DA Metabolites Research Articles

Higher exploratory and vigilant behaviors related to higher central dopaminergic activities of Formosan wood mice (Apodemus semotus) in light-dark exploration tests

Formosan wood mice (Apodemus semotus) are endemic rodents in Taiwan. Recently Formosan wood mice exhibit similar locomotor behaviors in the laboratory environment as in the field environment has shown. Contemporaneously, Formosan wood mice have higher moving distances of and central dopaminergic (DAergic) activities than C57BL/6 mice in behavioral test. This study tried to compare the behavioral responses between male Formosan wood mice and male C57BL/6 mice in the light-dark exploration tests. We also measured the levels of DA and 3,4-dihydroxyphenylacetic acid (DOPAC), the primary metabolite of DA, to assess the dopaminergic activity of the medial prefrontal cortex, striatum, and nucleus accumbens. Our data show that Formosan wood mice revealed higher exploration and central DAergic activities than did C57BL/6 mice in the light-dark exploration tests, and diazepam (an anxiolytics) treatment reduced the exploratory activity and central dopaminergic activities in Formosan wood mice, but not in C57BL/6 mice. After repeated exposure to light-dark exploration tests, the latency to dark zone was increased, and the duration in light zone as well as the central DAergic activity were decreased in C57BL/6 mice. This study provides comparative findings; Formosan wood mice showed the higher exploratory activities than C57BL/6 mice did, and their central DAergic activities were related to the behavioral responses in these two mice. This could potentially shed light on the reasons behind the prevalence of higher exploration and central dopaminergic activities. Using Formosan wood mice as a model to study human diseases related to hyperactivity adds significant value to the potential research.

Abstract 17126: Role of Aldehydes, Transient Receptor Potential Ankyrin 1, and Catecholamines in Electronic Cigarette-Induced Endothelial Dysfunction in Mice

Although Electronic Nicotine Delivery Systems (ENDS)-derived aerosols induce endothelial dysfunction (ED), the mechanisms and constituents responsible for ED are unknown. Because ENDS use propylene glycol and vegetable glycerin (PG:VG) that thermally decompose into aldehydes, we hypothesized that acrolein and formaldehyde stimulate ED via the sensory transient receptor potential ankyrin-1 (TRPA1) receptor and the autonomic nervous system (ANS). To test this, female wild-type (WT) and TRPA1-null mice were exposed to either filtered air, PG:VG-derived aerosol, acrolein (AC; 1 ppm), or formaldehyde (FA, 5 ppm). Biomarkers of exposure (AC: 3HPMA; FA: 4TCA) and of harm (aortic ED; urinary catecholamines) were measured. The PG:VG and AC exposures significantly increased urinary 3HPMA levels; and the PG:VG and FA exposures significantly increased urinary 4TCA levels vs air controls. Both PG:VG and FA exposures (6h/d x 4d) in WT mice led to aortic ED (-64.6±3.8; –66.7±5.5 % ACh, respectively) vs air control (-81.5±1.5 % ACh); yet AC exposure did not induce ED (-76±2.9 % ACh). Exposures in TRPA1-null mice to PG:VG, AC, or FA did not lead to ED (-93.0±3.6; –82.8±3.1; -86.6±2.8 % ACh; respectively). As an index of ANS activation and a potential mediator of ED, urinary catecholamines (dopamine, DA; norepinephrine, NE; epinephrine, EPI; serotonin, 5HT) and metabolites were measured by UPLC-MS/MS in early (0-3h) and late (3-18h) post-exposure (PE) samples. In WT mice, PG:VG significantly increased early PE urine levels of NE (and two NE metabolites; +1.5-2.5x), DA metabolite (+1.5x), but not EPI nor 5HT; FA exposure increased DA (+3x), EPI (+2.5x), NE and NE metabolites (+1.2-2.5x), 5HT and 5HT metabolite (+2.5x) only in late PE; while AC exposure decreased early PE DA (-73%) and 5HT (-42%) levels. In TRPA1-null mice, PG:VG and AC exposures increased early PE levels of NE (+2x) and depressed EPI and 5HT levels (-40%); whereas FA exposure increased NE (+2x), EPI (+4x), and 5HT (+1.5) levels in late PE. Aldehydes induce ED through time-dependent mechanisms mediated in part by TRPA1 activation and ANS stimulation. These data indicate that ENDS use may increase cardiovascular disease risk via aldehydes generated by PG:VG independent of nicotine and flavorants.

