Dopamine In Brain Tissue Research Articles

A novel approach to tyrosinase-based biosensors: Electrode reactions and biological measurement

This study introduces a novel tyrosinase-based biosensor designed to simultaneously detect tyrosinase, tyrosine, L-DOPA, and L-DOPA quinone. The biosensor, designated as GCE/GNP/Cys/Chit/Tyrase, was developed by immobilizing tyrosinase on a modified glassy carbon electrode (GCE) that incorporates electrodeposited gold nanoparticles, cysteine, and chitosan. The morphology of the biosensor was characterized using scanning electron microscopy (SEM). The electrochemical behaviors of the biosensor were explored in response to the target analytes. Key analytical characteristics were assessed, including linear range, sensitivity, selectivity, limits of detection and quantification, long-term stability, repeatability, reproducibility, electrochemically active surface area, and charge transfer behavior. The biosensor demonstrated a linear response range of 1–120 μM, with an impressive sensitivity of 200.4 mA.Lmol−1cm−2 and a detection limit of 27 μM. This study provides a comprehensive evaluation of the analytical features of tyrosinase-based biosensors. Additionally, the biosensor was applied to quantify dopamine in brain tissue, utilizing a calibration curve derived from the fabricated biosensor. The dopamine concentration measured in five Wistar rats was 35 ± 2.75 μM, reflecting the mean and standard deviation, respectively. These results confirm the biosensor's capability for accurately detecting this critical neurotransmitter in the brains of Wistar rats. This investigation underscores the potential of tyrosinase-based biosensors for diverse analytical applications in biological samples.

Comparison of dopamine release and uptake parameters across sex, species and striatal subregions.

For over four decades, fast-scan cyclic voltammetry (FSCV) has been used to selectively measure neurotransmitters such as dopamine (DA) with high spatial and temporal resolution, providing detailed information about the regulation of DA in the extracellular space. FSCV is an optimal method for determining concentrations of stimulus-evoked DA in brain tissue. When modelling diseases involving disturbances in DA transmission, preclinical rodent models are especially useful because of the availability of specialized tools and techniques that serve as a foundation for translational research. There is known heterogeneity in DA dynamics between and within DA-innervated brain structures and between males and females. However, systematic evaluations of sex- and species-differences across multiple areas are lacking. Therefore, using FSCV, we captured a broad range of DA dynamics across five sub-regions of the dorsal and ventral striatum of males and females of both rats and mice that reflect the functional heterogeneity of DA kinetics and dynamics within these structures. While numerous differences were found, in particular, we documented a strong, consistent pattern of increased DA transporter activity in females in all of the regions surveyed. The data herein are intended to be used as a resource for further investigation of DA terminal function.

Optimized Fabrication of Carbon-Fiber Microbiosensors for Codetection of Glucose and Dopamine in Brain Tissue.

Dopamine (DA) signaling is critically important in striatal function, and this metabolically demanding process is fueled largely by glucose. However, DA and glucose are typically studied independently and, as such, the precise relationship between DA release and glucose availability remains unclear. Fast-scan cyclic voltammetry (FSCV) is commonly coupled with carbon-fiber microelectrodes to study DA transients. These microelectrodes can be modified with glucose oxidase (GOx) to generate microbiosensors capable of simultaneously quantifying real-time and physiologically relevant fluctuations of glucose, a nonelectrochemically active substrate, and DA, which is readily oxidized and reduced at the electrode surface. A chitosan hydrogel can be electrodeposited to entrap the oxidase enzyme on the sensor surface for stable, sensitive, and selective codetection of glucose and DA using FSCV. This strategy can also be used to entrap lactate oxidase on the carbon-fiber surface for codetection of lactate and DA. However, these custom probes are individually fabricated by hand, and performance is variable. This study characterizes the physical nature of the hydrogel and its effects on the acquired electrochemical data in the detection of glucose (2.6 mM) and DA (1 μM). The results demonstrate that the electrodeposition of the hydrogel membrane is improved using a linear potential sweep rather than a direct step to the target potential. Electrochemical impedance spectroscopy data relate information on the physical nature of the electrode/solution interface to the electrochemical performance of bare and enzyme-modified carbon-fiber microelectrodes. The electrodeposition waveform and scan rate were characterized for optimal membrane formation and performance. Finally, codetection of both DA/glucose and DA/lactate was demonstrated in intact rat striatum using probes fabricated according to the optimized protocol. Overall, this work improves the reliable fabrication of carbon-fiber microbiosensors for codetection of DA and important energetic substrates that are locally delivered to the recording site to meet metabolic demand.

