Dopamine Values Research Articles

Ultrasensitive composite electrochemical sensor with printed wrinkled CNTs nanostructure for simultaneous detection

Combining biomimetic and 3D printing has created new opportunities for the manufacture of electrochemical sensors. Dopamine (DA) and Uric acid (UA) are common body electroactive substances, and their detection is important for diagnosing metabolic diseases. Metal electrochemical sensors have limitations in sensitivity and selectivity due to their smooth 2D structures, which make it challenging to capture comprehensive electrochemical information. Here, inspired by taste buds, an ultrasensitive CNT-Pt composite electrochemical sensor, including a printed biomimetic wrinkled CNTs film, was prepared for simultaneous detection of DA and UA. Nanoscale Pt electrode was prepared by UV-LIGA process and the wrinkled CNTs nanofilm was fabricated by thermally assisted electrohydrodynamic jet (E-Jet) printing. CNT lines of 3∼58 μm, droplets of 4 μm and 2D array structures have been printed. The enhanced sensing mechanism of wrinkled CNTs nanofilm was analyzed theoretically. The nanoscale wrinkled morphology (nanofolds∼50 nm) and hydrophilicity (CÃ20°) of printed wrinkled CNTs nanofilm were analyzed. The anodic peak potential for UA was observed to range from 0.429 V to 0.489 V for the conventional Pt electrochemical sensor, whereas it ranged from 0.205 V to 0.276 V for the CNT-Pt composite electrochemical sensor. The detection performance of CNT-Pt composite electrochemical sensor was improved by ∼40 % contrast with Pt electrochemical sensor. The prepared composite electrochemical sensor can effectively recognize DA, UA and AA. From analysis, the peak value of AA was not obvious, the peak values of DA and UA were 0.096 V and 0.265 V. The composite electrochemical sensor successfully eliminated the detection interference caused by AA in detecting DA and UA. The nanoscale composite electrochemical sensor and its hybrid manufacturing method provide great potential for electrochemical testing applications.

Research progress on the roles of dopamine and dopamine receptors in digestive system diseases.

Dopamine (DA) is a neurotransmitter synthesized in the human body that acts on multiple organs throughout the body, reaching them through the blood circulation. Neurotransmitters are special molecules that act as messengers by binding to receptors at chemical synapses between neurons. As ligands, they mainly bind to corresponding receptors on central or peripheral tissue cells. Signalling through chemical synapses is involved in regulating the activities of various body systems. Lack of DA or a decrease in DA levels in the brain can lead to serious diseases such as Parkinson's disease, schizophrenia, addiction and attention deficit disorder. It is widely recognized that DA is closely related to neurological diseases. As research on the roles of brain-gut peptides in human physiology and pathology has deepened in recent years, the regulatory role of neurotransmitters in digestive system diseases has gradually attracted researchers' attention, and research on DA has expanded to the field of digestive system diseases. This review mainly elaborates on the research progress on the roles of DA and DRs related to digestive system diseases. Starting from the biochemical and pharmacological properties of DA and DRs, it discusses the therapeutic value of DA- and DR-related drugs for digestive system diseases.

Dopamine alters phage morphology to exert an anti-infection effect.

Antiviral drug development is important for human health, and the emergence of novel COVID-19 variants has seriously affected human lives and safety. A bacteriophage-a bacterial virus with a small and simple structure-is an ideal experimental candidate for studying the interactions between viruses and their hosts. In this study, the effects and mechanisms of catecholamines on phages were explored, and dopamine (DA) was found to have general and efficient anti-infection effects. A clear dose-dependent effect was observed when different phages were treated with DA, with higher DA concentrations exhibiting stronger anti-phage activity. The half maximal inhibitory concentration values of DA for vB-EcoS-IME167, T4 Phage, and VMY22 were determined as 0.26, 0.12, and 0.73 mg mL-1, respectively. The anti-phage effect of DA increased with treatment duration. In addition, the anti-infection activities of DA against vB-EcoS-IME167, T4 Phage, and VMY22 were increased by 105, 104, and 104 folds compared to that of the control. This ability of DA was observed only in phages and not in the host bacteria. Morphological changes of phages were observed under transmission electron microscopy following their treatment with DA, and considerable changes in adsorption were confirmed via quantitative reverse transcription polymerase chain reaction. These results suggest that the anti-phage effect of DA is primarily due to the destruction of the external structure of the phage. This study, to the best of our knowledge, is the first to report the universal anti-phage infection effect of dopamine, which provides novel information regarding DA and forms a basis for further research and development of antiviral drugs. Moreover, it provides a new perspective for the research about the defense and counter-defense of bacteria and bacteriophages.