IPSC‐based modeling of THD recapitulates disease phenotypes and reveals neuronal malformation

Tyrosine hydroxylase deficiency (THD) is a rare genetic disorder leading to dopaminergic depletion and early‐onset Parkinsonism. Affected children present with either a severe form that does not respond to L‐Dopa treatment (THD‐B) or a milder L‐Dopa responsive form (THD‐A). We generated induced pluripotent stem cells (iPSCs) from THD patients that were differentiated into dopaminergic neurons (DAn) and compared with control‐DAn from healthy individuals and gene‐corrected isogenic controls. Consistent with patients, THD iPSC‐DAn displayed lower levels of DA metabolites and reduced TH expression, when compared to controls. Moreover, THD iPSC‐DAn showed abnormal morphology, including reduced total neurite length and neurite arborization defects, which were not evident in DAn differentiated from control‐iPSC. Treatment of THD‐iPSC‐DAn with L‐Dopa rescued the neuronal defects and disease phenotype only in THDA‐DAn. Interestingly, L‐Dopa treatment at the stage of neuronal precursors could prevent the alterations in THDB‐iPSC‐DAn, thus suggesting the existence of a critical developmental window in THD. Our iPSC‐based model recapitulates THD disease phenotypes and response to treatment, representing a promising tool for investigating pathogenic mechanisms, drug screening, and personalized management.

The Effect of Unpredictable Chronic Stress on Rare Minnow (Gobiocypris rarus): Growth, Behaviour and Physiology.

Fishes often adjust their behaviour patterns and physiological responses to cope with changing environments, and different life experiences affect them differently. Fishes might adapt to short-term stress, whereas long-term unpredictable stress may lead to various adverse effects. Although some studies have constructed unpredictable stress models of fish, the effect of unpredictable chronic stress (UCS) in the laboratory is poorly understood in fishes. In the current study, we exposed adult rare minnow to an unpredictable chronic stress protocol over 7 and 14 days and measured their response in terms of growth performance, cortisol, neurotransmitter levels (DA, 5-HT, and related metabolites), and behaviour patterns to comprehensively assess the effects of UCS on laboratory rare minnow. We discovered that specific growth rates were significantly decreased, and cortisol levels were lowered in both 7-days and 14-days stress groups. In the behaviour test, the activity level of the 14-days stress group increased, but there was no significant difference in the number of crossings to the center areas, time spent in the center areas, or the speed. In addition, the levels of DA and 5-HT did not change in the stress groups, but the DOPAC and 5-HIAA levels in the 14 days stress group were significantly higher than those in the control group. These results suggested that UCS influences rare minnow growth performance, behaviour patterns, and cortisol levels, and similar stress should be minimised in the laboratory.

Duodenal Metabolic Profile Changes in Heat-Stressed Broilers

Simple SummaryHeat stress (HS) represents an environmental and socio-economic burden to the poultry industry worldwide. However, the underpinning mechanisms for HS responses are still not well defined. Here, we used a high-throughput analysis to determine the metabolite profiles in acute and chronic heat-stressed broilers in comparison with thermoneutral and pair-fed birds. The results showed that HS altered several duodenal metabolites in a duration-dependent manner and identified potential metabolite signatures.Heat stress (HS) is devastating to poultry production sustainability worldwide. In addition to its adverse effects on growth, welfare, meat quality, and mortality, HS alters the gut integrity, leading to dysbiosis and leaky gut syndrome; however, the underlying mechanisms are not fully defined. Here, we used a high-throughput mass spectrometric metabolomics approach to probe the metabolite profile in the duodenum of modern broilers exposed to acute (AHS, 2 h) or chronic cyclic (CHS, 8 h/day for 2 weeks) HS in comparison with thermoneutral (TN) and pair-fed birds. Ultra high performance liquid chromatography coupled with high resolution mass spectrometry (UHPLC–HRMS) identified a total of 178 known metabolites. The trajectory analysis of the principal component analysis (PCA) score plots (both 2D and 3D maps) showed clear separation between TN and each treated group, indicating a unique duodenal metabolite profile in HS birds. Within the HS groups, partial least squares discriminant analysis (PLS-DA) displayed different clusters when comparing metabolite profiles from AHS and CHS birds, suggesting that the metabolite signatures were also dependent on HS duration. To gain biologically related molecule networks, the above identified duodenal metabolites were mapped into the Ingenuity Pathway Analysis (IPA) knowledge-base and analyzed to outline the most enriched biological functions. Several common and specific top canonical pathways were generated. Specifically, the adenosine nucleotide degradation and dopamine degradation pathways were specific for the AHS group; however, the UDP-D-xylose and UDP-D-glucuronate biosynthesis pathways were generated only for the CHS group. The top diseases enriched by the IPA core analysis for the DA metabolites, including cancer, organismal (GI) injury, hematological, cardiovascular, developmental, hereditary, and neurological disorders, were group-specific. The top altered molecular and cellular functions were amino acid metabolism, molecular transport, small molecule biochemistry, protein synthesis, cell death and survival, and DNA damage and repair. The IPA-causal network predicted that the upstream regulators (carnitine palmitoyltransferase 1B, CPT1B; histone deacetylase 11, HDAC11; carbonic anhydrase 9, CA9; interleukin 37, IL37; glycine N-methyl transferase, GNMT; GATA4) and the downstream mediators (mitogen-activated protein kinases, MAPKs; superoxide dismutase, SOD) were altered in the HS groups. Taken together, these data showed that, independently of feed intake depression, HS induced significant changes in the duodenal metabolite profile in a duration-dependent manner and identified a potential duodenal signature for HS.