Processed Polygonatum cyrtonema Hua attenuates postpartum depression in rat model by regulating monoamines and hormones

BackgroundPolygonatum cyrtonema Hua is a traditional Chinese medicinal food herb which can regulate the liver and Qi, nourish the heart and blood, moisten the lungs and nourish the kidneys with the potential to treat emotional diseases. However, few studies have explored the effects of Polygonatum cyrtonema Hua on postpartum depression. Therefore, we investigated whether processed Polygonatum cyrtonema Hua could improve postpartum depression in rat models by regulating monoamines and hormones. MethodsFemale Sprague-Dawley rats were randomized into normal control (0.9%Nacl), Sham operation (0.9%Nacl), postpartum depression model (0.9%Nacl), fluoxetine (2.5 mg/kg Fluoxetine), low, medium and high dose of processed Polygonatum cyrtonema Hua (2.5 g/kg, 5 g/kg, 10 g/kg) groups. Rats in these groups received drug intervention, and then subjected to Open-field test and Forced swimming test. Brain tissues and serum samples were collected and used to quantify levels of monoamines, hypothalamic-pituitary-adrenal axis and serum Estradiol. The status of neuronal cells in hippocampus 1 region was examined through hematoxylin-eosin staining, whereas expression of estrogen receptor α and β was detected by immunohistochemistry. ResultsRats in the model group showed decreased mobility time, the disorder of neuronal cells in hippocampus 1 area, and decreased concentration of 5-hydroxytryptamine and dopamine in brain tissue, norepinephrine and estradiol in serum as well as estrogen receptor α and β expression. They also exhibited increased adrenocorticotropic hormone, corticosterone and corticotropin releasing hormone in serum. However, the treatment with processed Polygonatum cyrtonem Hua or fluoxetine reversed the above abnormalities. ConclusionThe H group showed significant improvement in postpartum depression in rats, and processed Polygonatum cyrtonema Hua can be used as a developing drug for the prevention or treatment of depression.

The glycine-containing dipeptide leucine-glycine raises accumbal dopamine levels in a subpopulation of rats presenting a lower endogenous dopamine tone

Interventions that elevate glycine levels and target the glycine receptor (GlyR) in the nucleus Accumbens (nAc) reduce ethanol intake in rats, supposedly by acting on the brain reward system via increased basal and attenuated ethanol-induced nAc dopamine release. Glycine transport across the blood brain barrier (BBB) appears inefficient, but glycine-containing dipeptides elevate whole brain tissue dopamine levels in mice. This study explores whether treatment with the glycine-containing dipeptides leucine-glycine (Leu-Gly) and glycine-leucine (Gly-Leu) by means of a hypothesized, facilitated BBB passage, alter nAc glycine and dopamine levels and locomotor activity in two rodent models. The acute effects of Leu-Gly and Gly-Leu (1–1000 mg/kg, i.p.) alone or Leu-Gly in combination with ethanol on locomotion in male NMRI mice were examined in locomotor activity boxes. Striatal and brainstem slices were obtained for ex vivo HPLC analyses of tissue levels of glycine and dopamine. Furthermore, the effects of Leu-Gly i.p. (1–1000 mg/kg) on glycine and dopamine output in the nAc were examined using in vivo microdialysis coupled to HPLC in freely moving male Wistar rats. Leu-Gly and Gly-Leu did not significantly alter locomotion, ethanol-induced hyperlocomotor activity or tissue levels of glycine or dopamine, apart from Gly-Leu 10 mg/kg that slightly raised nAc dopamine. Microdialysis revealed no significant alterations in nAc glycine or dopamine levels when regarding all rats as a homogenous group. In a subgroup of rats defined as dopamine responders, a significant elevation of nAc dopamine (20%) was seen following Leu-Gly 10–1000 mg/kg i.p, and this group of animals presented lower baseline dopamine levels compared to dopamine non-responders. To conclude, peripheral injection of glycine-containing dipeptides appears inefficient in elevating central glycine levels but raises accumbal dopamine levels in a subgroup of rats with a lower endogenous dopamine tone. The tentative relationship between dopamine baseline and ensuing response to glycinergic treatment and presumptive direct interactions between glycine-containing dipeptides and the GlyR bear insights for refinement of the glycinergic treatment concept for alcohol use disorder (AUD).

