Postsynaptic nigrostriatal dopamine receptors and their role in movement regulation

Neural underpinnings of fine motor skills under stress and anxiety: A review

This review offers a comprehensive examination of how stress and anxiety affect motor behavior, particularly focusing on fine motor skills and gait adaptability. We explore the role of several neurochemicals, including brain-derived neurotrophic factor (BDNF) and dopamine, in modulating neural plasticity and motor control under these affective states. The review highlights the importance of developing therapeutic strategies that enhance motor performance by leveraging the interactions between key neurochemicals. Additionally, we investigate the complex interplay between emotional-cognitive states and sensorimotor behaviors, showing how stress and anxiety disrupt neural integration, leading to impairments in skilled movements and negatively impacting quality of life. Synthesizing evidence from human and rodent studies, we provide a detailed understanding of the relationships among stress, anxiety, and motor behavior. Our findings reveal neurophysiological pathways, behavioral outcomes, and potential therapeutic targets, emphasizing the intricate connections between neurobiological mechanisms, environmental factors, and motor performance.

Dopamine Pharmacodynamics: New Insights

Dopamine is a key neurotransmitter involved in physiological processes such as motor control, motivation, reward, cognitive function, and maternal and reproductive behaviors. Therefore, dysfunctions of the dopaminergic system are related to a plethora of human diseases. Dopamine, via different circuitries implicated in compulsive behavior, reward, and habit formation, also represents a key player in substance use disorder and the formation and perpetuation of mechanisms leading to addiction. Here, we propose dopamine as a model not only of neurotransmission but also of neuromodulation capable of modifying neuronal architecture. Abuse of substances like methamphetamine, cocaine, and alcohol and their consumption over time can induce changes in neuronal activities. These modifications lead to synaptic plasticity and finally to morphological and functional changes, starting from maladaptive neuro-modulation and ending in neurodegeneration.

Drug repurposing of dopaminergic drugs to inhibit ataxin-3 aggregation

The accumulation of mutant ataxin-3 (Atx3) in neuronal nuclear inclusions is a pathological hallmark of Machado-Joseph disease (MJD), also known as Spinocerebellar Ataxia Type 3. Decreasing the protein aggregation burden is a possible disease-modifying strategy to tackle MJD and other neurodegenerative disorders for which only symptomatic treatments are currently available. We performed a drug repurposing screening to identify inhibitors of Atx3 aggregation with known toxicological and pharmacokinetic profiles. Interestingly, dopamine hydrochloride and other catecholamines are among the most potent inhibitors of Atx3 aggregation in vitro. Our results indicate that low micromolar concentrations of dopamine markedly delay the formation of mature amyloid fibrils of mutant Atx3 through the inhibition of the earlier oligomerization steps. Although dopamine itself does not cross the blood-brain barrier, dopamine levels in the brain can be increased by low doses of dopamine precursors and dopamine agonists commonly used to treat Parkinsonian symptoms. In agreement, treatment with levodopa ameliorated motor symptoms in a C. elegans model of MJD. These findings suggest a possible application of dopaminergic drugs to halt or reduce Atx3 accumulation in the brains of MJD patients.

Gut Microbiome Dysbiosis as a Potential Risk Factor for Idiopathic Toe-Walking in Children: A Review

Idiopathic toe walking (ITW) occurs in about 5% of children. Orthopedic treatment of ITW is complicated by the lack of a known etiology. Only half of the conservative and surgical methods of treatment give a stable positive result of normalizing gait. Available data indicate that the disease is heterogeneous and multifactorial. Recently, some children with ITW have been found to have genetic variants of mutations that can lead to the development of toe walking. At the same time, some children show sensorimotor impairment, but these studies are very limited. Sensorimotor dysfunction could potentially arise from an imbalanced production of neurotransmitters that play a crucial role in motor control. Using the data obtained in the studies of several pathologies manifested by the association of sensory-motor dysfunction and intestinal dysbiosis, we attempt to substantiate the notion that malfunction of neurotransmitter production is caused by the imbalance of gut microbiota metabolites as a result of dysbiosis. This review delves into the exciting possibility of a connection between variations in the microbiome and ITW. The purpose of this review is to establish a strong theoretical foundation and highlight the benefits of further exploring the possible connection between alterations in the microbiome and TW for further studies of ITW etiology.