Sex-Specific Alterations in Dopamine Metabolism in the Brain after Methamphetamine Self-Administration.

Methamphetamine (METH) use disorder affects both sexes, with sex differences occurring in behavioral, structural, and biochemical consequences. The molecular mechanisms underlying these differences are unclear. Herein, we used a rat model to identify potential sex differences in the effects of METH on brain dopaminergic systems. Rats were trained to self-administer METH for 20 days, and a cue-induced drug-seeking test was performed on withdrawal days 3 and 30. Dopamine and its metabolites were measured in the prefrontal cortex (PFC), nucleus accumbens (NAc), dorsal striatum (dSTR), and hippocampus (HIP). Irrespective of conditions, in comparison to females, male rats showed increased 3,4-dihydroxyphenylalanine (DOPA) in the PFC, dSTR, and HIP; increased cys-dopamine in NAc; and increased 3,4-dihydroxyphenylethanol (DOPET) and 3,4-dihydroxyphenylacetic acid (DOPAC) in dSTR. Males also showed METH-associated decreases in DA levels in the HIP but increases in the NAc. Female rats showed METH-associated decreases in DA, DOPAL, and DOPAC levels in the PFC but increases in DOPET and DOPAC levels in the HIP. Both sexes showed METH-associated decreases in NAc DA metabolites. Together, these data document sex differences in METH SA-induced changes in DA metabolism. These observations provide further support for using sex as an essential variable when discussing therapeutic approaches against METH use disorder in humans.

Oral Administration of L-Citrulline Changes Brain Free Amino Acid and Monoamine Metabolism in Heat-Exposed Broiler Chickens

High ambient temperatures (HT) in summer are becoming more severe due to global warming, leading to severe adverse effects on poultry production. Recently, we have reported that oral administration of L-citrulline (L-Cit) can minimize hyperthermia in chickens under HT. However, whether oral L-Cit can enter the brain, the center for thermoregulation, has not been studied. We investigated the effects of oral administration of L-Cit on free amino acids and monoamines in the diencephalon region of the brain of heat-exposed broilers. Broilers were treated with L-Cit (40 mmol/20 ml/bird), then moved to a chamber at HT (30 ± 1°C) or to a thermoneutral temperature (CT: 22 ± 1°C) chamber for 2 h. Control groups were given methyl cellulose solution and placed in the CT or HT chambers. After 2 h of exposure to HT, there were increased brain concentrations of Cit in comparison with concentrations in broilers exposed to CT, whereas brain ornithine (Orn) concentrations were decreased, and arginine (Arg) concentrations were not changed. Interestingly, oral administration of L-Cit increased brain concentration of Cit, Arg, and Orn under both CT and HT. Tryptophan and its metabolite, serotonin (5-HT) concentrations were lower in the brain under HT than under CT. HT did not change brain concentrations of tyrosine, but dopamine (DA, a metabolite of tyrosine) concentrations decreased, and methoxyhydroxyphenylglycol (MHPG, a metabolite of DA) concentrations increased in comparison with CT. Oral administration of L-Cit decreased brain concentrations of both tryptophan and tyrosine under CT and HT without changing 5-HT; however, DA levels declined under HT. Moreover, MHPG concentrations increased. In conclusion, these results suggest that metabolism of amino acids and metabolism of DA can be enhanced in the brain by oral administration of L-Cit. Metabolic changes in the brain in response to oral administration of L-Cit may influence the thermoregulatory center in the brain, leading to a reduction in body temperature and conferring thermotolerance in heat-exposed broiler chickens.