(Invited) Near Infrared Optical Probes for Imaging Neuromodulators with High Spatiotemporal Resolution

Dopamine neurotransmission plays critical roles in brain function in both health and disease and aberrations in dopamine neurotransmission are implicated in several psychiatric and neurological disorders, including schizophrenia, depression, anxiety, and Parkinson’s disease. Until recently, measuring the dynamics of dopamine and other neurotransmitters of this class could not be achieved at spatiotemporal resolutions necessary to understand how dopamine regulates the plasticity and function of neurons and neural circuits, and how dysfunctions in this regulation lead to disease. Probes that satisfy critical attributes in spatial and temporal resolution, and chemical selectivity are needed to facilitate investigations of brain neurochemistry.To address this need, we developed an ultrasensitive near-infrared “turn-on” nanosensor (nIRCat) for the catecholamines dopamine and norepinephrine and implemented nIRCat to study endogenous dopamine dynamics in brain tissue. nIRCats are synthesized from photostable and near infrared emissive functionalized single wall carbon nanotubes (SWCNT) and exhibit maximal relative change in fluorescence intensity (ΔF/F0) of up to 35-fold, with a dynamic range that spans physiological concentrations of their target brain analytes. We demonstrate that nIRCat can detect electrically and optogenetically evoked release of dopamine in brain tissue, revealing putative hotspots of activity that exhibited a log-normal distribution in size, ranging from 2 – 10 µm for mice brain tissue in the dorsomedial striatum. Furthermore, the synthetic nature of the molecular recognition platform afforded compatibility with dopamine-receptor targeting antipsychotics and psychoactive drugs and permitted studies of how such receptor-targeting drugs modulate evoked dopamine release. This assay revealed presynaptic correlates of drug activity at the level of putative dopamine release sites, which had heretofore been inaccessible to probe with existing tools. Our results suggest that nIRCat technology may uniquely support similar explorations of processes that regulate dopamine neuromodulation at the level of individual synapses, and exploration of the effects of receptor agonists and antagonists that are commonly used as psychiatric drugs as well as drugs that lead to substance use disorder. We conclude that SWCNTs can serve as versatile synthetic optical scaffolds for monitoring interneuronal chemical signaling in the brain extracellular space at spatial and temporal scales pertinent with the encoded neurochemical information.

(Invited) Near-Infrared Optical Probes for Imaging Neuromodulators with High Spatiotemporal Resolution

Dopamine neurotransmission plays critical roles in brain function in both health and disease and aberrations in dopamine neurotransmission are implicated in several psychiatric and neurological disorders, including schizophrenia, depression, anxiety, and Parkinson’s disease. Until recently, measuring the dynamics of dopamine and other neurotransmitters of this class could not be achieved at spatiotemporal resolutions necessary to understand how dopamine regulates the plasticity and function of neurons and neural circuits, and how dysfunctions in this regulation lead to disease. Probes that satisfy critical attributes in spatial and temporal resolution, and chemical selectivity are needed to facilitate investigations of brain neurochemistry.To address this need, we developed an ultrasensitive near-infrared “turn-on” nanosensor (nIRCat) for the catecholamines dopamine and norepinephrine and implemented nIRCat to study endogenous dopamine dynamics in brain tissue. nIRCats are synthesized from photostable and near infrared emissive functionalized single wall carbon nanotubes (SWCNT) and exhibit maximal relative change in fluorescence intensity (ΔF/F0) of up to 35-fold, with a dynamic range that spans physiological concentrations of their target brain analytes. We demonstrate that nIRCat can detect electrically and optogenetically evoked release of dopamine in brain tissue, revealing putative hotspots of activity that exhibited a log-normal distribution in size, ranging from 2 – 10 µm for mice brain tissue in the dorsomedial striatum. Furthermore, the synthetic nature of the molecular recognition platform afforded compatibility with dopamine-receptor targeting antipsychotics and psychoactive drugs and permitted studies of how such receptor-targeting drugs modulate evoked dopamine release. This assay revealed presynaptic correlates of drug activity at the level of putative dopamine release sites, which had heretofore been inaccessible to probe with existing tools. Our results suggest that nIRCat technology may uniquely support similar explorations of processes that regulate dopamine neuromodulation at the level of individual synapses, and exploration of the effects of receptor agonists and antagonists that are commonly used as psychiatric drugs as well as drugs that lead to substance use disorder. We conclude that SWCNTs can serve as versatile synthetic optical scaffolds for monitoring interneuronal chemical signaling in the brain extracellular space at spatial and temporal scales pertinent with the encoded neurochemical information.