Stable and ligand-free gold nanoparticles produced by laser ablation as efficient electrocatalysts for electrochemical sensing of dopamine

The possibility of producing high-purity and ligand-free nanoparticles makes laser ablation in liquids (LAL) an interesting method to produce gold nanoparticles (AuNPs). AuNPs play an important role in the manufacture of electrochemical sensors due to their excellent electrical conductivity and chemical stability. In this study, stable and ligand-free AuNPs were produced by LAL (AuNP/LAL) using a nanosecond pulsed laser. The control of this single-step production was facilitated by adding sodium chloride (NaCl), resulting in the reduction of AuNPs size (10 ± 2 nm) and higher stability (monitored for 12 weeks). The potential of NaCl-stabilized AuNPs/LAL as modifiers agents were investigated for dopamine (DA) sensing by cyclic voltammetry for the first time. The novel electrochemical sensor (GCE/AuNPs.LAL/Nafion) achieved an increase in the peak current of ca. 3 and 6 times for oxidation and reduction, respectively. A comparison of chemical syntheses and LAL approaches was given for electrochemical sensing applications; the AuNPs/LAL showed to be more efficient in facilitating the electronic transfer and electrocatalytic reactions. The estimated limit of detection values for DA sensing was 0.77 µmol/L (oxidation) and 1.08 µmol/L (reduction). The method hereby proposed is promising for clinical applications as the new electrochemical sensor allowed proper sensitivity for DA.

An ultra-sensitive dopamine measurement platform based on molecularly imprinted polymer-carbon hybrid nanomaterials for in vitro use

In the present study, we designed an ultrasensitive sensing platform for the evaluation of the physiologically relevant values of basal dopamine (DA) in a culture medium as a complex biological environment. The proposed sensing platform was fabricated via the integration of molecular imprinting technology with carbon hybrid nanomaterials. Carbon nanofibers (CNFs) were grown by using plasma-enhanced chemical vapor deposition (PECVD) on tetrahedral amorphous carbon (ta-C) thin films on silicon wafers. The prepared ta-C/CNFs sensing platforms were electrochemically coated with DA-imprinted polypyrrole as the molecularly imprinted polymer (MIP) or "artificial receptors". The three-dimensional MIP receptors were able to determine trace values of DA in phosphate-buffered saline solution (PBS) pH 7.4 (LOD = 5.43 nM) as well as in the absolute culture media such as DMEM/F-12 medium (LOD = 39 nM), DMEM/F-12 medium supplemented with 15% horse serum and 2.5% fetal bovine serum (LOD = 53.26 nM), and F-12 K cell culture medium (LOD = 62.57 nM), with highly physiologically relevant sensitivity and free of interference by other coexisting biomolecules and biological compounds. As all the fabrication steps of the composite electrode are compatible with common microsystem technology processes, the present results pave the way for integrating these ultra-sensitive electrodes to microelectrode arrays (MEA) platforms used for human dopaminergic neurons studies in vitro and enable continuous measurement of the basal DA concentration in real-time for instance in organoid studies.

Graphene Quantum Dot‐poly(L‐lysine)‐gold Nanoparticles Nanocomposite for Electrochemical Determination of Dopamine and Serotonin

AbstractA nanocomposite consists of AuNPs, GQD, and poly(L‐lysine) was prepared for highly sensitive electrochemical determination of dopamine (DA) and serotonin (5‐HT) neurotransmitters which are of vital importance in neurological disorders. The P(L‐Lys) GQD was successfully obtained a one‐step co‐electrodeposition of GQD and L‐Lys on the PGE. The electrochemical behaviors of DA and 5‐HT were analyzed via DPV and CV. LOD values for DA and 5‐HT were calculated as 0.03 μM and 0.017 μM, respectively. Also, the DA and 5‐HT contents were determined at the PGE/AuNPs/P(L‐Lys)‐GQD in fetal bovine serum samples and pharmaceutical formulations, and high recovery values were obtained.