MicroPET imaging of vesicular monoamine transporter 2 revealed the potentiation of (+)-dihydrotetrabenazine on MPTP-induced degeneration of dopaminergic neurons

IntroductionVesicular monoamine transporter 2 (VMAT2) has been associated with the risk of PD. Genetic reduction of VMAT2 level is reported to increase the vulnerability for dopaminergic neurodegeneration. In this study, by using in vivo microPET imaging with a VMAT2 radioligand [18F]fluoropropyl-(+)-dihydrotetrabenazine ([18F]FP-(+)-DTBZ), we investigated the enhanced role of inhibiting VMAT2 in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced loss of dopaminergic neurons. MethodsThe (+)-α-dihydrotetrabenazine ((+)-DTBZ, an inhibitor of VMAT2, 5 mg/kg), or MPTP (low dose (ld): 10 mg/kg, high dose (hd): 30 mg/kg) or both of them were intraperitoneally injected into C57BL/6 mice for 5 or 10 consecutive days. MicroPET imaging with [18F]FP-(+)-DTBZ was performed to test the dopaminergic neuronal integrity. [18F]FP-(+)-DTBZ uptake in striatum was quantified as standardized uptake value (SUV). The pathological changes in the striata and substantia nigra were confirmed by measuring the DA contents and immunohistochemical staining of tyrosine hydroxylase (TH). ResultsIn vivo imaging results showed that the striatal SUVs of both DTBZ&MPTPld and MPTPhd groups were substantially declined compared to the baseline. Moreover, the striatal uptakes of [18F]FP-(+)-DTBZ in DTBZ&MPTPld and MPTPhd groups were obviously lower than the control, DTBZ group and MPTPld group. Notably, the decrease of the striatal uptake in the DTBZ&MPTPld/10d group was more serious than the DTBZ&MPTPld/5d group and comparable to the MPTPhd group. Consistently, the ratios of DA metabolites to DA in DTBZ&MPTPld/10d and MPTPhd mice were significantly increased. The correlation analysis showed that SUVs were highly correlated to the striatal dopaminergic fiber density and TH-positive dopaminergic neuron number in the substantia nigra. ConclusionsMicroPET brain imaging with [18F]FP-(+)-DTBZ noninvasively revealed that (+)-DTBZ co-administration significantly aggravated the neurotoxicity of MPTP to dopaminergic neurons, suggesting that inhibition of VMAT2 may be related to the pathogenesis of PD and tracing VMAT2 activity with PET imaging is of potential value in monitoring PD progression.

Preclinical Pharmacology of [2-(3-Fluoro-5-Methanesulfonyl-phenoxy)Ethyl](Propyl)amine (IRL790), a Novel Dopamine Transmission Modulator for the Treatment of Motor and Psychiatric Complications in Parkinson Disease.

IRL790 ([2-(3-fluoro-5-methanesulfonylphenoxy)ethyl](propyl)amine, mesdopetam) is a novel compound in development for the clinical management of motor and psychiatric disabilities in Parkinson disease. The discovery of IRL790 was made applying a systems pharmacology approach based on in vivo response profiling. The chemical design idea was to develop a new type of DA D3/D2 receptor type antagonist built on agonist rather than antagonist structural motifs. We hypothesized that such a dopamine antagonist with physicochemical properties similar to agonists would exert antidyskinetic and antipsychotic effects in states of dysregulated dopaminergic signaling while having little negative impact on physiologic dopamine transmission and, hence, minimal liability for side effects related to dopamine-dependent functions. At the level of in vivo pharmacology, IRL790 displays balancing effects on aberrant motor phenotypes, reducing l-DOPA-induced dyskinesias in the rodent 6-hydroxydopamine lesion model and reducing psychostimulant-induced locomotor hyperactivity elicited by pretreatment with either d-amphetamine or dizocilpine, without negatively impacting normal motor performance. Thus, IRL790 has the ability to normalize the behavioral phenotype in hyperdopaminergic as well as hypoglutamatergic states. Neurochemical and immediate early gene (IEG) response profiles suggest modulation of DA neurotransmission, with some features, such as increased DA metabolites and extracellular DA, shared by atypical antipsychotics and others, such as increased frontal cortex IEGs, unique to IRL790. IRL790 also increases extracellular levels of acetylcholine in the prefrontal cortex and ventral hippocampus. At the receptor level, IRL790 appears to act as a preferential DA D3 receptor antagonist. Computational docking studies support preferential affinity at D3 receptors with an agonist-like binding mode. SIGNIFICANCE STATEMENT: This paper reports preclinical pharmacology along with molecular modeling results on IRL790, a novel compound in clinical development for the treatment of motor and psychiatric complications in advanced Parkinson disease. IRL790 is active in models of perturbed dopaminergic and glutamatergic signaling, including rodent 6-hydroxydopamine l-DOPA-induced dyskinesias and psychostimulant-induced hyperactivity, in a dose range that does not impair normal behavior. This effect profile is attributed to interactions at dopamine D2/D3 receptors, with a 6- to 8-fold preference for the D3 subtype.