Perinatal exposure to paracetamol: Dose and sex-dependent effects in behaviour and brain's oxidative stress markers in progeny

Paracetamol (PAR) has been employed worldwide for pain and fever treatment during pregnancy and lactation. Epidemiologic studies have shown that exposure to PAR can increase the risk for developmental disorders, such as attention-deficit hyperactive disorder and autism spectrum disorder. This study aimed to investigate if gestational and lactational exposure to human-relevant doses of PAR could alter behavioural and brain oxidative stress parameters in the rat`s offspring. Wistar dams were gavaged daily with water or PAR (35 mg/kg/ or 350 mg/kg) during gestational day 6 to weaning (postnatal day 21). Behavioural assessments occurred at post-natal days 10 (nest seeking test), 27 (behavioural stereotypy) and 28 (three chamber sociability test and open field). Concentration of advanced oxidation protein products (AOPP), reduced glutathione (GSH), lipid hydroperoxides (LOOH) and activity of superoxide dismutase (SOD) were estimate in prefrontal cortex, hippocampus, striatum and cerebellum of 22-day-old rats. Compared to CON animals, males exposed to PAR during pregnancy and lactation augmented apomorphine-induced stereotyped behaviour (350 mg/kg) and ambulation in open-field test (35 mg/kg). Reduced exploratory behaviour in three chamber sociability test was observed in pups exposed to PAR at 350 mg/kg in both sexes. PAR treatment decreased hippocampal GSH level and striatal SOD activity in males exposed to 35 mg/kg, suggesting the vulnerability of these areas in PAR-induced developmental neurotoxicity. Findings suggest PAR use during pregnancy and lactation as a potential risk factor for neurodevelopmental disorders with males being more susceptible.

A Gain-of-Function Variant in Dopamine D2 Receptor and Progressive Chorea and Dystonia Phenotype

BACKGROUND

We describe a 4-generation Dutch pedigree with a unique dominantly inherited clinical phenotype of a combined progressive chorea and cervical dystonia carrying a novel heterozygous dopamine D2 receptor (DRD2) variant.

OBJECTIVES

The objective of this study was to identify the genetic cause of the disease and to further investigate the functional consequences of the genetic variant.

METHODS

After detailed clinical and neurological examination, whole-exome sequencing was performed. Because a novel variant in the DRD2 gene was found as the likely causative gene defect in our pedigree, we sequenced the DRD2 gene in a cohort of 121 Huntington-like cases with unknown genetic cause (Germany). Moreover, functional characterization of the DRD2 variant included arrestin recruitment, G protein activation, and G protein-mediated inhibition of adenylyl cyclase determined in a cell model, and G protein-regulated inward-rectifying potassium channels measured in midbrain slices of mice.

RESULT

We identified a novel heterozygous variant c.634A > T, p.Ile212Phe in exon 5 of DRD2 that cosegregated with the clinical phenotype. Screening of the German cohort did not reveal additional putative disease-causing variants. We demonstrated that the D2S/L -I212 F receptor exhibited increased agonist potency and constitutive activation of G proteins in human embryonic kidney 239 cells as well as significantly reduced arrestin3 recruitment. We further showed that the D2S -I212 F receptor exhibited aberrant receptor function in mouse midbrain slices.

CONCLUSIONS

Our results support an association between the novel p.Ile212Phe variant in DRD2, its modified D2 receptor activity, and the hyperkinetic movement disorder reported in the 4-generation pedigree. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Social isolation is closely linked to a marked reduction in physical activity in male mice

The effects of social isolation on an individual's behavior is an important field of research, especially as public health officials encourage social distancing to prevent the spread of pandemic disease. In this study we evaluate the effects of social isolation on physical activity in mice. Utilizing a pixel-based tracking system, we continuously monitored the movement of isolated mice compared with paired cage mates in the home cage environment. We demonstrate that mice that are socially isolated dramatically decrease their movement when separated from their cage mate, and especially in the dark cycle, when mice are normally most active. When isolated mice are re-paired with their original cage mate, this effect is reversed, and mice return to their prior levels of activity. These findings suggest a close link between social isolation and physical activity, and are of particular interest in the wake of coronavirus disease 2019, when many are forced into isolation. Social isolation may affect an individual's overall activity levels in humans too, which may have unintended effects on health that deserve further consideration.