Bio-assisted preparation of efficiently architectured nanostructures of \u03b3-Fe2O3 as a molecular recognition platform for simultaneous detection of biomarkers

Magnetic nanoparticles of iron oxide (γ-Fe2O3) have been prepared using bio-assisted method and their application in the field of biosensors is demonstrated. Particularly in this work, different nanostructures of γ-Fe2O3 namely nanospheres (NS), nanograsses (NG) and nanowires (NW) are prepared using a bio-surfactant namely Furostanol Saponin (FS) present in Fenugreek seeds extract through co-precipitation method by following “green” route. Three distinct morphologies of iron oxide nanostructures possessing the same crystal structure, magnetic properties, and varied size distribution are prepared and characterized. The resultant materials are analyzed using field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, vibrating sample magnetometer and Fourier transform infrared spectroscopy. Moreover, the effect of reaction time and concentration of FS on the resultant morphologies of γ-Fe2O3 nanostructures are systematically investigated. Among different shapes, NWs and NSs of γ-Fe2O3 are found to exhibit better sensing behaviour for both the individual and simultaneous electrochemical detection of most popular biomarkers namely dopamine (DA) and uric acid (UA). Electrochemical studies reveal that γ-Fe2O3 NWs showed better sensing characteristics than γ-Fe2O3 NSs and NGs in terms of distinguishable voltammetric signals for DA and UA with enhanced oxidation current values. Differential pulse voltammetric studies exhibit linear dependence on DA and UA concentrations in the range of 0.15–75 µM and 5 μM – 0.15 mM respectively. The detection limit values for DA and UA are determined to be 150 nM and 5 µM. In addition γ-Fe2O3 NWs modified electrode showed higher sensitivity, reduced overpotential along with good selectivity towards the determination of DA and UA even in the presence of other common interferents. Thus the proposed biosensor electrode is very easy to fabricate, eco-friendly, cheaper and possesses higher surface area suggesting the unique structural patterns of γ-Fe2O3 nanostructures to be a promising candidate for electrochemical bio-sensing and biomedical applications.

Chemically versus electrochemically reduced graphene oxide: Improved amperometric and voltammetric sensors of phenolic compounds on higher roughness surfaces

The electrochemistry of hydroquinone (HQ), catechol (CT), and dopamine (DP) on a glassy-carbon electrode (GCE) modified with chemically (CRGO) and electrochemically reduced graphene oxide (ERGO) was investigated and compared for the development of amperometric and voltammetric sensors. Cyclic voltammetric measurements showed higher current on the CRGO-modified GCE, which can be explained by the higher number of sheets compared with ERGO-modified as revealed by SEM images as well as higher roughness surface monitored by AFM, indicating a higher electroactive area. Electrochemical impedance spectroscopy (EIS) revealed that both modified surfaces presented a very similar behavior (Nyquist plots) and lower resistance to electron transfer in comparison with the unmodified GCE. Considering both modified electrodes for sensing purposes, differential-pulse voltammetry (DPV) in unstirred solutions and amperometry under hydrodynamic solutions showed higher sensitivity and lower limit of detection (LOD) values for HQ, CT and DP on the CRGO-modified GCE. These results indicate that the effect of surface rugosity and electroactive area of RGO modified electrodes contribute to the improvement of sensing characteristics of phenolic compounds using either DPV or amperometric detection under flow conditions. DPV and amperometry provided LOD values between 1 and 5nmolL−1 and 12 and 55nmolL−1, respectively, while the latter offers much faster responses resulting in theoretical analytical frequency higher than 1000h−1.

