DOPAC Research Articles

Heat Stress Modulates Brain Monoamines and Their Metabolites Production in Broiler Chickens Co-Infected with Clostridium perfringens Type A and Eimeria spp.

Heat stress has been related to the impairment of behavioral and immunological parameters in broiler chickens. However, the literature is not clear on the involvement of neuroimmune interactions in a heat stress situation associated with bacterial and parasitic infections. The present study evaluated the production of monoamines and their metabolites in brain regions (rostral pallium, hypothalamus, brain stem, and midbrain) in broiler chickens submitted to chronic heat stress and/or infection and co-infection with Eimeria spp. and Clostridium perfringens type A. The heat stress and avian necrotic enteritis (NE) modulated the neurochemical profile of monoamines in different areas of the central nervous system, in particular, those related to the activity of the hypothalamus-hypophysis-adrenal (HPA) axis that is responsible for sickness behavior. C. perfringens and/or Eimeria infection, heat stress increased 5-hydroxytryptamine (5-HT), 4,4 dihydroxyphenylacetic acid (DOPAC), and DOPAC/dopamine (DA) in the rostral pallium; 3-methoxy-4-hydroxyphenylethylene glycol (MHPG), homovanillic acid (HVA), HVA/DA, DOPAC/DA, and 5-hydroxyindoleacetic acid (5-HIAA)/5-HT in the hypothalamus; MHPG, 5-HIAA/5-HT, DOPAC/DA, and HVA/DA in the midbrain; and MHPG, DOPAC, HVA, HVA/DA, DOPAC/DA, and 5-HIAA/5-HT in the brainstem. Heat stress decreased noradrenaline + norepinephrine (NOR + AD) in all brain regions analyzed; 5-HT in the hypothalamus, midbrain, and brainstem; and DA in the midbrain. The results also showed the existence and activity of the brain-gut axis in broiler chickens. The brain neurochemical profile and corticosterone production are consistent with those observed in chronic stressed mammals, in animals with sickness behavior, and an overloading of the HPA axis.

The reactivity of dopamine precursors and metabolites towards ABTS•-: An experimental and theoretical study

The antiradical activity of L-3,4-dihydroxyphenylalanine (L-DOPA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid and tyrosine towards 2,2?-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt radical (ABTS?-) was investigated experimentally and theoretically by UV?Vis spectroscopy and the DFT theory. The importance of the catechol moiety for this reaction was proven due to the formation of intramolecular hydrogen bond in the formed anions and radicals. The results indicated L-DOPA and DOPAC were more potent radical scavengers than homovanillic acid and tyrosine just because of intramolecular hydrogen bond formation. Based on experimental spectra, it was proved that electron transfer led to the reduction of ABTS?-. The values of thermodynamic parameters were used to predict the preferred mechanism. The reaction rates were calculated for the electron transfer processes and it was shown that these were both kinetically and thermodynamically driven processes. Based on the reaction rate values, thermodynamic parameters, and present species, as determined by electronic spectra, it was concluded that single proton loss electron transfer (SPLET) is the dominant reaction mechanism in the investigated system.

Trehalose Neuroprotective Effects on the Substantia Nigra Dopaminergic Cells by Activating Autophagy and Non-canonical Nrf2 Pathways.

Trehalose, as a natural disaccharide, is known as an autophagy inducer. The neuroprotective effects of trehalose in the rat model of Parkinson′s disease were the aim of the present study. Parkinson′s disease model was induced by injecting 6-hydroxydopamine (6-OHDA) in the striatum of male Wistar rats. Apomorphine-induced behavior and substantia nigra neuronal counts were applied to evaluate the neuroprotective effects of trehalose. The autophagy was studied using the expression of p62 and LC3II/LC3I ratio. In addition, the antioxidant effects of trehalose were assessed by analyzing the levels of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and also glutathione reductase (GR), glutathione peroxidase (GPx) and Catalase (CAT) enzymes. Moreover, the levels of 3, 4-dihydroxyphenylacetic acid (DOPAC) and dopamine (DA) were assessed.The behavioral test showed that trehalose in the treatment group reduced the damage to the substantial nigra dopaminergic neurons, which was characterized by improved motor and reduced rotations in the treatment group as compared with the lesion group. In the histological examinations of the treatment group, trehalose prevented the destruction of dopaminergic neurons. Trehalose treatments increased autophagy (high LC3II/LC3I ratio) and the expression of the p62 protein as well. Through p62-dependent manner, it led to increased nuclear translocation of Nrf2 transcription factor and elevated expression of downstream antioxidant enzymes, such as GR, GPx, and CAT, restoring DA and DOPAC contents of the cells. In the current study, trehalose simultaneously protects substantia nigra dopaminergic cells by activating both non-canonical p62/SQSTM1-Keap1-Nrf2 and autophagy pathways.