Spaceflight and brain plasticity: Spaceflight effects on regional expression of neurotransmitter systems and neurotrophic factors encoding genes

The critical problem of space exploration is the effect of long-term space travel on brain functioning. Current information concerning the effects of actual spaceflight on the brain was obtained on rats and mice flown on five missions of Soviet/Russian biosatellites, NASA Neurolab Mission STS90, and International Space Station (ISS). The review provides converging lines of evidence that: 1) long-term spaceflight affects both principle regulators of brain neuroplasticity - neurotransmitters (5-HT and DA) and neurotrophic factors (CDNF, GDNF but not BDNF); 2) 5-HT- (5-HT_2A receptor and MAO A) and especially DA-related genes (TH, MAO A, COMT, D1 receptor, CDNF and GDNF) belong to the risk neurogenes; 3) brain response to spaceflight is region-specific. Substantia nigra, striatum and hypothalamus are highly sensitive to the long-term spaceflight: in these brain areas spaceflight decreased the expression of both DA-related and neurotrophic factors genes. Since DA system is involved in the regulation of movement and cognition the data discussed in the review could explain dysfunction of locomotion and behavior of astronauts and direct further investigations to the DA system.

Dnmt3a2/Dnmt3L Overexpression in the Dopaminergic System of Mice Increases Exercise Behavior through Signaling Changes in the Hypothalamus

Dnmt3a2, a de novo DNA methyltransferase, is induced by neuronal activity and participates in long-term memory formation with the increased expression of synaptic plasticity genes. We wanted to determine if Dnmt3a2 with its partner Dnmt3L may influence motor behavior via the dopaminergic system. To this end, we generated a mouse line, Dnmt3a2/3L^Dat/wt, with dopamine transporter (DAT) promotor driven Dnmt3a2/3L overexpression. The mice were studied with behavioral paradigms (e.g., cylinder test, open field, and treadmill), brain slice patch clamp recordings, ex vivo metabolite analysis, and in vivo positron emission tomography (PET) using the dopaminergic tracer 6-[¹⁸F]FMT. The results showed that spontaneous activity and exercise performance were enhanced in Dnmt3a2/3L^Dat/wt mice compared to Dnmt3a2/3L^wt/wt controls. Dopaminergic substantia nigra pars compacta neurons of Dnmt3a2/3L^Dat/wt animals displayed a higher fire frequency and excitability. However, dopamine concentration was not increased in the striatum, and dopamine metabolite concentration was even significantly decreased. Striatal 6-[¹⁸F]FMT uptake, reflecting aromatic L-amino acid decarboxylase activity, was the same in Dnmt3a2/3L^Dat/wt mice and controls. [¹⁸F]FDG PET showed that hypothalamic metabolic activity was tightly linked to motor behavior in Dnmt3a2/3L^Dat/wt mice. Furthermore, dopamine biosynthesis and motor-related metabolic activity were correlated in the hypothalamus. Our findings suggest that Dnmt3a2/3L, when overexpressed in dopaminergic neurons, modulates motor performance via activation of the nigrostriatal pathway. This does not involve increased dopamine synthesis.

Aberrant Dopamine Receptor Signaling Plays Critical Role in the Impairment of Striatal Neurons in Experimental Cerebral Malaria

One-fourth survivors of cerebral malaria (CM) retain long-term cognitive and behavioral deficits. Structural abnormalities in striatum are reported in 80% of children with CM. Dopamine receptors (D1 and D2) are widely expressed in striatal medium spiny neurons (MSNs) that regulate critical physiological functions related to behavior and cognition. Dysregulation of dopamine receptors alters the expression of downstream proteins such as dopamine- and cAMP-regulated phosphoprotein (DARPP), Ca²⁺/calmodulin-dependent protein kinase II alpha (CaMKIIα), and p25/cyclin-dependent kinase 5 (cdk5). However, the role of dopamine receptor signaling dysfunction on the outcome of striatal neuron degeneration is unknown underlying the pathophysiology of CM. Using experimental CM (ECM), the present study attempted to understand the role of aberrant dopamine receptor signaling and its possible relation in causing MSNs morphological impairment. The effect of antimalarial drug artemether (ARM) rescue therapy was also assessed after ECM on the outcome of dopamine receptors downstream signaling. ECM was induced in C57BL/6 mice (male and female) infecting with Plasmodium berghei ANKA (PbA) parasite that reiterates the clinical setting of CM. We demonstrated that ECM caused a significant increase in the expression of D1, D2 receptors, phosphorylated DARPP, p25, cdk5, CaMKIIα, and D1-D2 heteromers. A substantial increase in neuronal damage observed in the dorsolateral striatum region of ECM brains (particularly in MSNs) as revealed by increased Fluoro-Jade C staining, reduced dendritic spine density, and impaired dendritic arborization with varicosities. While the ARM rescue therapy significantly altered the effects of ECM induced dopamine receptor signaling dysfunction and neurodegeneration. Overall, our data suggest that dysregulation of dopamine receptor signaling plays an important role in the degeneration of MSNs, and the ARM rescue therapy might provide better insights to develop effective therapeutic strategies for CM.