LY354740 Reduces Extracellular Glutamate Concentration, Inhibits Phosphorylation of Fyn/NMDARs, and Expression of PLK2/pS129 α-Synuclein in Mice Treated With Acute or Sub-Acute MPTP.

Glutamate overactivity in basal ganglia critically contributes to the exacerbation of dopaminergic neuron degeneration in Parkinson’s disease (PD). Activation of group II metabotropic glutamate receptors (mGlu2/3 receptors), which can decrease excitatory glutamate neurotransmission, provides an opportunity to slow down the degeneration of the dopaminergic system. However, the roles of mGlu2/3 receptors in relation to PD pathology were partially recognized. By using mGlu2/3 receptors agonist (LY354740) and mGlu2/3 receptors antagonist (LY341495) in mice challenged with different cumulative doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), we demonstrated that systemic injection of LY354740 reduced the level of extracellular glutamate and the extent of nigro-striatal degeneration in both acute and sub-acute MPTP mice, while LY341495 amplified the lesions in sub-acute MPTP mice only. LY354740 treatment improved behavioral dysfunctions mainly in acute MPTP mice and LY341495 treatment seemed to aggravate motor deficits in sub-acute MPTP mice. In addition, ligands of mGlu2/3 receptors also influenced the total amount of glutamate and dopamine in brain tissue. Interestingly, compared with normal mice, MPTP-treated mice abnormally up-regulated the expression of polo-like kinase 2 (PLK2)/pS129 α-synuclein and phosphorylation of Fyn/N-methyl-D-aspartate receptor subunit 2A/2B (GluN2A/2B). Both acute and sub-acute MPTP mice treated with LY354740 dose-dependently reduced all the above abnormal expression. Compared with MPTP mice treated with vehicle, mice pretreated with LY341495 exhibited much higher expression of p-Fyn Tyr416/p-GluN2B Tyr1472 and PLK2/pS129 α-synuclein in sub-acute MPTP mice models. Thus, our current data indicated that mGlu2/3 receptors ligands could influence MPTP-induced toxicity, which supported a role for mGlu2/3 receptors in PD pathogenesis.

Nanosensors shine a light on brain chemistry

In diagnosing and treating neuropsychiatric and neurodegenerative diseases like depression, schizophrenia, and Parkinson’s disease, doctors rely on evaluating a patient’s symptoms rather than directly analyzing brain chemistry. Although a variety of tools can study the brain, they are too imprecise, indirect, or invasive to probe it at the molecular level. So chemists are developing optical sensors that they hope will provide a clearer picture of how symptoms relate to changes in brain chemistry. In this video, host Kerri Jansen explores a trend in probes sensing dopamine in brain tissue. The University of California, Berkeley’s Markita Landry shares her team’s progress with carbon nanotubes (Sci. Adv. 2019, DOI: 10.1126/sciadv.aaw3108). And Lin Tian from the University of California, Davis, gives us a glimpse of tools based on genetically modified proteins (Science 2018, DOI: 10.1126/science.aat4422). Learn more at cenm.ag/dopamine.