Roles Played by the Na+/Ca2+ Exchanger and Hypothermia in the Prevention of Ischemia-Induced Carrier-Mediated Efflux of Catecholamines into the Extracellular Space: Implications for Stroke Therapy

The release of [3H]dopamine ([3H]DA) and [3H]noradrenaline ([3H]NA) in acutely perfused rat striatal and cortical slice preparations was measured at 37 °C and 17 °C under ischemic conditions. The ischemia was simulated by the removal of oxygen and glucose from the Krebs solution. At 37 °C, resting release rates in response to ischemia were increased; in contrast, at 17 °C, resting release rates were significantly reduced, or resting release was completely prevented. The removal of extracellular Ca2+ further increased the release rates of [3H]DA and [3H]NA induced by ischemic conditions. This finding indicated that the Na+/Ca2+ exchanger (NCX), working in reverse in the absence of extracellular Ca2+, fails to trigger the influx of Ca2+ in exchange for Na+ and fails to counteract ischemia by further increasing the intracellular Na+ concentration ([Na+]i). KB-R7943, an inhibitor of NCX, significantly reduced the cytoplasmic resting release rate of catecholamines under ischemic conditions and under conditions where Ca2+ was removed. Hypothermia inhibited the excessive release of [3H]DA in response to ischemia, even in the absence of Ca2+. These findings further indicate that the NCX plays an important role in maintaining a high [Na+]i, a condition that may lead to the reversal of monoamine transporter functions; this effect consequently leads to the excessive cytoplasmic tonic release of monoamines and the reversal of the NCX. Using HPLC combined with scintillation spectrometry, hypothermia, which enhances the stimulation-evoked release of DA, was found to inhibit the efflux of toxic DA metabolites, such as 3,4-dihydroxyphenylacetaldehyde (DOPAL). In slices prepared from human cortical brain tissue removed during elective neurosurgery, the uptake and release values for [3H]NA did not differ from those measured at 37 °C in slices that were previously maintained under hypoxic conditions at 8 °C for 20 h. This result indicates that hypothermia preserves the functions of the transport and release mechanisms, even under hypoxic conditions. Oxidative stress (H2O2), a mediator of ischemic brain injury enhanced the striatal resting release of [3H]DA and its toxic metabolites (DOPAL, quinone). The study supports our earlier findings that during ischemia transmitters are released from the cytoplasm. In addition, the major findings of this study that hypothermia of brain slice preparations prevents the extracellular calcium concentration ([Ca2+]o)-independent non-vesicular transmitter release induced by ischemic insults, inhibiting Na+/Cl−-dependent membrane transport of monoamines and their toxic metabolites into the extracellular space, where they can exert toxic effects.

Depressive Symptoms After PCB Exposure: Hypotheses for Underlying Pathomechanisms via the Thyroid and Dopamine System.

Polychlorinated biphenyls’ (PCB) exposure has been reported to be associated with depressive symptoms, which is correlated to lower dopamine- (DA) and thyroxine-concentrations (T4). T4 is necessary for DA-synthesis and it binds to transthyretin (TTR) being transported into the brain. PCBs can displace T4 by binding to TTR itself, being transported into the brain and disturbing DA-synthesis, where depressive symptoms might occur. Consequently, the free T4-concentration (fT4) increases when PCBs bind to TTR. The interaction of PCBs with fT4 and its associations with the main DA metabolite, homovanillic acid (HVA), and depressive symptoms were investigated. In total, 116 participants (91.6% men) were investigated, who took part in three annual examinations (t1–t3) of the HELPcB health surveillance program. Blood was collected for measuring PCBs, hydroxy PCBs (OH-PCBs), and fT4 and urine for HVA. Depressive Symptoms were assessed with a standardized questionnaire. Interactions were tested cross-sectionally with multiple hierarchical regressions and longitudinally with mixed effect models. Related to HVA, an interaction was cross-sectionally found for lower-chlorinated PCBs (LPCBs) and dioxin-like PCBs (dlPCBs); longitudinally only for LPCBs. Related to depressive symptoms, the interaction was found for LPCBs, dlPCBs, and OH-PCBs; longitudinally again only for LPCBs. The results give first hints that a physiological process involving the thyroid and DA system is responsible for depressive symptoms after PCB exposure.