Attractiveness and neural processing of infant faces: effects of a facial abnormality but not dopamine

Adults' caregiving responses toward infants may have important origins in the perception and processing of infant cues as well as the motivation to attend to these cues. Moreover, some biological processes, such as dopaminergic neurotransmission, may be crucially involved. Although infant stimuli are generally experienced as cute and rewarding, infants with a visible disability may be regarded much less favorably than others, perhaps dependent on differences in perception, motivation, and neural processing. The current study investigated effects of administered dopamine on the perceived attractiveness and neurophysiological indices of attention and processing (i.e., the P1, P2, and N170 components of the event-related potential) of infant faces with and without a cleft lip. No evidence for effects of dopamine was found, but we replicated the finding that the decreased attractiveness of infants with a cleft lip was mediated by decreased configural face processing (smaller N170 amplitudes), but not more general attentional and/or executive processing (P2). The current findings show once again the unfavorable consequences of a cleft lip, but also highlight the importance of combining and relating measures across various levels of analysis and underscore the importance of replication.

Auraptene Mitigates Parkinson's Disease-Like Behavior by Protecting Inhibition of Mitochondrial Respiration and Scavenging Reactive Oxygen Species

Current therapeutics for Parkinson’s disease (PD) are only effective in providing relief of symptoms such as rigidity, tremors and bradykinesia, and do not exert disease-modifying effects by directly modulating mitochondrial function. Here, we investigated auraptene (AUR) as a potent therapeutic reagent that specifically protects neurotoxin-induced reduction of mitochondrial respiration and inhibits reactive oxygen species (ROS) generation. Further, we explored the mechanism and potency of AUR in protecting dopaminergic neurons. Treatment with AUR significantly increased the viability of substantia nigra (SN)-derived SN4741 embryonic dopaminergic neuronal cells and reduced rotenone-induced mitochondrial ROS production. By inducing antioxidant enzymes AUR treatment also increased oxygen consumption rate. These results indicate that AUR exerts a protective effect against rotenone-induced mitochondrial oxidative damage. We further assessed AUR effects in vivo, investigating tyrosine hydroxylase (TH) expression in the striatum and substantia nigra of MPTP-induced PD model mice and behavioral changes after injection of AUR. AUR treatment improved movement, consistent with the observed increase in the number of dopaminergic neurons in the substantia nigra. These results demonstrate that AUR targets dual pathogenic mechanisms, enhancing mitochondrial respiration and attenuating ROS production, suggesting that the preventative potential of this natural compound could lead to improvement in PD-related neurobiological changes.

Dopamine Release Dynamics in the Tuberoinfundibular Dopamine System

The relationship between neuronal impulse activity and neurotransmitter release remains elusive. This issue is especially poorly understood in the neuroendocrine system, with its particular demands on periodically voluminous release of neurohormones at the interface of axon terminals and vasculature. A shortage of techniques with sufficient temporal resolution has hindered real-time monitoring of the secretion of the peptides that dominate among the neurohormones. The lactotropic axis provides an important exception in neurochemical identity, however, as pituitary prolactin secretion is primarily under monoaminergic control, via tuberoinfundibular dopamine (TIDA) neurons projecting to the median eminence (ME). Here, we combined electrical or optogenetic stimulation and fast-scan cyclic voltammetry to address dopamine release dynamics in the male mouse TIDA system. Imposing different discharge frequencies during brief (3 s) stimulation of TIDA terminals in the ME revealed that dopamine output is maximal at 10 Hz, which was found to parallel the TIDA neuron action potential frequency distribution during phasic discharge. Over more sustained stimulation periods (150 s), maximal output occurred at 5 Hz, similar to the average action potential firing frequency of tonically active TIDA neurons. Application of the dopamine transporter blocker, methylphenidate, significantly increased dopamine levels in the ME, supporting a functional role of the transporter at the neurons' terminals. Lastly, TIDA neuron stimulation at the cell body yielded perisomatic release of dopamine, which may contribute to an ultrafast negative feedback mechanism to constrain TIDA electrical activity. Together, these data shed light on how spiking patterns in the neuroendocrine system translate to vesicular release toward the pituitary and identify how dopamine dynamics are controlled in the TIDA system at different cellular compartments.SIGNIFICANCE STATEMENT A central question in neuroscience is the complex relationship between neuronal discharge activity and transmitter release. By combining optogenetic stimulation and voltammetry, we address this issue in dopamine neurons of the neuroendocrine system, which faces particular spatiotemporal demands on exocytotic release; large amounts of neurohormone need to be secreted into the portal capillaries with precise timing to adapt to physiological requirements. Our data show that release is maximal around the neurons' default firing frequency. We further provide support for functional dopamine transport at the neurovascular terminals, shedding light on a long-standing controversy about the existence of neuroendocrine transmitter reuptake. Finally, we show that dopamine release occurs also at the somatodendritic level, providing a substrate for an ultrashort autoregulatory feedback loop.