The time course of changes in the state of monoaminergic systems in the brain of mice under the acute hypoxia with hypercapnia

In socially isolated male outbred albino mice, the changes of monoaminergic systems under acute hypoxia with hypercapnia were studied. In cerebral cortex, hippocampus and striatum of the right and left sides of the brain, the concentrations of norepinephrine, dopamine, serotonin and their metabolites - dihydroxyphenylacetic, homovanillic and 5-hydroxyindoleacetic acids were investigated using the HPLC method. In isolated mice, which were not subjected to hypoxia with hypercapnia, higher levels of dopamine and serotonin in the left cortex were found. There was no asymmetry in monoamines and their metabolites in other studied brain structures. 10 min after the onset of exposure, acute hypoxia with hypercapnia resulted in a right-sided increase in norepinephrine levels and a decrease in dopamine levels in the striatum and serotonin levels in the hippocampus. In the cerebral cortex, 10 min after of hypoxic exposure beginning, there was a left-sided decrease in the dopamine content, while the original asymmetry found in the cortex of intact animals disappeared. In isolated mice perished of hypoxia with hypercapnia, almost all parameters returned to the control level. The exception was the ratio of serotonin metabolite level to the neurotransmitter, which in the right cortex became lower than in control animals. In white outbred mice, the brain monoaminergic systems are suggested to be relatively resistant to the negative consequences of hypoxia and hypercapnia, and corresponding shifts resulting in the reflex brain response to changes in the gas composition of the respiratory air.

Plasma catecholamine levels in the early stages of treatment-naïve Parkinson’s disease

Rationale: Parkinson's disease (PD) is a neurodegenerative disorder with predominant involvement of catecholamine-producing neurons of the central and peripheral nervous system. Taking into account the relative availability and low costs of plasma catecholamine measurements, it is worthwhile to study these parameters as biomarkers of the early stages of PD.Aim: To determinate whether plasma levels of dopamine (DA), norepinephrine (NE), L-3,4-dihydroxyphenylalanine (DOPA) and dihydroxyphenylacetic acid (DOPAC) in patients with early stages of PD are related with akinetic-rigid and tremor-dominant variants and to compare the results to healthy volunteers.Materials and methods: This was an observational cross-sectional cohort study performed from 2012 to 2015. The main study group included unselected outpatients who attended the Republican Consultative and Diagnostic Center of Movement Disorders and Botulinotherapy (Kazan, Russia) with newly diagnosed early PD (Hoehn and Yahr stages I and II, 1967), of various ages and both genders, who had not been given any specific antiparkinsonian treatment. The control group included healthy volunteers with no clinical signs of PD (they could have other chronic diseases of the non-extrapyramidal origin). Plasma catecholamine levels were measured by gas liquid chromatography.Results: One hundred and thirty (130) treatment-naïve patients with newly diagnosed PD (mean age 59.34 ± 8.42 years, male gender 45.38%) were enrolled into the main study group. The control group included 56 healthy volunteers matched for age and gender. The distribution of various PD forms and stages was as follows: PD tremor-dominant variant 56.9%, PD akinetic-rigid variant 43.1%; PD stage I 76.9%, PD stage II 23.1%. Irrespective of the variant and stage, the PD patients demonstrated decreased NE levels, compared to the controls (95% confidence intervals 124–216 and 248–428 pg/mL, respectively, р < 0.026). DOPA plasma level was reduced only in the patients with akinetic-rigid PD variant (р = 0.017), while DOPAC level in the patients with PD stage II (р = 0.008). The average DA:NE:DOPA:DOPAC ratio was 1:32:105:64 in the control group, 1:62:238:88 in the patients with PD tremor-dominant variant (the difference is significant for NE and DOPA, р < 0.05), and 1:29:96:32 in those with PD akinetic-rigid variant (p > 0.05). In the healthy controls the changes in DOPA levels account for 84% of the DA and NE variability; no correlation between DOPAC and other catecholamines was found. On the contrary, in the PD patients regardless of the stage and the disease variant, DOPAC levels directly correlated with DA (p < 0.04). The PD tremor-dominant variant patients demonstrated a direct correlation between plasma NE and DOPA levels (p < 0.05).Conclusion: The results obtained on absolute and relative parameters catecholamine turnover in the patients with early PD stages support the hypothesis on different pathophysiology of the tremor-dominant and akinetic-rigid variants of PD.