Catecholamine levels in a Ramadan fasting model in rats: a case control study

ABSTRACTEating habits as well as physical exercise are very important for a healthy lifespan. Ramadan-type fasting, which is food and water avoidance during the daylight period for four weeks, has drawn attention due to its positive impacts on metabolism and health. The aim of this study was to compare the blood and urine catecholamine (CA) levels in fasting and non-fasting rats, in terms of stress response. A total of 20 male rats were randomly divided into a fasting group and a control group. Four weeks later, blood and urine samples were taken after decapitation. Analysis of CAs was done using high-performance liquid chromatography with florescence detection (HPLC-FLD). The dopamine (DA), adrenaline (ADR) and noradrenaline (NA) blood and urine concentrations were found to be higher in the fasting group compared to the control group, but the difference was statistically significant only for the blood DA levels (p < 0.05). In the fasting group, the blood values of ADR and NA correlated with each other but not with the DA levels, whereas there was correlation among the urine levels of DA, ADR and NA. In the control group, the blood and urine values of DA, ADR and NA correlated with each other. The differences observed in the blood and urine CAs indicate a specific regulation of CAs in Ramadan-type fasting, which needs to be investigated thoroughly in future studies.

Differential contribution of lipoxygenase isozymes to nigrostriatal vulnerability

The 5- and 12/15-lipoxygenase (LOX) isozymes have been implicated to contribute to disease development in CNS disorders such as Alzheimer’s disease. These LOX isozymes are distinct in function, with differential effects on neuroinflammation, and the impact of the distinct isozymes in the pathogenesis of Parkinson’s disease has not as yet been evaluated. To determine whether the isozymes contribute differently to nigrostriatal vulnerability, the effects of 5- and 12/15-LOX deficiency on dopaminergic tone under naïve and toxicant-challenged conditions were tested. In naïve mice deficient in 5-LOX expression, a modest but significant reduction (18.0% reduction vs. wildtype (WT)) in striatal dopamine (DA) was detected (n=6–8 per genotype). A concomitant decline in striatal tyrosine hydroxylase (TH) enzyme was also revealed in null 5-LOX vs. WT mice (26.2%); however, no changes in levels of DA or TH immunoreactivity were observed in null 12/15-LOX vs. WT mice. When challenged with the selective dopaminergic toxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), WT mice showed a marked reduction in DA (31.9%) and robust astrocytic and microglial activation as compared to saline-treated animals. In contrast, null 5-LOX littermates demonstrated no significant striatal DA depletion or astrogliosis (as noted by Western blot analyses for glial acidic fibrillary protein (GFAP) immunoreactivity). In naïve null 12/15-LOX mice, no significant change in striatal DA values was observed compared to WT, and following MPTP treatment, the transgenics revealed striatal DA reduction similar to the challenged WT mice. Taken together, these data provide the first evidence that: (i) LOX isozymes are involved in the maintenance of normal dopaminergic function in the striatum and (ii) the 5- and 12/15-LOX isozymes contribute differentially to striatal vulnerability in response to neurotoxicant challenge.

Increased affinity of dopamine for D2‐like versus D1‐like receptors. Relevance for volume transmission in interpreting PET findings

Evidence indicates that dopamine (DA) mainly acts as a volume transmission (VT) transmitter through its release into the extracellular fluid where the D(1) -like and D(2) -like receptors are predominantly extrasynaptic. It was therefore of interest to compare the affinities of the two major families of DA receptors. [(3)H] raclopride /DA and [(3)H] SCH23390/DA competition assays compared the affinity of DA at D(2) -like and D(1) -like receptors in rat dorsal striatal membrane preparations as well as in membrane preparations from CHO cell lines stably transfected with human D(2L) and D(1) receptors. The IC(50) values of DA at D(2) -like receptors in dorsal striatal membranes and CHO cell membranes were markedly and significantly reduced compared with the IC(50) values of DA at D(1) -like receptors. These IC(50) values reflect differences in both the high and low affinity states. The K(iH) value for DA at [(3)H] raclopride-labeled D(2) -like receptors in dorsal striatum was 12 nM, and this can help explain PET findings that amphetamine-induced increases in DA release can produce an up to 50% decrease of [(11)C] raclopride binding in the dorsal striatum in vivo. These combined results give indications for the existence of striatal D(2) -like receptor-mediated DA VT at the local circuit level in vivo. The demonstration of a K(iH) value of 183 nM for DA at D(1) antagonist-labeled D(1) -like receptors instead gives a likely explanation for the failure of a reduction of D(1) -like receptor binding after amphetamine-induced DA release in PET studies using the D(1) -like antagonist radioligands [(11)C] SCH23390 and [(11)C] NNC. It seems difficult to evaluate the role of the extrasynaptic D(1) receptors in VT in vivo with the PET radioligands available for this receptor.