Possible Neuroprotective Effects of Crocin Against Motor and Neurochemical Changes in Rotenone Induced Animal Model of Parkinson's Disease

AbstractBackgropund: Parkinson's Disease (PD) is considered a second most common neurodegenerative disease with slow and irreversible nigrostriatal degeneration with subsequent motor and behavioral deficits. Oxidative stress plays a key role in the pathogenesis of PD. Rotenone is a common pesticide inducing PD by the generation of oxidative stress.Aim of Study: The aim of this study was to investigate the possible neuroprotective effects of crocin (saffron active compound) on rotenone induced Parkinson-like behaviors.Material and Methods: 70 male Wister Albino rats were divided into 7 groups (10) per each. (1) Control group (normal saline); (2) Crocin 40mg/Kg; (3) Polyethylene Glycol (PEG) group (vehicle of Levodopa); (4) Rotenone group; (5) Rotenone + crocin 20mg/Kg; (6) Rotenone + crocin 40mg/Kg; (7) Rotenone + Levodopa 10mg/Kg. All agents were injected intraperitoneally once a day for 4 weeks. The neurobehavioral tests include open field, descent latency time in the bar test (seconds), forepaw stride length (cm) and locomotor activity. In serum, the level of 8-hydroxydeoxyguanosine 8-OHdG was estimated. The level of Malondialdehyde (MDA), reduced glutathione (GSH), tumor necrosis factor alpha TNF-a, dopamine and nitrite/nitrate levels were measured in the brain tissue.Results: Rotenone induced neurobehavioral deficits with elevation of brain MDA, brain TNF-a, Nitrite/nitrate level and serum 8-OHdG and reduction of GSH, brain tissue dopamine. Crocin (20 or 40) improved these neurobehavioral deficits. Crocin (20 or 40) and L-DOPA decreased MDA, serum 8-OHdG, TNF-a and Nitrite/nitrate level and increased GSH and dopamine level. Crocin 40 had achieved potent effect compared with crocin 20.Conclusion: Rotenone induced Parkinson-like behavior in rats. Crocin achieved a protective effect through reducing lipid peroxidation, anti-inflammatory and reducing DNA damage together with improvement of neurobehavioral deficits.

POSSIBLE NEUROPROTECTIVE EFFECTS OF CROCIN AGAINST MOTOR AND NEUROCHEMICAL CHANGES IN ROTENONE INDUCED ANIMAL MODEL OF PARKINSON'S DISEASE

Parkinson’s disease (PD) is considered the second most common neurodegenerative disease with subsequent motor and behavioral deficits. Oxidative stress plays a key role in the pathogenesis of PD. AIM: The aim of this study was to investigate the possible neuroprotective effects of crocin on rotenone-induced Parkinson- like behaviors. MATERIALS M (2) Crocin 40 (10 rats); (3) Polyethylene glycol (PEG) (10 rats) ; (4) Rotenone (40 rats) injected I.P. of 1.5 mg/kg/48 hrs. for 2 weeks [11]; Preliminary behavioral tests and the rats that showed PD features were randomly subdivided into 4 equal groups of 10 rats per each. (4A) Rotenone-treated: (4B): Crocin 20 treated. (4C): Crocin 40 treated. (4D) L-DOPA treated- group. The neurobehavioral were done. In serum, the level of 8-hydroxydeoxyguanosine 8-OHdG was estimated. The level of malondialdehyde (MDA), reduced glutathione (GSH), tumor necrosis factor alpha TNF-α, dopamine, and nitrite/ nitrate levels were measured in the brain tissue. RESULTS: Rotenone induced neurobehavioral deficits with elevation of brain MDA, brain TNF- α, Nitrite/nitrate level and serum 8-OHdG and reduction of GSH, brain tissue dopamine. Crocin (20 or 40) improved these neurobehavioral deficits. Crocin (20 or 40) and L-DOPA decreased MDA, serum 8-OHdG, TNF- α and Nitrite/nitrate level and increased GSH and dopamine level. Crocin 40 had achieved potent effect compared with crocin 20. In summary, rotenone-induced Parkinson- like behavior in rats. Crocin achieved a protective effect

Dopaminergic Effects of Major Bath Salt Constituents 3,4-Methylenedioxypyrovalerone (MDPV), Mephedrone, and Methylone Are Enhanced Following Co-exposure.