Current Understanding of the Role of Neuronal Calcium Sensor 1 in Neurological Disorders

Neuronal calcium sensor 1 (NCS-1) is a high-affinity calcium-binding protein and its ubiquitous expression in the nervous system implies a wide range of functions. To date, it has been implicated in regulation of calcium channels in both axonal growth cones and presynaptic terminals, pre- and postsynaptic plasticity mechanisms, learning and memory behaviors, dopaminergic signaling, and axonal regeneration. This review summarizes these functions and relates them to several diseases in which NCS-1 plays a role, such as schizophrenia and bipolar disorder, X-linked mental retardation and fragile X syndrome, and spinal cord injury. Many questions remain unanswered about the role of NCS-1 in these diseases, particularly as the genetic factors that control NCS-1 expression in both normal and diseased states are still poorly understood. The review further identifies the therapeutic potential of manipulating the interaction of NCS-1 with its many targets and suggests directions for future research on the role of NCS-1 in these disorders.

Changes in Dopamine Signalling Do Not Underlie Aberrant Hippocampal Plasticity in a Mouse Model of Huntington's Disease

Altered dopamine receptor labelling has been demonstrated in presymptomatic and symptomatic Huntington's disease (HD) gene carriers, indicating that alterations in dopaminergic signalling are an early event in HD. We have previously described early alterations in synaptic transmission and plasticity in both the cortex and hippocampus of the R6/1 mouse model of Huntington's disease. Deficits in cortical synaptic plasticity were associated with altered dopaminergic signalling and could be reversed by D1- or D2-like dopamine receptor activation. In light of these findings we here investigated whether defects in dopamine signalling could also contribute to the marked alteration in hippocampal synaptic function. To this end we performed dopamine receptor labelling and pharmacology in the R6/1 hippocampus and report a marked, age-dependent elevation of hippocampal D1 and D2 receptor labelling in R6/1 hippocampal subfields. Yet, pharmacological inhibition or activation of D1- or D2-like receptors did not modify the aberrant synaptic plasticity observed in R6/1 mice. These findings demonstrate that global perturbations to dopamine receptor expression do occur in HD transgenic mice, similarly in HD gene carriers and patients. However, the direction of change and the lack of effect of dopaminergic pharmacological agents on synaptic function demonstrate that the perturbations are heterogeneous and region-specific, a finding that may explain the mixed results of dopamine therapy in HD.

Genotype-Dependent Difference in 5-HT2C Receptor-Induced Hypolocomotion: Comparison with 5-HT2A Receptor Functional Activity

In the present study behavioral effects of the 5-HT2C serotonin receptor were investigated in different mouse strains. The 5-HT2C receptor agonist MK-212 applied intraperitoneally induced significant dose-dependent reduction of distance traveled in the open field test in CBA/Lac mice. This effect was receptor-specific because it was inhibited by the 5-HT2C receptor antagonist RS102221. To study the role of genotype in 5-HT2C receptor-induced hypolocomotion, locomotor activity of seven inbred mouse strains was measured after MK-212 acute treatment. We found that the 5-HT2C receptor stimulation by MK-212 decreased distance traveled in the open field test in CBA/Lac, C57Bl/6, C3H/He, and ICR mice, whereas it failed to affect locomotor activity in DBA/2J, Asn, and Balb/c mice. We also compared the interstrain differences in functional response to 5-HT2C and 5-HT2A receptors activation measured by the quantification of receptor-mediated head-twitches. These experiments revealed significant positive correlation between 5-HT2C and 5-HT2A receptors functional responses for all investigated mouse strains. Moreover, we found that 5-HT2A receptor activation with DOI did not change locomotor activity in CBA/Lac mice. Taken together, our data indicate the implication of 5-HT2C receptors in regulation of locomotor activity and suggest the shared mechanism for functional responses mediated by 5-HT2C and 5-HT2A receptors.

