Transient and sustained effects of dopamine and serotonin signaling in motivation‐related behavior

Pharmacological studies of antidepressants and atypical antipsychotics have suggested a role of dopamine and serotonin signaling in depression. However, depressive symptoms and treatment effects are difficult to explain based simply on brain‐wide decrease or increase in the concentrations of these molecules. Recent animal studies using advanced neuronal manipulation and observation techniques have revealed detailed dopamine and serotonin dynamics that regulate diverse aspects of motivation‐related behavior. Dopamine and serotonin transiently modulate moment‐to‐moment behavior at timescales ranging from sub‐second to minutes and also produce persistent effects, such as reward‐related learning and stress responses that last longer than several days. Transient and sustained effects often exhibit specific roles depending on the projection sites, where distinct synaptic and cellular mechanisms are required to process the neurotransmitters for each transient and sustained timescale. Therefore, it appears that specific aspects of motivation‐related behavior are regulated by distinct synaptic and cellular mechanisms in specific brain regions that underlie the transient and sustained effects of dopamine and serotonin signaling. Recent clinical studies have implied that subjects with depressive symptoms show impaired transient and sustained signaling functions; moreover, they exhibit heterogeneity in depressive symptoms and neuronal dysfunction. Depressive symptoms may be explained by the dysfunction of each transient and sustained signaling mechanism, and distinct patterns of impairment in the relevant mechanisms may explain the heterogeneity of symptoms. Thus, detailed understanding of dopamine and serotonin signaling may provide new insight into depressive symptoms.     

Interaction of nicotinic acetylcholine receptors with dopamine receptors in synaptic plasticity of the mouse insular cortex

The insular cortex plays essential roles in nicotine addiction. However, much is still unknown about its cellular and synaptic mechanisms responsible for nicotine addiction. We have previously shown that in layer 5 pyramidal neurons of the mouse insular cortex, activation of the nicotinic acetylcholine receptors (nAChRs) suppresses synaptic potentiation through enhancing GABAergic synaptic transmission, although it enhances both glutamatergic and GABAergic synaptic transmission. In the present study, we examined whether dopamine receptors might contribute to the nicotine‐induced inhibition of synaptic potentiation. The nicotine‐induced inhibition of synaptic potentiation was decreased in the presence of a D1 dopamine receptor antagonist SCH23390 irrespective of the presence of a D2 dopamine receptor antagonist sulpiride, suggesting that D1 dopamine receptors are involved in nicotine‐induced inhibition. We also investigated how dopamine receptors might contribute to the nAChR‐induced enhancement of glutamatergic and GABAergic synaptic transmission. The nAChR‐induced enhancement of GABAergic synaptic transmission was decreased in the presence of SCH23390 irrespective of the presence of sulpiride, whereas that of glutamatergic synaptic transmission was not altered in the presence of SCH23390 and sulpiride. These results suggest that D1 dopamine receptors are involved in the nAChR‐induced enhancement of GABAergic synaptic transmission while dopamine receptors are not involved in that of glutamatergic synaptic transmission. These observations indicate that the interaction between nAChRs and D1 dopamine receptors plays critical roles in synaptic activities in layer 5 pyramidal neurons of the mouse insular cortex. These insular synaptic changes might be associated with nicotine addiction.     

Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review

ObjectiveSystematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).MethodsPubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.ResultsERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.ConclusionsWhile there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.SignificanceThe review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.     

多巴胺D3受体基因多态性与精神分裂症

目的:探讨沈阳地区汉族人群中多巴胺D3受体基因(DRD3)第一外显子第9密码子A→G单核苷酸置换多态性(Ser9Gly多态)与精神分裂症的关联。方法:采用聚合酶链反应-限制性内切酶片断长度多态性(PCR-RFLP)技术对70例精神分裂症患者、94名健康对照者进行基因分型鉴定。比较患者组与对照组DRD3多态性分布频率、精神分裂症早发组与非早发组基因分布频率差异,并与其他国家人群进行比较。结果:患者组与对照组之间等位基因分布无明显差异,早发组与非早发组亦未发现明显差异,而该位点等位基因分布频率与巴西、英国人群有明显差异。结论:研究人群中未发现DRD3基因Ser9Gly多态与精神分裂症存在明显关联。     

Blunted renal dopaminergic system activity in puromycin aminonucleoside-induced nephrotic syndrome.

BACKGROUND: A primary tubular sodium handling abnormality has been implicated in the edema formation of nephrotic syndrome. Dopamine synthesized by renal proximal tubules behaves as an endogenous natriuretic hormone by activating D(1)-like receptors as a paracrine/autocrine substance. METHODS: We examined the time courses of the urinary excretion of sodium, protein and dopamine in puromycin aminonucleoside (PAN)-treated and control rats. The rats were sacrificed during greatest sodium retention (day 7) as well as during negative sodium balance (day 14) for the evaluation of renal aromatic l-amino acid decarboxylase (AADC) activity, the enzyme responsible for the synthesis of renal dopamine. Also, the influence of volume expansion (VE) and the effects of the D(1)-like agonist fenoldopam (10 microg/kg bw/min) on natriuresis and on proximal tubular Na(+),K(+)-ATPase activity were examined on day 7. RESULTS: The daily urinary excretion of dopamine was decreased in PAN-treated rats, from day 5 and beyond. This was accompanied by a marked decrease in the renal AADC activity, on days 7 and 14. During VE, the fenoldopam-induced decrease in proximal tubular Na(+),K(+)-ATPase activity was more pronounced in PAN-treated rats than in controls. However, the urinary sodium excretion during fenoldopam infusion was markedly increased in control rats but was not altered in PAN-treated animals. CONCLUSION: PAN nephrosis is associated with a blunted renal dopaminergic system activity which may contribute to enhance the proximal tubular Na(+),K(+)-ATPase activity. However, the lack of renal dopamine appears not to be related with the overall renal sodium retention in a state of proteinuria.     