Effects of \u03b1-Synuclein Monomers Administration in the Gigantocellular Reticular Nucleus on Neurotransmission in Mouse Model

The aim of the study was to examine the Braak’s hypothesis to explain the spreading and distribution of the neuropathological changes observed in the course of Parkinson’s disease among ascending neuroanatomical regions. We investigated the neurotransmitter levels (monoamines and amino acid concentration) as well as tyrosine hydroxylase (TH) and transglutaminase-2 (TG2) mRNA expression in the mouse striata (ST) after intracerebral α-synuclein (ASN) administration into gigantocellular reticular nucleus (Gi). Male C57BL/10 Tar mice were used in this study. ASN was administrated by stereotactic injection into Gi area (4 μl; 1 μg/μl) and mice were decapitated after 1, 4 or 12 weeks post injection. The neurotransmitters concentration in ST were evaluated using HPLC detection. TH and TG2 mRNA expression were examined by Real-Time PCR method. At 4 and 12 weeks after ASN administration we observed decrease of DA concentration in ST relative to control groups and we found a significantly higher concentration one of the DA metabolites—DOPAC. At these time points, we also noticed the increase in DA turnover determined as DOPAC/DA ratio. Additionally, at 4 and 12 weeks after ASN injection we noted decreasing of TH mRNA expression. Our findings corresponds with the Braak’s theory about the presence of the first neuropathological changes within brainstem and then with time affecting higher neuroanatomical regions. These results obtained after administration of ASN monomers to the Gi area may be useful to explain the pathogenesis of Parkinson’s disease.

Emotional Roles of Mono-Aminergic Neurotransmitters in Major Depressive Disorder and Anxiety Disorders.

A growing body of researches support a role for dysfunction of serotoninergic, noradrenergic, and dopaminergic systems in the neurobiological processes involved in major depression disorder (MDD) and anxiety disorders (ADs). The physiological changes underlying abnormal signaling of 5-HT, NE, and DA may be due to either reduced presynaptic release of these neurotransmitters or aberrant signal transductions, and thus contributing to the alterations in regulation or function of receptors and/or impaired intracellular signal processing. Animal models demonstrate crucial responsiveness to disturbance of 5-HT, NE, and DA neurotransmissions. Postmortem and biochemical studies have shown altered concentrations of 5-HT, NE, and DA metabolites in brain regions that contribute importantly to regulation of mood and motivation in patients with MDD or ADs. Neuroimaging studies have found abnormal 5-HT, NE, and DA receptors binding and regulation in regard to receptor numbers. Medications that act on 5-HT, NE, and DA neurons or receptors, such as SSRIs and SNRIs, show efficacy in both MDD and ADs. The overlapping treatment response presumably suggests a common mechanism underlying the interaction of these disorders. In this paper, we reviewed studies from multiple disciplines to interpret the role of altered 5-HT, NE and DA mono-amine neurotransmitter functions in both MDD and ADs.

F17464 a new antipsychotic with preferential D3 antagonist, 5-HT1A partial agonist properties. Neurochemical studies

F17464 is a new dopamine receptor antagonist that recently demonstrated antipsychotic activity in a proof of concept study in schizophrenic patients under acute exacerbation. The compound has a unique profile with high affinity for hD3 receptors (Ki = 0.17 nM) and lower affinity for hD2L (Ki = 12.1 nM) and hD2S (Ki = 6.5 nM). F17464 exhibits also high affinity for h5-HT1A receptors (Ki = 0.16 nM). F17464 is a hD3 antagonist (pKB = 9.13), hD2S very week partial agonist (pKB = 7.87, emax 8% of DA stimulated in ERK assay) and a 5-HT1A partial agonist (pEC50 = 7.99). F17464 exhibits consistent affinities for rat striatal D2 (Ki = 4.8 nM) and for rat hippocampal 5-HT1A receptors (Ki = 1.14 nM). Neurochemical studies show that F17464 ip (1 h post-dose) produces a significant dose–dependent increase in the levels of DOPAC and HVA in the frontal cortex, caudate-putamen and limbic forebrain and an increase in 3-MT levels in the latter two regions with no changes in total DA content. The effect is significant at the doses of 0.63–2.5 mg/kg ip (PK/PD data will be provided). This pattern of DA metabolite changes is similar to that described for several antipsychotic drugs in rodents and it is indicative of a cortical effect of F17464. F17464 has a very low cataleptogenic activity in rats and mice and does not induce serotoninergic signs typical of 5-HT1A. F17464 is therefore a novel a D3 preferential antipsychotic with a unique mechanism of action and receptor affinity profile and a consistent effect in neurochemistry studies in rodents.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Psychotomimetic effects of different doses of MK-801 and the underlying mechanisms in a selective memory impairment model