The role of bromine adlayer at palladium electrode in the electrochemical oxidation of dopamine in alkaline solution

A palladium electrode modified with bromine monolayer was fabricated throughout a spontaneous oxidative chemisorption of bromide ions contained in an alkaline solution. The surface coverage and the apparent double layer capacitance induced by the adsorption of bromide ions under the present applied potential indicates the formation of incomplete monolayer due to a prominent co-adsorption of hydroxyl ions (OH −). The film modified electrode exhibited a substantial reactivity and high sensitivity in the electrochemical oxidation of dopamine (DA) in the presence of ascorbic acid (AA) and uric acid (UA). This trend was attributed to the structure and the composition of the bromine adlayer which renders a partial negative charge capable of attracting selectively the cationic DA and repelling anionic AA and UA. The peak currents of DA in the binary and ternary mixtures were well-separated, well-defined and increased linearly with respect to its concentration. The interference property expected by the presence of both AA and UA has been advantageously eliminated at the bromine-adlayer modified electrode. The apparent diffusion coefficient value of DA was 1.37 × 10 −8 m 2 s −1, based on an amperometric current–time study. The present system provides a simple and fundamental approach for the simultaneous and selective determination of DA in the presence of AA and UA.

Determination of dansylated monoamine and amino acid neurotransmitters and their metabolites in human plasma by liquid chromatography–electrospray ionization tandem mass spectrometry

The determination of neurotransmitters (NTs) and their metabolites facilitates better understanding of complex neurobiology in the central nervous system disorders and has expanding uses in many other fields. We present a liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI/MS/MS) method for the quantification of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), vanillymandelic acid (VMA), 3-methoxy-4-hydroxy phenylglycol (MHPG), 5-hydroxytryptamine (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), glutamate (Glu), and γ-aminobutyric acid (GABA). The NTs and their metabolites were dansylated and analyzed by an LC gradient on a C18 column on-line with a tandem mass spectrometer. This method exhibited excellent linearity for all of the analytes with regression coefficients higher than 0.99. The lower limit of quantification (LLOQ) values for DA, DOPAC, HVA, NE, VMA, MHPG, 5-HT, 5-HIAA, Glu, and GABA were 0.57, 0.37, 0.35, 0.40, 0.35, 0.91, 0.27, 0.43, 0.65, and 1.62 pmol/ml, respectively. The precision results were expressed as coefficients of variation (CVs), ranging from 1.5% to 13.6% for intraassay and from 2.9% to 13.7% for the interassay. This novel LC–ESI/MS/MS approach is precise, highly sensitive, specific, and sufficiently simple. It can provide an alternative method for the quantification of the NTs and their metabolites in human plasma.

Neurotransmitter levels in the hypothalamus during postnatal development of rats.

The content of norepinephrine (NE), epinephrine (E), dopamine (DA) and serotonin (5-HT) in the rat hypothalamus was determined at four hours time interval during 24 hours period at the age of 12, 23, 27 and 75 days. It was found that the content of NE in the hypothalamus is low in 12 day-old rats, and during the postnatal period a gradual increase of NE was noted. The content of E in the hypothalamus is low in 12- to 27-day-old rats and an important increase was found in adult animals. The high values of DA and 5-HT concentration were found in the hypothalamus of 12-day-old rats and a transient decrease of 5-HT and DA at the age of 23 days was noted, further an important increase of the content of both neurotransmitters in the hypothalamus was demonstrated later in life. The presence of circadian rhythm of hypothalamic NE, E, DA and 5-HT content was found in 12-, 23-, 27-day-old and in adult rats overfed or underfed during the suckling period. However, no significant correlation was observed between the NE and E levels in the hypothalamus and the diurnal fluctuations of plasma corticosterone concentrations. In adult animals an inverse correlation between the plasma corticosterone level and hypothalamic 5-HT content was noted. In young 12- and 23-day-old rats the correlation between 5-HT in the hypothalamus and corticosterone in the plasma was positive. These results indicate that the shift of peak in plasma corticosterone levels during postnatal ontogenesis of rats observed in previous experiments is not dependent on the changes in diurnal fluctuation of hypothalamic neurotransmitter concentrations.