Effects of Kisspeptin-10 on Hypothalamic Neuropeptides and Neurotransmitters Involved in Appetite Control.

Besides its role as key regulator in gonadotropin releasing hormone secretion, reproductive function, and puberty onset, kisspeptin has been proposed to act as a bridge between energy homeostasis and reproduction. In the present study, to characterize the role of hypothalamic kisspeptin as metabolic regulator, we evaluated the effects of kisspeptin-10 on neuropeptide Y (NPY) and brain-derived neurotrophic factor (BDNF) gene expression and the extracellular dopamine (DA), norepinephrine (NE), serotonin (5-hydroxytriptamine, 5-HT), dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIIA) concentrations in rat hypothalamic (Hypo-E22) cells. Our study showed that kisspeptin-10 in the concentration range 1 nM–10 μM was well tolerated by the Hypo-E22 cell line. Moreover, kisspeptin-10 (100 nM–10 μM) concentration independently increased the gene expression of NPY while BDNF was inhibited only at the concentration of 10 μM. Finally, kisspeptin-10 decreased 5-HT and DA, leaving unaffected NE levels. The inhibitory effect on DA and 5-HT is consistent with the increased peptide-induced DOPAC/DA and 5-HIIA/5-HT ratios. In conclusion, our current findings suggesting the increased NPY together with decreased BDNF and 5-HT activity following kisspeptin-10 would be consistent with a possible orexigenic effect induced by the peptide.

The Effect of Acute Hypoxia with Hypercapnia on the Monoamine Content in Symmetrical Brain Areas of Albino Mice

Changes in the activity of monoaminergic systems of the left and right hemispheres of the brain were investigated in male albino mice after acute hypoxia with hypercapnia. The concentrations of dopamine (DA), serotonin (5-HT) and their metabolites dihydroxyphenylacetic (DOPAC), homovanillic (HVA), and 5-hydroxyindoleacetic (5-HIAA) acids were measured by HPLC in the brain cortex, hippocampus, and striatum of the right and the left hemispheres. In the control mice (which were not exposed to hypoxia with hypercapnia), a higher concentration of DA in the left cortex was detected. No asymmetry in the content of other substances was identified in the investigated structures. Acute hypoxia with hypercapnia led to the right-sided increase of DA and 5-HT levels and to the left-sided reduction DOPAC in the cerebral cortex. Under the condition of hypoxia with hypercapnia, the left-sided increase of the DA content was detected in the hippocampus. In the striatum the contents of monoamines and their metabolites were insignificantly changed. It has been concluded that acute hypoxia with hypercapnia causes asymmetric changes in monoaminergic systems of the archicortex and the neocortex.

Dopamine Receptor Subtypes Mediate Opposing Effects on Form Deprivation Myopia in Pigmented Guinea Pigs.