Interferência do tratamento medicamentoso imediato e tardio na doença de Parkinson no gerenciamento da disfagia

A Doença de Parkinson apresenta grande incidência na população idosa, gerando comprometimento motor progressivo, que afeta várias funções, dentre as quais se destaca a deglutição. Esse trabalho teve como objetivo relacionar a disfagia na Doença de Parkinson aos efeitos imediatos e/ou tardios do tratamento medicamentoso, que de forma direta ou indireta interferirá no gerenciamento fonoaudiológico. Fizemos uma revisão de literatura nas bases de dados eletrônicas Lilacs, Scielo, Medline e Pubmed no período de 2001 a 2011, utilizando os termos livres “Doença de Parkinson”; (Parkinson Disease), “deglutição”; (deglutition), “disfagia”; (dysphagia), “preparações farmacêuticas”; (pharmaceutical preparations), “levodopa”;, “videofluoroscopia”; (videofluoroscopy), além de um documento governamental (OPAS, 2002), artigos relevantes e exemplares da literatura americana e brasileira sobre o tema. A literatura aponta a Levodopa como o principal tratamento farmacológico da doença de Parkinson. Contudo, a melhora dos sintomas motores deve ser ponderada em função da ocorrência de efeitos colaterais importantes, sejam imediatos ou tardios. Até o momento não há respostas consistentes a favor da melhora da disfagia como resultado do tratamento farmacológico, cujos efeitos podem interferir direta ou indiretamente sobre as manifestações disfágicas e de várias formas. Assim, torna-se fundamental o registro das medicações como parte da anamnese, considerando que tais dados possam auxiliar na orientação/reorientação da conduta fonoaudiológica, especialmente em contexto interdisciplinar. A despeito da possibilidade do doente de Parkinson responder de forma inconsistente à terapia farmacológica, vale ressaltar que o profissional deve estar atento à presença de efeitos colaterais como fatores modificadores do quadro de disfagia orofaríngea na Doença de Parkinson idiopática.

Molecular characterization, expression profile, and polymorphism of goose dopamine D1 receptor gene

Dopamine D1 receptor (DRD1) is one of the dopamine receptors with seven transmembrane domains that are coupled to the G protein. In the present study, we cloned the full coding region of DRD1 gene by the reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends from the goose hypothalamus tissues. Results showed that the goose DRD1 cDNA (GenBank: KF156790) contained a 1,356 bp open reading frame encoding a protein 452 amino acid with a molecular weight of 50.52 kDa and a isoelectric point of 6.96. Bioinformatics analysis indicated that the deduced amino acid sequence was 71-98% identical to the DRD1 protein of other species, contained seven transmembrane domains and four N-glycosylation sites. A phylogenetic tree analysis revealed that the deduced goose DRD1 protein had a close genetic relationship and evolutional distance with that of duck, chicken, and zebra finch. The semi-quantitative RT-PCR analysis displayed goose DRD1 gene was widely expressed in all detected tissues, including heart, lung, liver, spleen, kidney, breast muscle, duodenum, sebum, pituitary, hypothalamus, ovary and oviduct. Eighteen single nucleotide polymorphisms were indentified in 3,169 bp length of this gene. For G90A mutation, the genotyping analysis of PCR-TspRI-RFLP showed the allele G was in dominance in all detected goose breeds, and the allele frequencies of this polymorphism were significantly different between Chinese goose breeds and foreign breeds (P<0.01). These findings will help us understand the functions of the DRD1 gene and the molecular breeding in geese.