Designer drug mixtures popularized as "bath salts" often contain the synthetic cathinones 3,4 methylenedioxypyrovalerone (MDPV), mephedrone, and methylone in various combinations. However, most preclinical investigations have only assessed the effects of individual bath salt constituents, and little is known about whether co-exposure to MDPV, mephedrone, and methylone produces significant neuropharmacological interactions. This study evaluated and compared how MDPV, mephedrone, and methylone influence discrete brain tissue dopamine (DA) levels and motor stimulant responses in mice when administered alone and as a ternary mixture. Male adolescent Swiss-Webster mice received intraperitoneal injections of saline or 1 or 10mg/kg doses of MDPV, mephedrone, or methylone, or a cocktail of all three cathinones at doses of 1, 3.3, or 10mg/kg each. The effect of each treatment on DA and DA metabolite levels in mesolimbic and nigrostriatal brain tissue was quantified 15min after a single exposure using HPLC-ECD. Additionally, locomotor activity was recorded in mice after acute (day 1) and chronic intermittent (day 7) dosing. MDPV, mephedrone, and methylone produced dose-related increases in mesolimbic and nigrostriatal DA levels that were significantly enhanced following their co-administration. In addition, mice treated with the cathinone cocktail displayed decreased locomotor activity on day 1 that was exacerbated by day 7 and not observed with any of the drugs alone. Our findings demonstrate a significant enhanced effect of MDPV, mephedrone, and methylone on both DA, and these effects on DA result in significant alterations in locomotor activity.

The Antioxidative Action of ZTP by Increasing Nrf2/ARE Signal Pathway.

So far, more than 25,000 brain diseases have been shown to be related to oxidative stress. Excessive free radicals and reactive oxygen species (ROS) can attack cells resulting in dysfunctional proteins, lipids, and nucleic acid, finally leading to imbalance of energy metabolism, cell death, gene mutation, and immune reaction. Therefore oxidative stress plays an important role in neuronal diseases. As a traditional Chinese medicine, Zhengtian Pill (ZTP) was reported to have the ability to reduce the blood viscosity of migraine model rats, with increased beta-endorphin, serotonin, adrenaline, and dopamine in brain tissue. Moreover ZTP can effectively accelerate blood circulation and attenuate blood coagulation. However, the molecular mechanisms of ZPT are still unclear. Through the behavioral test we found that ZTP can significantly improve depression-like behavior induced by LPS when rat was treated with ZTP (L 0.17 g/kg, M 0.34 g/kg, and H 0.7 g/kg) intraperitoneal injection once a day for 30 consecutive days. And ZTP can resist oxidative stress (>72 h) for a longer time. And ZTP can promote the levels of ATP and SOD and reduce the levels of ROS and MDA in the brain. At the same time, ZTP can have antioxidant stress through increasing the expression level of Nrf2/HO-1/P38. These results show that ZTP may be a potential antioxidant stress drug for variety of diseases associated with oxidative stress injury.

Impact of space allowance on performance traits, brain neurotransmitters and blood antioxidant activity of New Zealand White rabbits

The objective of this trial was to investigate the effect of space allowance on performance, welfare-related parameters and the levels of brain neurotransmitters in growing male rabbits. In a cage housing system, a total of 96 weaned rabbits were accommodated on three space allowance conditions (S1 = 1425 cm2/rabbit; S2 = 850 cm2/rabbit; S3 = 625 cm2/rabbit), with 8 replicate cages per each group. Rabbits in the S1 and S2 groups showed better daily feed intake and feed conversion ratio compared with the high stocking density group (p = 0.004 and 0.018, respectively). Compared to the highest stocking density group (S3), rabbits in the S1 and S2 groups showed significantly lower serum cortisol, MDA and GSSH level (p = 0.026, 0.018 and 0.009, respectively). The concentration of dopamine in brain tissues was significantly decreased in the S3 group compared with other experimental groups (P = 0.001). However, there was no significant effect of space allowance on the brain AChE level (P = 0.277). Brain serotonin and GABA levels showed a significant decrease in rabbits reared with a limited space allowance (S3) compared with S1 and S2 groups (P = 0.001 and 0.038, respectively). The level of brain MDA was significantly increased in the S3 group compared with the S1 group (P = 0.006). However, there were no detectable differences in the brain ATP level in rabbits reared with different space allowance (P = 0.693). In conclusion, the current study indicates that the 850 cm2/rabbit stocking density has resulted in a better feed intake, and welfare-related conditions compared with the 625 cm2/rabbit. Furthermore, the limited space allowance may impair the most important brain neurotransmitters in male rabbits.