We reported previously that changes in dopamine receptor (DR) subtype activation modulate spontaneous myopia progression in albino guinea pigs. To determine if DR control of refractive error development is different than in its normal counterpart, we evaluated the contribution of dopaminergic pathways to emmetropization and form deprivation myopia (FDM) progression in pigmented guinea pigs. Monocular myopia was induced by unilateral form-deprivation (FD). The effects of agonists of D1R (SKF38393) and D2R (quinpirole), the corresponding antagonists (SCH23390 and sulpiride), and vehicle were tested by peribulbar injection around FD or untreated control eyes. High-performance liquid chromatography with electrochemical detection quantified retinal and vitreous dopamine (DA) and 4-dihydroxyphenylacetic acid (DOPAC) levels. Ocular refraction and axial dimensions were measured using eccentric infrared photoretinoscopy (EIR) and A-scan ultrasonography, respectively, initially and after 2 or 4 weeks of treatment. After treatment with any of these four agents for 2 weeks, retinal and vitreal DA and DOPAC levels were not significantly different in drug- and vehicle-treated eyes. Neither agonism nor antagonism of D1R or D2R activity affected emmetropization. In contrast, D1R activation by SKF38393 inhibited FDM progression, while D2R activation by quinpirole augmented this response. On the other hand, D2R antagonism with sulpiride slowed FDM progression while D1R antagonism with SCH23390 had no effect. In pigmented guinea pigs, D1R activation inhibited, whereas D2R activation enhanced, FDM. These results closely mirror previous findings in albino animals and offer further evidence that DA and its cognate receptors affect refractive error regulation in guinea pigs.

Upgraded Methodology for the Development of Early Diagnosis of Parkinson's Disease Based on Searching Blood Markers in Patients and Experimental Models.

Numerous attempts to develop an early diagnosis of Parkinson's disease (PD) by searching biomarkers in biological fluids were unsuccessful. The drawback of this methodology is searching markers in patients at the clinical stage without guarantee that they are also characteristic of either preclinical stage or prodromal stage (preclinical-prodromal stage). We attempted to upgrade this methodology by selecting only markers that are found both in patients and in PD animal models. HPLC and RT-PCR were used to estimate the concentration of amino acids, catecholamines/metabolites in plasma and gene expression in lymphocytes in 36 untreated early-stage PD patients and 52 controls, and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice at modeling the clinical ("symptomatic") stage and preclinical-prodromal ("presymptomatic") stage of PD. It was shown that among 13 blood markers found in patients, 7 markers are characteristic of parkinsonian symptomatic mice and 3 markers of both symptomatic and presymptomatic mice. According to our suggestion, the detection of the same marker in patients and symptomatic animals indicates adequate reproduction of pathogenesis along the corresponding metabolic pathway, whereas the detection of the same marker in presymptomatic animals indicates its specificity for preclinical-prodromal stage. This means that the minority of markers found in patients-decreased concentration of L-3,4-dihydroxyphenylalanine (L-DOPA) and dihydroxyphenylacetic acid (DOPAC) and increased dopamine D3 receptor gene expression-are specific for preclinical-prodromal stage and are suitable for early diagnosis of PD. Thus, we upgraded a current methodology for development of early diagnosis of PD by searching blood markers not only in patients but also in parkinsonian animals.

Study on a dSPE-LC-MS/MS method for lysophosphatidylcholines and underivatized neurotransmitters in rat brain tissues

A dispersed solid phase extraction method for high performance liquid chromatography-tandem mass spectrometry analysis of lysophosphatidylcholines and underivatized neurotransmitters in rat brain tissues has been developed. Lysophosphatidylcholines (16:0, 18:0, 18:1, 20:4, 22:6), dopamine, 5-hydroxytryptamine, glutamine, dihydroxy-phenyl acetic acid, 5-hydroxyindole acetic acid and γ-aminobutyric acid were included. Dispersed solid phase extraction method was developed with the aiming to minimize the matrix effects. The cleanup procedure has been followed by rat brain homogenate, nitrogen blow drying, reconstitution, dispersive solid phase extraction and separation. Type and size of sorbent, the re-dissolving solution of the tissues, dilute solution, elution solution and the appropriate acidic or alkaline environment of the system were optimized for the purpose of obtaining a minimized matrix effect. Reversed-phase liquid chromatography was used for separation and mass spectrometry with multiple reaction monitoring was used for quantification. Electrospray ionization in negative ion mode was suitable for dihydroxy-phenyl acetic acid and 5-hydroxyindole acetic acid, while the other substances were detected in positive ion mode. The method was validated with linear range, method detection limit, limit of quantitation, matrix effects, relative recovery and the intra and inter-day precision. Linear range was at 0.1–1000 ng/mL for γ-aminobutyric acid and glutamine, 1.0–1000 ng/mL for dopamine, 10–1000 ng/mL for 5-hydroxytryptamine, 50–1000 ng/mL for 5-hydroxyindole acetic acid, dihydroxy-phenyl acetic acid and lysophosphatidylcholines. The mean matrix effect was between 52.48% and 123.12% and the CVs ranged from 0.41% to 10.96%. Mean relative recovery was from 65.17% to 114.89%, and the CVs ranged from 0.14% to 8.68% at 3 concentration levels for all compounds. Intra-day precision was with coefficients of variation between 0.20% and 14.7%. Inter-day precision values varied <9.21%, with coefficients of variation between 0.18% and 9.21%. The developed method was used to quantify lysophosphatidylcholines and underivatized neurotransmitters in healthy rat brain tissues in this study.