Overexpression of Adenosine A2A Receptors in Rats: Effects on Depression, Locomotion, and Anxiety

Adenosine A2A receptors (A2AR) are a sub-type of receptors enriched in basal ganglia, activated by the neuromodulator adenosine, which interact with dopamine D2 receptors. Although this reciprocal antagonistic interaction is well-established in motor function, the outcome in dopamine-related behaviors remains uncertain, in particular in depression and anxiety. We have demonstrated an upsurge of A2AR associated to aging and chronic stress. Furthermore, Alzheimer's disease patients present A2AR accumulation in cortical areas together with depressive signs. We now tested the impact of overexpressing A2AR in forebrain neurons on dopamine-related behavior, namely depression. Adult male rats overexpressing human A2AR under the control of CaMKII promoter [Tg(CaMKII-hA2AR)] and aged-matched wild-types (WT) of the same strain (Sprague-Dawley) were studied. The forced swimming test (FST), sucrose preference test (SPT), and the open-field test (OFT) were performed to evaluate behavioral despair, anhedonia, locomotion, and anxiety. Tg(CaMKII-hA2AR) animals spent more time floating and less time swimming in the FST and presented a decreased sucrose preference at 48 h in the SPT. They also covered higher distances in the OFT and spent more time in the central zone than the WT. The results indicate that Tg(CaMKII-hA2AR) rats exhibit depressive-like behavior, hyperlocomotion, and altered exploratory behavior. This A2AR overexpression may explain the depressive signs found in aging, chronic stress, and Alzheimer's disease.

Molecular characterization and differential expression of multiple goose dopamine D2 receptors

Dopamine D2 receptor (DRD2) gene, a member of the dopamine receptors gene family, has been studied as a candidate gene for broodiness due to its special effects on avian prolactin secretion. Here, the genomic DNA and cDNA sequences of goose (Anser cygnoides) DRD2 gene were cloned and characterized for the first time. The goose DRD2 cDNA is 1353bp in length and encodes a protein of 450 amino acids. The length of goose DRD2 genomic DNA is 8350bp, including seven exons and six introns. We identified four goose DRD2 variants, which were generated due to alternative splicing. Bioinformatics analysis indicates that all the deduced DRD2 amino acid sequences contain seven putative transmembrane domains and four potential N-glycosylation sites. A phylogenetic tree based on amino acid sequences displays that the goose DRD2 protein is closely related to those of avian species. Semi-quantitative RT-PCR analysis demonstrates that the DRD2-1, DRD2-2 and DRD2-4 transcripts are differentially expressed in the pituitary, ovary, hypothalamus, as well as in the kidney, whereas the DRD2-3 transcript is widely expressed in all the examined tissues at different levels. Meanwhile, 54 single nucleotide polymorphisms (SNPs) and 4 insert-deletion (indel) variations were identified in the coding region and partial intron region of the goose DRD2 gene. Those findings will help us gain insight into the functions of the DRD2 gene in geese.

Restricted diffusion of dopamine in the rat dorsal striatum

Recent evidence has shown that the dorsal striatum of the rat is arranged as a patchwork of domains that exhibit distinct dopamine kinetics and concentrations. This raises the pressing question of how these distinct domains are maintained, especially if dopamine is able to diffuse through the extracellular space. Diffusion between the domains would eliminate the concentration differences and, thereby, the domains themselves. The present study is a closer examination of dopamine's ability to diffuse in the extracellular space. We used voltammetry to record dopamine overflow in dorsal striatum while stimulating the medial forebrain bundle over a range of stimulus currents and frequencies. We also examined the effects of drugs that modulated the dopamine release (raclopride and quinpirole) and uptake (nomifensine). Examining the details of the temporal features of the evoked profiles reveals no clear evidence for long-distance diffusion of dopamine between fast and slow domains, even though uptake inhibition by nomifensine clearly prolongs the time that dopamine resides in the extracellular space. Our observations support the conclusion that striatal tissue has the capacity to retain dopamine molecules, thereby limiting its tendency to diffuse through the extracellular space.