Local noradrenaline depletion elicits enhanced dopamine activity in the medial prefrontal cortex

Event Abstract Back to Event Local noradrenaline depletion elicits enhanced dopamine activity in the medial prefrontal cortex Rita Galosi1*, Attila Toth1, Zoltan Petyko1 and László Lénárd1 1 Hungarian Academy of Sciences , Medical School of University Pecs, Hungary Earlier data showed coupling between dopamine (DA) and noradrenaline (NA) release in the prefrontal cortex. In the present experiments, bilateral neurochemical lesions were carried out to destroy NA terminals in the medial prefrontal cortex (mPFC). In loco injection of 6-hydroxy-DOPA (6-OHDOPA) was applied. In other group, a potent DA uptake inhibitor, GBR12935 was injected before the administration of neurotoxin 6-hydroxy-dopamine (6-OHDA), which acts on both DA and NA terminal. DA and NA contents of the mPFC were determined by HPLC-electrochemical detection post mortem and in vivo. In controls, NA and DA values were 346.21 +/- 36.02 ng/g and 133.29 +/-21.61 ng/g wet weight tissue (average ± s.e.m.), respectively. GBR 12935 treatment alone did not show significant alteration in catecholamine levels. Lesions of NA terminals by 6-OHDOPA depleted the NA level only by 21 % [p<0.05]. 6-OHDOPA lesion caused elevated DA levels by 122 % [p<0.01]. Concentration of NA was reduced by 43 % [p<0.01] do to GBR 12935 + 6-OHDA lesion. The DA levels were elevated in these cases by 195 % [p<0.01]. Extracellular NA and DA concentrations were 4.36 +/- 1.03 and 5.32 +/- 0.7 pg/20μl sample, respectively. NA concentration was no detectable after GBR 12935 + 6-OHDA lesion. Baseline DA concentrations were enhanced [p<0.05]. Local reverse microdialysis of Yohimbine (10μM) α2 antagonist enhanced NA and DA level in the mPFC. Increase in DA concentration was higher following neurochemical lesion of NA terminals [p<0.01]. In summary, decreased NA input enhanced DA activity in the mPFC. This study was supported by ETT 317/2006, NKTH-OTKA K68431 and by the Hungarian Academy of Sciences. Conference: 12th Meeting of the Hungarian Neuroscience Society, Budapest, Hungary, 22 Jan - 24 Jan, 2009. Presentation Type: Poster Presentation Topic: Research on the cerebral cortex and related structures Citation: Galosi R, Toth A, Petyko Z and Lénárd L (2009). Local noradrenaline depletion elicits enhanced dopamine activity in the medial prefrontal cortex. Front. Syst. Neurosci. Conference Abstract: 12th Meeting of the Hungarian Neuroscience Society. doi: 10.3389/conf.neuro.01.2009.04.193 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 06 Mar 2009; Published Online: 06 Mar 2009. * Correspondence: Rita Galosi, Hungarian Academy of Sciences , Medical School of University Pecs, Pecs, Hungary, rita.galosi@aok.pte.hu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Rita Galosi Attila Toth Zoltan Petyko László Lénárd Google Rita Galosi Attila Toth Zoltan Petyko László Lénárd Google Scholar Rita Galosi Attila Toth Zoltan Petyko László Lénárd PubMed Rita Galosi Attila Toth Zoltan Petyko László Lénárd Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Plasma dopamine in workers exposed to urban stressor

The aim of this study is to evaluate if the occupational exposure to urban stressor could cause alterations in dopamine (DA) plasma levels and related diseases in traffic police officers compared to a control group. After excluding subjects with principal confounding factors, 306 traffic police officers (139 female and 167 male) and 301 controls (134 female and 167 male) were included in the study. In traffic police officers, mean DA values were significantly higher compared with controls (P = 0.006 and P = 0.000 in male and female, respectively). The distribution of DA values in traffic police officers and controls was significant (P = 0.000 and P = 0.000 in male and female, respectively). The number of male traffic police officers with a positive response to the questionnaire's items concerning anxiety, depression and panic attacks was higher than controls, though not significant (7.2% traffic police officers versus 4.2% controls). This difference was also not significant in female traffic police officers compared with controls. According to our previous researches on other neuro-immune-endocrine parameters, DA could be used as an early biological marker, valuable for the group to be employed in occupational sets, even before the onset of pathology.