A free-standing electrochemical sensor based on graphene foam-carbon nanotube composite coupled with gold nanoparticles and its sensing application for electrochemical determination of dopamine and uric acid

In this study, a free-standing electrochemical sensor based on 3D graphene foam (GF) with dense carbon nanotubes (CNTs) and gold nanoparticles (GNPs) was developed for the first time. The structure of this hybrid electrode (GF/CNTs/GNPs) was observed by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and transmission electron microscopy (TEM), and its electrochemical properties was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained sensor displayed outstanding electrocatalytic activity toward dopamine (DA) and uric acid (UA) compared with the commercial unmodified glass carbon electrode. Detection of DA and UA with the presented sensor yielded remarkable sensitivity of 12.72μAμM−1cm−2 and 3.36μAμM−1cm−2, the low detection limits of 1.36nM and 33.03nM (S/N=3), with wide linear range of 0.10–48μM and 0.50–60μM, respectively. Furthermore, quantification of DA in brain tissue and UA in human urine was realized and the results were found in good agreement with those obtained by using high performance liquid chromatography.

Optimization of combinations of ginsenoside-Rg1, ginsenoside-Rb1, evodiamine and rutaecarpine for effective therapy of mouse migraine.

Wuzhuyu decoction (WZYD) is a classic traditional Chinese medicine (TCM) formula. It has been extensively used for treating migraine for thousands of years in TCM. Four potential active ingredients from WZYD, ginsenoside-Rg1 (Rg1), ginsenoside-Rb1 (Rb1), evodiamine (Ev) and rutaecarpine (Ru), were found to have positive correlations with pharmacodynamic indicators involving mouse migraine in our previous study. To find a better therapeutic effect on migraine, this research was carried out to optimize the combinations of Rg1, Rb1, Ev and Ru using the uniform design method. The results showed that Rb1 and Ev played key roles in improving the therapeutic effect on mouse migraine by strongly ameliorating pharmacodynamic indicators associated with migraine. They significantly increased the contents of 5-hydroxytryptamine, noradrenaline and dopamine in brain tissues, and reduced the content of nitric oxide in brain tissues and the activities of nitric oxide synthase in both brain tissues and blood serum. The optimal concentrations of Rb1 and Ev were 1057.4 mg/L and 312.5 mg/L, respectively. Rg1 and Ru contributed less to the overall desirability, suggesting that they had reverse effects on some pharmacodynamic indicators of this type of migraine. The verification test demonstrated by the immunohistochemical method that the optimal combination inhibited the expression of c-fos and c-jun in periaqueductal gray of mice, and strongly ameliorated pharmacodynamic indicators. These results suggested that the therapeutic effect of the optimal combination of the four ingredients was strong, and the optimal results were proven to be reliable and accurate.

In vivo [11C]dihydrotetrabenazine binding in rat striatum: sensitivity to dopamine concentrations

The sensitivity of the in vivo binding of [(11)C]dihydrotetrabenazine ([(11)C]DTBZ) and [(11)C]methylphenidate ([(11)C]MPH) to their respective targets - vesicular monoamine transporter type 2 (VMAT2) and neuronal membrane dopamine transporter - after alterations in endogenous levels of dopamine was examined in the rat brain. In vivo binding of [(11)C]DTBZ and [(11)C]MPH was determined using a bolus+infusion protocol. The in vitro number of VMAT2 binding sites was determined by autoradiography. Repeated dosing with alpha-methyl-p-tyrosine (AMPT) at doses that significantly (-75%) depleted brain tissue dopamine levels resulted in increased (+36%) in vivo [(11)C]DTBZ binding to VMAT2 in the striatum. The increase in binding could be completely reversed via treatment with L-DOPA/benserazide to restore dopamine levels. There were no changes in the total number of VMAT2 binding sites, as measured using in vitro autoradiography. No changes were observed for in vivo [(11)C]MPH binding to the dopamine transporter in the striatum following AMPT pretreatment. These results indicate that large reductions in dopamine concentrations in the rat brain can produce modest but significant changes in the binding of radioligands to VMAT2, which can be reversed by replenishment of dopamine using exogenous L-DOPA.