Monoaminergic and aminoacidergic receptors are involved in the antidepressant-like effect of ginsenoside Rb1 in mouse hippocampus (CA3) and prefrontal cortex

Ginsenoside Rb1 (Rb1), as the major bioactive ingredient of Panax ginseng C.A. Meyer, elicited a novel antidepressant-like effect in the forced swim test (FST) in chronic unpredictable mild stress (CUMS) rats in our previous study. To further explore the molecular mechanism of Rb1 on the neurotransmitters such as 5-hydroxytryptamine (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), norepinephrine (NE), dopamine (DA), homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), glutamate (Glu) and gamma-aminobutyric acid (GABA) in this antidepressant-like effect, the neurochemical changes in the monoaminergic and aminoacidergic receptors were investigated in the present pharmacological study by using reuptake inhibitors, receptors agonists and antagonists. The results showed that a sub-effective dose of Rb1 (5 mg/kg, p.o.) co-administered with fluoxetine (1 mg/kg, i.p., a selective serotonin reuptake inhibitor), reboxetine (2.5 mg/kg, i.p., a noradrenalin reuptake inhibitor), bupropion (10 mg/kg, i.p., a dopaminergic reuptake inhibitor), Mk-801 (0.05 mg/kg, i.p., an N-methyl-d-aspartic acid (NMDA) receptor antagonist) or baclofen (0.1 mg/kg, i.p., a selective GABA agonist) significantly decreased the immobility time in the FST. In addition, pretreating mice with NAN190 (0.5 mg/kg, i.p., a 5-HT1A receptor antagonist), ketanserin (5 mg/kg, i.p., a 5-HT2A/2C receptor antagonist), ondansetron (1 mg/kg, i.p., a 5-HT3A receptor antagonist), prazosin (1 mg/kg, i.p., an α1-adrenoceptor antagonist), yohimbine (1 mg/kg, i.p., an α2-adrenoceptor antagonist), SCH23390 (0.05 mg/kg, i.p., a selective D1 receptor antagonist), haloperidol (0.2 mg/kg, i.p., a non-selective D2 receptor antagonist), NMDA (75 mg/kg, i.p., an agonist at the glutamate site) or bicuculline (4 mg/kg, i.p., a competitive GABA antagonist) reversed the antidepressant-like effect of Rb1 (10 mg/kg, p.o.) in the FST. The results obtained for the neurotransmitters in the mouse hippocampus (CA3) and prefrontal cortex showed that Rb1 up-regulated the levels of 5-HT, 5-HIAA, NE, DA, and GABA and decreased the level of Glu. However, there were no significant differences in HVA or DOPAC. Furthermore, there were no significant alterations in the total path of spontaneous locomotor activity in all treatments. These results suggest that both monoaminergic (serotonergic, noradrenergic and dopaminergic) and aminoacidergic (glutamatergic and GABAergic) receptors may be involved in the antidepressant-like effect of Rb1.

Effect of oligochitosan-coated silver nanoparticles (OCAgNPs) on the growth and reproduction of three species Phytophthora in vitro

Phytophthora diseases cause billions of dollars annually in damage to crops. Nanotechnology provides various metallic nanoparticles exhibiting a strong activity against microbial pathogens. Silver nanoparticles-based products are outstanding samples, which has been produced in large scale and performed well with a high activity against several fungal pathogens. Our previous study indicated oligochitosan-coated silver nanoparticles (OCAgNPs) which were prepared from 3,4 dihydroxyphenyl acetic acid – conjugated oligochitosan and silver nitrate salt performed an enhancement in antibacterial ability at a very low concentration. Objective of this study was to determine the effect of the OCAgNPs on growth and reproduction of Phytophthora capsici, P. nicotianae and P. colocasiae in vitro. The study shown that strong inhibition of mycelial growth, sporangium production, zoospore release and zoospore germination of P. capsici, P. nicotianae and P. colocasiae occurred when exposed to at 9 ppm of OCAgNP. The results demonstrated a great potential of OCAgNPs for controlling growth of Phytophthora.