Toxic effects of methoxychlor on the episodic prolactin secretory pattern: possible mediated effects of nitric oxide production.

BackgroundThis work addresses the issue of whether methoxychlor (MTX) exposure may modify the ultradian secretion of prolactin through changes in the synthesis of nitric oxide (NO) induced by Nω-nitro-L-arginine methyl ester (L-NAME) in the hypothalamic-pituitary axis. Associated changes in dopamine (DA) content in the anterior (AH), mediobasal (MBH) and posterior hypothalamus (PH) and median eminence (ME) were evaluated.MethodsTwo groups of animals (MTX and MTX+L-NAME treated) received subcutaneous (sc) injections of MTX at a dose of 25 mg/kg/day for one month. The other two groups of animals (control and L-NAME treated) received sc vehicle injections (0.5 mL/day of sesame oil), during the same period of time to be used as controls. Forty hours before the day of the experiment, animals were anaesthetized with intrapritoneal injections of 2.5% tribromoethanol in saline and atrial cannulas were implanted through the external jugular vein. Plasma was continuously extracted in Hamilton syringes coupled to a peristaltic bomb in tubes containing phosphate-gelatine buffer (to increase viscosity). The plasma was obtained by decantation and kept every 7 minutes for the measurement of plasma prolactin levels through a specific radioimmnunoassay and DA concentration by high-pressure liquid chromatography (HPLC).ResultsProlactin release in animals from all experimental groups analyzed was episodic. Mean plasma prolactin levels during the bleeding period, and the absolute pulse amplitude were increased after MTX or Nω-nitro-L-arginine methyl ester (L-NAME) administration. However MTX and L-NAME did not modify any other parameter studied with the exception of relative pulse amplitude in MTX treated rats. L-NAME administration to rats treated with the pesticide reduced mean plasma prolactin levels and the absolute amplitude of prolactin peaks. Peak duration, frequency and relative amplitude of prolactin peaks were not changed in the group of rats treated with MTX plus L-NAME as compared to either control or MTX treated rats. Whereas MTX decreased DA content in the ME and increased it in the AH, its content did not change in the MBH or PH, as compared to the values found in controls. Also, L-NAME administration decreased DA content in the ME as compared to controls. However, L- NAME administration to MTX exposed rats, markedly increased DA content in the ME as compared to either MTX treated or control rats. L-NAME administration increased DA content in the AH as compared to the values found in non-treated rats. However L-NAME administration to MTX exposed rats did not modify DA content as compared to either MTX treated or control rats. L-NAME administration did not modify DA content at the MBH nor in saline treated nor in MTX treated rats. However, the values of DA in the MBH in MTX plus L-NAME treated animals were statistically decreased as compared to L-NAME treated rats. In the PH, L-NAME administration increased DA content as compared to the values found in non-treated animals. L-NAME administration to MTX exposed rats also increased DA content as compared to either MTX treated or control rats.ConclusionThe results suggest the existence of an interaction between MTX and L-NAME in the modulation of the ultradian prolactin secretion at the pituitary levels. The possibility of an indirect effect mediated by changes in DA content at the ME requires further examination.

Ultra Micro Quantification of Dopamine and Homovanillic Acid in Human Brain Tissue: Quest for Higher Recovery and Sensitivity with CoulArray HPLC‐ECD System