Although N-methyl-d-aspartate receptor antagonists-induced hypoglutamate rodent models are the most well-established models for preclinical studies of schizophrenia-related deficits, they also evoke a wide spectrum of psychotomimetic side effects. It is significant to increase the specificity of hypoglutamate rodent models. In this study, the recognition memory was evaluated in rats by object recognition test (ORT), sensorimotor gating was evaluated by prepulse inhibition of the startle reflex (PPI), and locomotor activity was measured using open field test. High-performance liquid chromatography was used to measure neurotransmitters content in the medial prefrontal cortex (mPFC) and thalamus (THA). Total Akt and phospho-Akt protein was measured by Western blots. Results showed that 0.3mg/kg of MK-801 was most effective in inducing locomotion. 0.3mg/kg of MK-801 was most effective in decreasing PPI. 0.03mg/kg of MK-801 was most effective in decreasing object memory while not affecting exploration manners in the training session. 0.03mg/kg of MK-801 significantly increased HVA and Glu content in the mPFC. 0.1mg/kg of MK-801 significantly decreased GABA content in the THA. 0.03mg/kg of MK-801 significantly decreased Akt phosphorylation in the mPFC, which was related to the ORT index. In conclusion, a dose of 0.03mg/kg MK-801 can establish a “pure” memory impairment model without contaminations of sensorimotor gating and locomotor activity. MK-801-induced cognitive deficits is associated with increased DA metabolites and glutamate content in the mPFC and decreased GABA content in the THA as well as decrease in Akt phosphorylation in the mPFC.

The preferential nNOS inhibitor 7-nitroindazole and the non-selective one NG-nitro-l-arginine methyl ester administered alone or jointly with l-DOPA differentially affect motor behavior and monoamine metabolism in sham-operated and 6-OHDA-lesioned rats

Reciprocal interactions between nitrergic and dopaminergic systems play a key role in the control of motor behavior. In the present study, we performed a comparative analysis of motor behavior (locomotor activity, catalepsy, rotational behavior) and monoamine metabolism in the striatum and substantia nigra of unilaterally sham-operated and 6-OHDA-lesioned rats treated with the preferential neuronal nitric oxide synthase (nNOS) inhibitor 7-nitroindazole (7-NI) or the non-selective one NG-nitro-l-arginine methyl ester (l-NAME), alone or in combination with l-DOPA. Each NOS inhibitor given alone (50mg/kg) induced a distinct catalepsy 30min after injection but only 7-NI impaired spontaneous locomotion after 10min. In 6-OHDA-lesioned rats, chronic l-DOPA (25mg/kg) induced 2.5-h long contralateral rotations. 7-NI (30 and 50mg/kg) markedly reduced the intensity of l-DOPA-induced contralateral rotations while extending their duration until 4.5h whereas l-NAME (50 and 100mg/kg) only tended to attenuate their intensity without affecting the duration. 7-NI but not l-NAME significantly increased endogenous tissue DA levels in the nigrostriatal system of both sham-operated and 6-OHDA-lesioned rats. In l-DOPA-treated group, 7-NI significantly enhanced the l-DOPA-derived tissue DA content in this system and decreased the level of the intracellular DA metabolite DOPAC produced by monoamine oxidase (MAO). In contrast to 7-NI, l-NAME decreased markedly DA content and did not affect DOPAC level in the ipsilateral striatum. It means that the differences in 7-NI and l-NAME-mediated modulation of l-DOPA-induced behavioral and biochemical effects resulted not only from the inhibition of NOS activity but also from differences in their ability to inhibit MAO.

Dietary supplementation with resveratrol protects against striatal dopaminergic deficits produced by in utero LPS exposure

The purpose of this study was to determine the effect of dietary supplementation with the anti-inflammatory compound resveratrol in pregnant dams on lipopolysaccharide (LPS)-induced dopaminergic deficits in pups exposed to LPS in utero. Gravid female rats were fed with a resveratrol-enriched diet during gestational days 3–22.5 (E3–E22.5) and received an intraperitoneal (i.p.) injection of 1mg/kg LPS at E10.5. The striata were isolated from the pups at postnatal days 10 (P10) and P21. LPS-induced dopaminergic deficits were noted at P21, but not P10. These DA deficits at P21 were exhibited by a loss of DA and DA metabolite [3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA)] levels and tyrosine hydroxylase (TH) expression in the striatum. The LPS-induced loss of DA, DA metabolites, and TH expression were attenuated in the striata of pups from the dams fed with the resveratrol-supplemented diet. These data suggest that a resveratrol-supplemented diet may restore homeostasis of the striatal DA neuronal system following disruption by LPS.

Evidence for impaired function of dopaminergic system in Wfs1-deficient mice

Immunohistological studies suggest abundant expression of Wfs1 protein in neurons and nerve fibers that lie in the vicinity of dopaminergic (DA-ergic) fibers and neurons. Therefore, we sought to characterize the function of DA-ergic system in Wfs1-deficient mice. In wild-type mice, amphetamine, an indirect agonist of DA, caused significant hyperlocomotion and increase in tissue DA levels in the dorsal and ventral striatum. Both effects of amphetamine were significantly blunted in homozygous Wfs1-deficient mice. Motor stimulation caused by apomorphine, a direct DA receptor agonist, was somewhat stronger in Wfs1-deficient mice compared to their wild-type littermates. However, apomorphine caused a similar reduction in levels of DA metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid) in the dorsal and ventral striatum in all genotypes. Behavioral sensitization to repeated treatment with amphetamine (2.5mg/kg) was observed in wild-type, but not in Wfs1-deficient mice. The expression of DA transporter gene (Dat) mRNA was significantly lower in the midbrain of male and female homozygous mice compared to wild-type littermates. Altogether, the blunted effects of amphetamine and the reduced gene expression of DA transporter are probably indicative of an impaired functioning of the DA-ergic system in Wfs1-deficient mice.