Suppression of Cisplatin-Induced Vomiting by Cannabis sativa in Pigeons: Neurochemical Evidences.

Cannabis sativa (CS, family Cannabinaceae) has been reported for its anti-emetic activity against cancer chemotherapy-induced emesis in animal models and in clinics. The current study was designed to investigate CS for potential effectiveness to attenuate cisplatin-induced vomiting in healthy pigeons and to study the impact on neurotransmitters involved centrally and peripherally in the act of vomiting. High-performance liquid chromatography system coupled with electrochemical detector was used for the quantification of neurotransmitters 5-hydroxytryptamine (5HT), dopamine (DA) and their metabolites; Di-hydroxy Phenyl Acetic acid (Dopac), Homovanillic acid (HVA), and 5-hydroxy indole acetic acid (5HIAA) centrally in specific brain areas (area postrema and brain stem) while, peripherally in small intestine. Cisplatin (7 mg/kg i.v.) induce emesis without lethality across the 24 h observation period. CS hexane fraction (CS-HexFr; 10 mg/kg) attenuated cisplatin-induced emesis ∼ 65.85% (P < 0.05); the reference anti-emetic drug, metoclopramide (MCP; 30 mg/kg), produced ∼43.90% reduction (P < 0.05). At acute time point (3rd h), CS-HexFr decreased (P < 0.001) the concentration of 5HT and 5HIAA in the area postrema, brain stem and intestine, while at 18th h (delayed time point) CS-HexFr attenuated (P < 0.001) the upsurge of 5HT caused by cisplatin in the brain stem and intestine and dopamine in the area postrema. CS-HexFr treatment alone did not alter the basal neurotransmitters and their metabolites in the brain areas and intestine except 5HIAA and HVA, which were decreased significantly. In conclusion the anti-emetic effect of CS-HexFr is mediated by anti-serotonergic and anti-dopaminergic components in a blended manner at the two different time points, i.e., 3rd and 18th h in pigeons.

Development of a diagnostic method for Parkinson's disease by reverse-phase high-performance liquid chromatography coupled with integrated pulsed amperometric detection

We developed a diagnostic method for Parkinson's disease by simultaneously analyzing biogenic amines and their metabolites using reverse-phase high-performance liquid chromatography coupled with integrated pulsed amperometric detection (RP-HPLC-IPAD) method. Dopamine (DA), 3, 4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), 5-hydroxyindolacetic acid (5-HIAA), and homovanillic acid (HVA) were used as biomarkers to diagnose Parkinson's disease. All target components were detected with good sensitivity using sodium hydroxide (as a post-column eluent). The limit of detection (S/N = 3) and limit of quantification (S/N = 10) of the target components ranged from 0.020 to 2.400 ng and from 0.080 to 8.000 ng, respectively. The coefficients of linear regression ranged from 0.9996 to 1.0000, all inter-day and intra-day precision values were <3.43%, and the average recovery and RSD ranged from 97.55 to 103.60% and 0.22 to 4.79% for mice striatum samples. This method exhibited good selectivity, sensitivity, and reproducibility and can be used directly without any pretreatment steps. Our method will be useful as a tool to diagnose Parkinson’s disease.

Endothelins and dopamine levels in tears for assessment of neurovascular disorders in glaucoma

To estimate the possibility of detection of neurovascular ocular disorders in glaucoma by assessing the content of catecholamines and endothelins in lacrimal fluid. The study included 47 patients with primary open-angle glaucoma (POAG). Tear eluate was analyzed by high performance liquid chromatography (HPLC) for catecholamines concentrations, and enzyme-linked immunoassay (ELISA) was used for evaluation of endothelins content. Endothelin-1 (ET-1) and big endothelin (bET) content in tears of patients with POAG was higher than in healthy controls. Concentration of dopamine (DA) in tears was lower and concentrations of L-dioxyphenylalanine and dihydroxyphenylacetic acid had a tendency for decrease. Noradrenaline content was equal in patients with POAG and controls. Adrenaline was not detected in any tear samples. Multidirectional changes of endothelins and DA levels in tears of patients with POAG was found. The increased concentration of ET-1 and its precursor bET promote vasoconstriction and decrease of aqueous humor outflow. The decrease of DA concentration is typical for neurodegenerative processes. Estimation of DA and endothelins concentrations in tears can enable early detection of neurovascular disorders in glaucoma patients and help evaluate their severity.