Dopamine (DA), a biogenic amine neurotransmitter is involved in regulating a number of functions of the central and peripheral nervous systems, including voluntary and involuntary motor functions and cognitive behaviors. Since the concentration of dopamine in different parts of the brain is extremely small and decreases further in neurodegenerative diseases, such as HIV‐1 infection, a highly sensitive and specific methodology is required to quantify DA and its metabolite, homovanillic acid (HVA) in small weights of tissues from different regions of the brain. The method presented in this report used a highly sensitive multielectrode CoulArray HPLC‐ECD system for quantification of <4 pg of DA and <10 pg of HVA in homogenates of human brain tissues. A linear relationship in the calibration curves was observed between a wide range of concentration of standards of DA (50–500 pg/mL) and HVA (0.1–20.0 ng/mL) and the corresponding response factors. Separate aliquots from the same pool of brain tissue homogenate were used to extract DA and HVA by their specific extraction procedure and were quantified separately. Recovery of both DA and HVA from homogenate preparation and aqueous extraction were in the range of 88–98%. Stability of the system is evident from the consistency of retention times of analytes in different experiments. The reliability of the method is shown from the reproducibility of the values of DA and HVA obtained in different aliquots of the brain tissue homogenates.

Application of triple-probe microdialysis for fast pharmacokinetic/pharmacodynamic evaluation of dopamimetic activity of drug candidates in the rat brain

The technique of microdialysis utilizing three simultaneously implanted probes in the anaesthetized rat enables monitoring of pharmacokinetic (PK) profiles of a tested drug both in blood (1st probe) and brain (2nd probe) compartments and the pharmacodynamic (PD) response of neurotransmitters (3rd probe) released into, or accumulating within the brain extracellular fluid (ECF). In the present study, the PK/PD characteristics of cocaine (psychostimulant, strong abuse potential) and methylphenidate (dopamimetic drug without reinforcing properties) and two novel NeuroSearch (NS) drug candidates, NS-A and NS-B, were examined in blood and brain microdialysates from the anaesthetized rats. The extracellular levels of dopamine (DA) were monitored in the striatum or prefrontal cortex. The NS-A compound entered the brain ECF at a slightly slower rate then methylphenidate; however, both compounds showed about the same effect on the speed of accumulation of extracellular DA concentrations, which gradually increased to about 450% of the basal, predrug levels at the end of the sampling period (180 min). The NS-B compound showed more rapid PK profiles than those observed after methylphenidate and NS-A. The concentrations of NS-B reached the maximal values already 40 min after its administration, while at that time, the corresponding DA values were still unchanged. In fact, the increase in DA concentrations was about two times slower when compared to that of methylphenidate or NS-A-drugs. Faster kinetics of NS-B and its delayed effect on extracellular DA suggests that this compound is metabolized to an active intermediate product, which itself exerts stronger dopamimetic activity in the rat prefrontal cortex that the original NS-B substance. The present study illustrates the feasibility of triple-probe microdialysis to monitor the rate of extracellular accumulation of a drug candidate and DA levels in vivo and compare the resulting PK/PD profiles to those obtained for cocaine and methylphenidate. These measures may serve as initial neurochemical indicators of potential psychomimetic or reinforcing properties of the tested substances.

Changes of prolactin regulatory mechanisms in aging: 24-h rhythms of serum prolactin and median eminence and adenohypophysial concentration of dopamine, serotonin, (γ-aminobutyric acid, taurine and somatostatin in young and aged rats

Twenty-four hour rhythmicity of serum prolactin and median eminence and anterior pituitary content of dopamine (DA), serotonin (5HT), γ-aminobutyric acid (GABA), taurine and somatostatin were examined in 2 months-old and 18–20 months-old Wistar male rats. The concentration of prolactin was higher in aged rats, with peaks in both groups of rats at the early phase of the activity span. Median eminence DA content of young rats attained its maximum at the middle of rest span and decreased as prolactin levels augmented while the lowest values of adenohypophysial DA were observed at the time of prolactin peak. DA rhythmicity disappeared in aged rats. GABA content of median eminence and adenohypophysis was lower in aged rats, with maximal values of median eminence GABA at light-dark transition in young rats and at the second half of activity span in aged rats. Serum prolactin correlated positively with median eminence GABA in young rats and negatively with pituitary GABA in young and aged rats. Median eminence somatostatin peaked at the beginning of the activity phase (young rats) or at the end of the rest phase (aged rats). Prolactin levels and somatostatin content correlated significantly in young rats only. Median eminence and pituitary 5HT and taurine content did not change with age. The results indicate disruption of prolactin regulatory mechanisms with aging in rats.