多巴胺受体与其他血压调节系统的交互作用在高血压研究中的地位

肾脏是人体负责钠排泄的重要器官,多巴胺由于其强大的抑制肾脏钠重吸收作用而在原发性高血压的发生、发展中发挥重要作用。多巴胺受体的5个亚型均直接或间接通过与其他血压调节系统的交互作用,参与肾脏钠通道或血压的调节。现就多巴胺受体在调节机体血压和肾脏利钠、利尿作用中所发挥的重要作用作一综述。     

Diencephalic catecholamine neurons (A-11, A-12, A-13, A-14) show divergent changes in the aged rat

The effects of aging on diencephalic (A-11, A-12, A-13, A-14) catecholamine neurons in the F344 male rat were examined with Falck-Hill?rp histofluorescence. In contrast to the age-related increase in A-12 perikaryal fluorescence intensity previously reported (Hoffman and Sladek: Neurobiol. Aging 1:27-37, '80), incertohypothalamic perikarya showed decreased (A-13) or unchanged (A-11, A-14) fluorescence intensity with age. Cell counts of fluorescent A-12 perikarya disclosed a 47% increase in the number of fluorescent A-12 neurons in 30-month-old F344 rats relative to the 3-month-old controls; numbers of A-11 and A-13 fluorescent perikarya decreased with age, but the declines were not statistically significant. It is unlikely that the age-related increase in number of fluorescent A-12 perikarya is the result of proliferation of neurons in the aged F344 rat. Rather, the greater number of fluorescent A-12 perikarya in 30-month-old F344 rats indicates that some A-12 neurons in 3-month-old F344 rats contain levels of dopamine that are subthreshold for detection with the Falck-Hill?rp fluorescence technique, whereas virtually all A-12 perikarya in 30-month-old F344 rats contain detectable quantities of dopamine. These findings suggest that diencephalic catecholamine neurons exhibit divergent changes in transmitter content and cell number that may reflect varying degrees of functional integrity during brain aging.     

Further evidence of dopamine transporter dysregulation in ADHD: a controlled PET imaging study using altropane.

BACKGROUND: The dopamine transporter (DAT) is known to be a key regulator of dopamine, and recent studies of genetics, treatment, and imaging have highlighted the role of DAT in attention-deficit/hyperactivity disorder (ADHD). The findings of in vivo neuroimaging of DAT in ADHD have been somewhat discrepant, however. METHOD: Dopamine transporter binding was measured using a highly selective ligand (C-11 altropane) and positron emission tomography (PET). The sample consisted of 47 well-characterized, treatment-na?ve, nonsmoking, non-comorbid adults with and without ADHD. Additionally, control subjects had few symptoms of ADHD. RESULTS: Results showed significantly increased DAT binding in the right caudate in adults with ADHD compared with matched control subjects without this disorder. CONCLUSIONS: These results confirm abnormal DAT binding in the striatum of adults with ADHD and provide further support that dysregulation of DAT may be an important component of the pathophysiology of ADHD.     

囊泡单胺类转运体功能抑制对PC12细胞的毒性及抗氧化剂的干预

目的：研究囊泡单胺类转运体(VMAT)功能抑制对大鼠嗜铬瘤(PC12)细胞产生的内源性毒性及抗氧化剂的保护作用。方法：用流式细胞仪观察VMAT功能抑制以及不同干预方法对PC12细胞存活的影响和细胞死亡方式。结果：单独加入VMAT抑制剂利血平对PC12细胞无毒性作用；利血平协同多巴胺明显增加多巴胺的毒性，使同样浓度的多巴胺诱发PC12细胞的凋亡率明显增加。加入还原型谷胱甘肽(GSH)、二硫苏糖醇(DTF)和脉冲1号使PC12细胞的生存率明显提高。结论：VMAT功能抑制触发了多巴胺内源性毒性可诱发细胞凋亡，具有抗氧化作用的制剂有细胞保护作用。     

Development of neurochemical separation of ON and OFF channels at retinal ganglion cells

Anatomical and physiological segregation of neurons into ON (brightening detector) and OFF (darkening detector) channels in the retina and subsequent visual system ensure the high sensitivity required for contrast detection and spatial discrimination. This segregation is finest at the visual axis. Neurochemically, ON and OFF ganglion cells at the visual axis seem to be distinguished by different inhibitory transmitters but not excitatory transmitters. Microiontophoretic studies of inhibitory transmitters on the retinal ganglion cells in kittens and adult cats suggest that this neurochemical distinction is poor in immature ganglion cells at the visual axis. Initially both ON and OFF cells seem to be supplied by GABAergic, glycinergic, and catecholaminergic amacrine cells, but in adults, ON cells remain supplied only by GABAergic amacrines, while OFF cells are supplied by glycinergic amacrines. Postnatal elimination of multiple inputs and strengthening of the appropriate inputs, as seen in the central nervous system, also seem to occur at the retinal neurotransmitter synapses during development.