Neurochemical changes in animal models of Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative syndrome associated with selective loss of dopaminergic neurons in the striatum. It is believed that both mitochondrial dysfunction and oxidative stress (OS) play important role in the pathogenesis of PD. Development of an effective causal therapy should be focused on preventing or at least retarding the neurodegenerative process underlying the disease. In chronic in fusion PD model studied the effect of rotenone on the content, and release of striatal neurotransmitters of rat upon OS by H2O 2 perfusion. The effects of anti-Parkinsonian drugs were examined in vitro rotenone PD, OS slices model. The role of P2X7 receptor (P2X7r) formed by 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) or in vitro rotenone treatment using C57/BI6 and P2X7r knockout mice. Neurochemical response was determined using microvolume perfusion method, HPLC separation of dansylated samples. Dopamine o-quinone (DAQ) oxidized metabolite of DA was detected electrochemically at -100 mV potential in reduction working mode. The dopamine content in the rat striatum is decreased in response to chronic intravenous rotenone infusion. However, surviving dopaminergic neurons take up and release only a slightly lower amount of DA in response to electrical stimulation. Striatal dopaminergic neurons showed increased susceptibility to OS, responding with enhanced release of DA and with formation of toxic metabolite DAQ. The loss of DA and ATP and formation of DAQ induced by OS confirmed the impairment of striatum upon in vitro rotenone. Formation of DAQ at the end effect of OS confirmed the impairment of dopaminergic function by rotenone. However, when applied rotenone with l-DOPA treatment the endogenous DAQ was detected in perfusion samples. However, when applied rotenone with l-DOPA treatment the endogenous DAQ was detected in the micro-volume perfusion samples. Conversely, when rasagiline and trolox were in use these DA-quinones metabolites were not detectable. Rotenone treatment elicited a similar reduction in ATP content in the substantia nigra of both genotypes, whereas reduction of ATP was more pronounced after rotenone treatment in striatal slices of P2X7 deficient mice. Although the level of the endocannabinoid, 2-AG, was elevated by rotenone in the striatum of wild-type mice, an effect that was absent in mice deficient in P2X7 receptors. Genetic deletion of P2X7 receptors did not change depletion of striatal endogenous DA content after in vivo MPTP or in vitro rotenone treatment. Although the endogenous amino acids content and the level of the endocannabinoid, AEA was elevated by MPTP in the striatum of mice, but 2-AG remained unchanged in mice deficient in P2X7 receptors. In conclusion, oxidative stress induced, pathological DA release and the formation of toxic metabolites of DA are distinctly modified by the tested antiparkinsonian drugs and P2X7 receptor deficiency does not promote the survival of dopaminergic neurons.

Effects of perinatal exposure to low dose of bisphenol A on anxiety like behavior and dopamine metabolites in brain

Bisphenol A (BPA), an endocrine-disrupting chemical, is widely present in the environment. It has been reported that perinatal exposure to low doses of BPA that are less than the tolerable daily intake level (50μg/kg/day) affects anxiety-like behavior and dopamine levels in the brain. Although the dopaminergic system in the brain is considered to be related to anxiety, no study has reported the effects of low-dose BPA exposure on the dopaminergic system in the brain and on anxiety-like behavior using the same methods of BPA exposure. To investigate the relationship between alterations in anxiety-like behavior and changes in the dopaminergic system in the brain induced by BPA, we examined the effects of BPA on anxiety-like behavior using an open field test in juvenile and adult mice and measured DA and DOPAC levels and the DOPAC/DA ratio in the dorsal hippocampus (HIP), amygdala (AMY), and medulla oblongata (MED) using high-performance liquid chromatography (HPLC) in adult mice. In males, BPA decreased the time spent in the center area of the open field in both juveniles and adults. In addition, BPA increased DA levels in the dorsal HIP and MED and decreased the DOPAC/DA ratio in the dorsal HIP, AMY, and MED in adults. The activity of monoamine oxidase (MAO)-B, the enzyme that metabolizes DA into DOPAC, was reduced in the MED. In females, those changes were not observed. These results suggest that an increase in anxiety-like behavior induced by perinatal exposure to BPA may be related to decreases in DA metabolites in the brain, and there are sex differences in those BPA effects.