Inhibition of microRNA-200a Upregulates the Expression of Striatal Dopamine Receptor D2 to Repress Apoptosis of Striatum via the cAMP/PKA Signaling Pathway in Rats with Parkinson’s Disease

Parkinson's disease (PD) is a neurodegenerative movement disease with a high annual incidence. Accumulating evidence demonstrates that microRNAs play important roles in the pathogenesis of multiple neurological disorders, including PD. This study aims to investigate how microRNA-200a (miR-200a) regulates striatal dopamine receptor D2 (DRD2) to affect apoptosis of striatum in rats with PD and to explore the associated mechanism. After successfully establishing a PD model by 6-hydroxydopamine injections, PD rats were mainly treated with miR-200a mimics, inhibitors, Forskolin or a combination of miR-200a inhibitors and Forskolin. High-performance liquid chromatography-electrochemical detection (HPLC-ECD) was employed to detect the levels of dopamine, 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and chemistry colorimetric methods were applied to detect the levels of malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). A TUNEL assay and immunocytochemical staining were performed to observe apoptosis and tyrosine hydroxylase (TH)-positive cells in the striatum. The expression of miR-200a, DRD2, Bad, Bax, Bcl-2, cAMP and PKA was determined by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot assays. In the cellular experiments, after transfection with the inhibitor of miR-200a, decreased levels of Bax, GSH-Px, SOD, dopamine, DOPAC and HVA but increased levels of MDA and Bcl-2 were found along with a reduced apoptosis rate and increased TH-positive cell number. In addition, downregulating miR-200a resulted in lower expression of AKT, cAMP and PKA but higher expression of DRD2 and CREB, indicating that the downregulation of miR-200a increases DRD2 expression, which blocks the cAMP/PKA signaling pathway. This study provides evidence that the inhibition of miR-200a can repress apoptosis in the striatum via inhibition of the cAMP/PKA signaling pathway by upregulating DRD2 expression in PD rats.

The effect of acute hypoxia with hypercapnia on the content of monoamines in symmetrical areas of the brain in albino mice

Changes in the activity of monoaminergic systems of the left and right hemispheres of the brain after acute hypoxia with hypercapnia were investigated in male albino mice. The concentrations of dopamine (DA), serotonin (5-HT) and their metabolites dihydroxyphenylacetic (DOPAC), homovanilic (HVA) and 5-hydroxyindolacetic (5-HIAA) acids were measured by HPLC in the brain cortex, hippocampus and striatum of the right and the left hemispheres. In the control mice not exposed to hypoxia with hypercapnia, a higher concentration of DA in the left cortex was detected. No asymmetry in the content of other substances has been identified in the investigated structures. Acute hypoxia with hypercapnia led to the right-sided increase of DA and 5-HT levels and to the left-sided reduction DOPAC in the cerebral cortex. Under the condition of hypoxia with hypercapnia, in the hippocampus, the left-sided increase of the DA content was revealed. In the striatum the contents of monoamines and their metabolites were insignificantly changed. It has been concluded that acute hypoxia with hypercapnia causes asymmetric changes in monoaminergic systems of the archicortex and the neocortex.

Finasteride inhibited brain dopaminergic system and open-field behaviors in adolescent male rats.