Asymmetry in dopamine levels in the nucleus accumbens and motor preference in rats

Several studies on mice have demonstrated a correlation between the concentrations of dopamine and its metabolites in the nucleus accumbens and asymmetry in forelimb preference. Dopamine concentrations were greater in the nucleus accumbens ipsilateral in relation to the preferred paw. Limb preference was demonstrated in rats during performance of a response consisting of withdrawing food from a horizontal tube. Brain tissue dopamine concentrations were estimated by high-performance liquid chromatography with electrochemical detection. The results showed that in "left-handed" rats, the dopamine concentration in the left nucleus accumbens was significantly greater than that in "right-handed" rats. In right-handed rats, the dopamine concentration in the right nucleus accumbens was greater than that in the left. The results obtained here are significantly consistent with data obtained in mice and support the suggestion that the dopamine level in rats is greater in the nucleus accumbens ipsilateral to the preferred limb.

Real-time decoding of dopamine concentration changes in the caudate-putamen during tonic and phasic firing.

The fundamental process that underlies volume transmission in the brain is the extracellular diffusion of neurotransmitters from release sites to distal target cells. Dopaminergic neurons display a range of activity states, from low-frequency tonic firing to bursts of high-frequency action potentials (phasic firing). However, it is not clear how this activity affects volume transmission on a subsecond time scale. To evaluate this, we developed a finite-difference model that predicts the lifetime and diffusion of dopamine in brain tissue. We first used this model to decode in vivo amperometric measurements of electrically evoked dopamine, and obtained rate constants for release and uptake as well as the extent of diffusion. Accurate predictions were made under a variety of conditions including different regions, different stimulation parameters and with uptake inhibited. Second, we used the decoded rate constants to predict how heterogeneity of dopamine release and uptake sites would affect dopamine concentration fluctuations during different activity states in the absence of an electrode. These simulations show that synchronous phasic firing can produce spatially and temporally heterogeneous concentration profiles whereas asynchronous tonic firing elicits uniform, steady-state dopamine concentrations.

Dependence of dopamine calibration factors on media Ca 2+ and Mg 2+ at carbon-fiber microelectrodes used with fast-scan cyclic voltammetry

Carbon-fiber microelectrodes and voltammetric methods have been used extensively for the detection of dopamine in brain tissue in vivo and in vitro. Voltammetric microelectrodes are often calibrated in non-physiological media, like phosphate-buffered saline, rather than in oxygenated physiological media. Here, we determined dopamine calibration factors (nA μM −1) in several defined solutions for two types of carbon-fiber electrode used with fast-scan cyclic voltammetry. For both electrode types, dopamine calibration factors, and thus electrode sensitivities, were 2–3-fold higher in phosphate- or HEPES-buffered saline than in a bicarbonate-based artificial CSF (ACSF) that reflected that normal ionic composition of brain extracellular fluid. Removal of Ca 2+ and Mg 2+ from ACSF eliminated this difference. Because extracellular Ca 2+ concentration ([Ca 2+] o) can fall under stimulation conditions used to elicit dopamine release, we also evaluated the size of stimulated [Ca 2+] o shifts in guinea pig midbrain slices using ion-selective microelectrodes. The [Ca 2+] o decreases were less than 100 μM, which was well below the mM decreases observed to alter DA sensitivity. Consequently, calibration data obtained in normal physiological solutions should be valid under conditions of mild stimulation. Moreover, calibration in divalent cation-free media will cause calculated DA levels to be underestimated and should be avoided, unless appropriate for a given experimental paradigm.