A microfluidic phenotype analysis system reveals function of sensory and dopaminergic neuron signaling in C. elegans electrotactic swimming behavior

The nematode (worm) C. elegans is a leading multicellular animal model to study neuronal-basis of behavior. Worms respond to a wide range of stimuli and exhibit characteristic movement patterns. Here we describe the use of a microfluidics setup to probe neuronal activity that relies on the innate response of C. elegans to swim toward the cathode in the presence of a DC electric field (termed "electrotaxis"). Using this setup, we examined mutants affecting sensory and dopaminergic neurons and found that their electrotactic responses were defective. Such animals moved with reduced speed (35-80% slower than controls) with intermittent pauses, abnormal turning and slower body bends. A similar phenotype was observed in worms treated with neurotoxins 6-OHDA (6- hydroxy dopamine), MPTP (1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine) and rotenone (20-60% slower). We also found that neurotoxin effects could be suppressed by pre-exposing worms to a known neuroprotective compound acetaminophen. Collectively, these results show that microfluidic electrotaxis can identify alterations in dopamine and amphid neuronal signaling based on swimming responses of C. elegans. Further characterization has revealed that the electrotactic swimming response is highly sensitive and reliable in detecting neuronal abnormalities. Thus, our microfluidics setup could be used to dissect neuronal function and toxin-induced neurodegeneration. Among other applications, the setup promises to facilitate genetic and chemical screenings to identify factors that mediate neuronal signaling and neuroprotection.

The influence of glutamatergic antagonism on motor variability, and comparison to findings in schizophrenia patients

OBJECTIVE

The primary aim of this explorative study was to investigate the influence of the glutamatergic N-methyl-d-aspartate (NMDA) receptor antagonist memantine on motor activity in healthy subjects. Secondarily, we wanted to compare these data to findings in a sample of schizophrenia patients.

METHODS

The healthy subjects acted as their own controls in an open-within-subject design. Motor activity was recorded with an actigraph worn for 24 h in the drug-free, and steady-state memantine conditions, respectively. Motor activity levels for 1-min intervals were analysed by means of both linear and nonlinear methods. The schizophrenia patients were monitored only once, without memantine manipulation.

RESULTS

The root mean square successive differences (RMSSD) and the RMSSD/SD ratio were increased by memantine, and memantine was also associated with lower autocorrelation (lag 1) but in recordings from the right arm only. These movement patterns partly corresponded to those found in a sample of drug-treated schizophrenia patients. Total activity level, standard deviation (SD) and sample entropy were not significantly different in the memantine versus drug-free condition.

CONCLUSION

The findings suggest a role for the NMDA receptor in the regulation of motor activity in healthy individuals as memantine increased the variability in the motor recordings and the alterations between adjacent motor recordings. It is suggested that the findings may be relevant to the role played by glutamate and the NMDA receptor functioning to the motor disturbances in schizophrenia.

Daily subacute paraquat exposure decreases muscle function and substantia nigra dopamine level

The use of the herbicide paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride; PQ) which is widely used in agriculture is known to cause dopaminergic neurotoxicity. However, the mechanisms underlying this effect are not fully understood. This present study investigated the behavioral manifestations, motor coordination, and dopaminergic neurodegeneration following exposure to PQ. Male rats were injected with PQ (10 mg/kg i.p.) daily for three weeks. Rotarod systems were used for measuring locomotor activity and motor coordination. The effects of PQ on dorsiflexor, electrophysiologically-induced muscle contraction were studied. Dopamine concentrations in the ventral mesencephalon were measured by high performance liquid chromatography and the number of dopaminergic neurons in substantia nigra pars compacta was estimated by tyrosine hydroxylase immunohistochemistry. PQ induced difficulty in movement and significant reduction in motor activity and twitch tension at the dorsiflexor skeletal muscle. The number of tyrosine hydroxylase positive neurons was significantly less in the substantia nigra pars compacta and nigral dopamine level was significantly reduced in PQ treated animals (20.4+/-3.4 pg/mg) when compared with control animals (55.0+/-2.4 pg/mg wet tissue). Daily treatment of PQ for three weeks induces selective dopaminergic neuronal loss in the substantia nigra and significant behavioral and peripheral motor deficit effects.

Limbic system pathologies associated with deficiencies and excesses of the trace elements iron, zinc, copper, and selenium

Deficiencies of nutrients such as amino acids, vitamins, lipids, and trace elements during gestation and early infanthood have strong deleterious effects on the development of the limbic system; these effects may be irreversible, even when adequate supplementation is provided at later developmental stages. Recent advances in the neurochemistry of biometals are increasingly establishing the roles of the trace elements iron, copper, zinc, and selenium in a variety of cell functions and are providing insight into the repercussions of deficiencies and excesses of these elements on the development of the central nervous system, especially the limbic system. The limbic system comprises diverse areas with high metabolic demands and differential storage of iron, copper, zinc, and selenium. This review summarizes available evidence suggesting the involvement of these trace elements in pathological disorders of the limbic system.