were more pronounced in the neurogenic cell area (PVZ) when compared to the cortex. This suggests the close link between neuronal metabolism and glia activation both in neurogenesis and oxidative stress.