Finasteride inhibits the conversion of testosterone to dihydrotestosterone. Because androgen regulates dopaminergic system in the brain, it could be hypothesized that finasteride may inhibit dopaminergic system. The present study therefore investigates the effects of finasteride in adolescent and early developmental rats on dopaminergic system, including contents of dopamine and its metabolites (dihydroxy phenyl acetic acid and homovanillic acid) and tyrosine hydroxylase expressions both at gene and protein levels. Meanwhile, open-field behaviors of the rats are examined because of the regulatory effect of dopaminergic system on the behaviors. Open-field behaviors were evaluated by exploratory and motor behaviors. Dopamine and its metabolites were assayed by liquid chromatography-mass spectrometry. Tyrosine hydroxylase mRNA and protein expressions were determined by real-time qRT-PCR and western blot, respectively. It was found that in adolescent male rats, administration of finasteride at doses of 25 and 50mg/kg for 14days dose dependently inhibited open-field behaviors, reduced contents of dopamine and its metabolites in frontal cortex, hippocampus, caudate putamen, nucleus accumbens, and down-regulated tyrosine hydroxylase mRNA and protein expressions in substantia nigra and ventral tegmental area. However, there was no significant change of these parameters in early developmental rats after finasteride treatment. These results suggest that finasteride inhibits dopaminergic system and open-field behaviors in adolescent male rats by inhibiting the conversion of testosterone to dihydrotestosterone, and imply finasteride as a potential therapeutic option for neuropsychiatric disorders associated with hyperactivities of dopaminergic system and androgen.

Antagonistic effect of dopamine structural analogues on human GABA\u03c11 receptor

GABAergic and dopaminergic pathways are co-localized in several areas of the central nervous system and recently several reports have shown co-release of both neurotransmitters. The GABA-A receptor (β and ρ1 subunits) is modulated by dopamine (DA) and, interestingly, GABAρ1 can be modulated by several biogenic amines. Here we explored the effects of the metabolites of the dopaminergic pathway and other structural analogues of DA on GABAρ1 and the DA gated ion channel (LGC-53) from Caenorhabditis elegans expressed in Xenopus laevis oocytes. Our findings show an antagonistic effect of the metabolite 3-Methoxytyramine (3-MT, IC50 = 285 ± 30 µM) with similar potency compared to DA on induced GABA currents; however, it was inactive on LGC-53. The structural DA analogues and metabolites, 3, 4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 2-phenylethylamine (β-PEA) and 4-amino-1-butanol (4-AM-1-OH), antagonized GABAρ1 currents, whereas β-PEA acted as partial agonists on LGC-53, indicating that the putative binding sites of both receptors may share structural characteristics. These results suggest that the DA metabolites 3-MT, DOPAC and HVA modulate GABAρ1 and possibly affect the activity of the receptors that include this subunit in vivo.

Epigallocatechin Gallate Has a Neurorescue Effect in a Mouse Model of Parkinson Disease

Background: Parkinson disease (PD) is a neurodegenerative disorder that has been associated with many factors, including oxidative stress, inflammation, and iron accumulation. The antioxidant, anti-inflammatory, and iron-chelating properties of epigallocatechin gallate (EGCG), a major polyphenol in green tea, may offer protection against PD.Objective: We sought to determine the neurorescue effects of EGCG and the role of iron in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD.Methods: We evaluated the neurorescue effect of EGCG (25 mg/kg, 7 d, oral administration) against MPTP-induced (20 mg/kg, 3 d, intraperitoneal injection) neurodegeneration in C57 male black mice. Thirty mice weighing ∼25 g were divided into 3 groups: control, MPTP, and MPTP + EGCG. The neurorescue effect of EGCG was assessed with the use of motor behavior tests, neurotransmitter analysis, oxidative stress indicators, and iron-related protein expression.Results: Compared with the control group, MPTP treatment shortened the mice's latency to fall from the rotarod by 16% (P < 0.05), decreased the striatal dopamine concentration by 58% (P < 0.001) and dihydroxyphenylacetic acid by 35% (P < 0.05), and increased serum protein carbonyls by 71% (P = 0.07). However, EGCG rescued MPTP-induced neurotoxicity by increasing the rotational latency by 17% (P < 0.05) to a value similar to the control group. Striatal dopamine concentrations were 40% higher in the MPTP + EGCG group than in the MPTP group (P < 0.05), but the values were significantly lower than in the control group. Compared with the MPTP and control groups, mice in the MPTP + EGCG group had higher substantia nigra ferroportin expression (44% and 35%, respectively) (P < 0.05) but not hepcidin and divalent metal transporter 1 expression.Conclusion: Overall, our study demonstrated that EGCG regulated the iron-export protein ferroportin in substantia nigra, reduced oxidative stress, and exerted a neurorescue effect against MPTP-induced functional and neurochemical deficits in mice.