脑微透析在药物监测中的应用

脑微透析是一种微创取样技术,具有多位点、实时取样和可在线等优点,在脑部药物监测中越来越受到关注。脑微透析技术为脑部药物浓度的监测提供了一种有效的新途径,可为新药研发与临床合理用药提供科学依据,在脑部给药系统研究中,特别是药动学及药效学研究中优势显著,具有很好的应用前景。本文综述了有关脑部微透析技术的特点及发展,介绍了脑微透析技术在药物监测研究中的进展,分别归纳了微透析技术在实验动物和临床患者中的应用情况。     

微透析技术在脑缺血动物神经递质研究中的应用

脑内微透析取样技术是一种连续灌注并采集活体动物特定脑区内灌流液的新方法。脑缺血及再灌期间脑细胞外液中兴奋性氨基酸、单胺类递质和乙酰胆碱等神经递质紊乱而致脑损伤。用微透析取样技术研究动物急性脑缺血及再灌后神经递质的动态变化 ,可真实地反映活体动物神经递质的变化情况。本文对近年来国内外有关微透析取样技术及其应用于脑缺血动物神经递质研究进行综述     

前胡提取物对抑郁症模型大鼠脑内中枢单胺类神经递质的影响研究

目的：研究前胡提取物中香豆素类化合物对抑郁症模型大鼠脑内中枢单胺类神经递质的影响。方法以孤养加慢性轻度不可预见性应激方法建立大鼠抑郁症模型,测定糖水消耗、敞箱行为及跳台行为来进行行为学评分,并采用高效液相－电化学方法检测其脑内单胺类神经递质的含量,观察模型大鼠给药前后的变化。结果抑郁症模型组大鼠体质量增长缓慢,蔗糖水消耗量明显下降,水平活动和垂直活动均显著下降,跳台错误次数增加,脑内的去甲肾上腺素、5－羟色胺含量降低（P＜0．05）。30mg／（kg? d）、50mg／（kg? d）剂量前胡提取物能显著改善模型大鼠的行为学变化,增加其脑内去甲肾上腺素、5－羟色胺含量（ P＜0．05）。结论前胡提取物中香豆素类化合物具有抗抑郁作用,对中枢单胺类神经递质的调节作用是其作用机制之一。     

脑微透析技术及其在药动学研究中的应用

脑微透析技术是根据小分子物质可顺浓度梯度自由扩散的原理发展而成的可连续、活体对脑内特定部位细胞外液中生物化学物质进行采集的新型采样技术。凭借自身优点,脑微透析技术越来越多地应用于药动学研究,展现了广阔的应用前景。本文简要综述脑微透析技术原理、特点及其在药动学研究中的应用。     

微透析技术在中药脑保护机理研究中的应用

应用微透析和高效液相色谱技术，分别对脑内灌流叠氮钠（NaN3）所致的脑线粒体损伤大鼠以及双侧颈总动脉结扎再灌引起的不完全脑缺血大鼠的脑细胞外液乙酰胆碱（ACh）、儿茶酚胺和氨基酸类神经递质的水平进行动态监测，探讨天麻方（TMF）脑保护作用的机理。[第一段]     

微透析采样技术及其相关分离检测方法研究进展

微透析技术（microdialysis,MD）是以透析原理和神经科学为基础发展起来的一种新型的生物化学采样技术,它能实现连续在线监测体内外内源性或外源性物质的动态变化。1972年美国耶鲁大学Delgado等首次利用脑微透析推挽灌流技术研究恒河猴脑内神经递质多巴胺的释放实验,开启了微透析技术在神经科学和脑部研究应用领域的大门。自此,     

应用微透析技术和质谱法测定川芎嗪对大鼠脑内乙酰胆碱释放量的影响

本文结合脑内微透析技术与现代分析方法，考察川芎嗪对大鼠脑内乙酰胆碱释放的影响。采用脑内微透析技术进行取样，建立高效液相-串联四极杆质谱方法测定脑透析液中的乙酰胆碱含量。结果显示，川芎嗪皮下给药能够剂量相关地增加大鼠脑内不同脑区中乙酰胆碱的释放。该法能够准确反映药物对大鼠脑内乙酰胆碱释放量的影响，与传统方法相比，具有明显的优势。     

头面部针刺镇痛与中枢神经递质的关系 毁损大白鼠中脑中缝核群对针刺镇痛的影响

在针麻原理的研究中,针刺镇痛与中枢神经递质的关系日益受到重视。根据现有资料,针刺镇痛与中枢5-羟色胺、去甲肾上腺素、多巴胺和乙酰胆碱等多种神经递质都有关系。其中与脑内5-羟色胺能系统的关系尤为密切。总的来说,在针刺镇痛过程中,脑内5-羟色胺(5-HT)及其代谢产物5-羟吲哚乙酸(5HIAA)含量有所升高。用生理学或药理学方法降低5-羟色胺能系统的功能,可减弱针刺镇痛效应,相反,用生理学或药理学方法,加强5-羟色胺能系统的功能,则增强针刺镇痛效应。     

脑电超慢涨落图的正常参考值

近年研究发现，采用多重频谱分析与非线性处理的方法从脑电信号中提取的超慢涨落成分可反映脑内神经递质γ-氨基丁酸(GABA)、谷氨酸(GA)、乙酰胆碱(Ach)、5-羟色胺(5-HT)、去甲肾上腺素(NE)、多巴胺(DA)等的活动，从而使无创伤性检测人在生理和病理生理状态下脑内神经递质的活动成为可能。广东核电集团重庆万丰实业有限公司根据这一原     

脑多肽治疗顽固性癫痫疗效分析

脑多太注射液是促进神经细胞生长的多种高生物活性物质的制剂,富含神经营养因子、神经肽、氨基酸、核糖核酸及神经递质等多种生物活性物质,对各类神经系统疾病发挥综合治疗效应.我们于1997年6月～1999年6月开展添加脑多肽治疗顽固性癫痫的临床试验,观察脑多肽对顽固性癫痫的疗效和副反应,现将结果报告如下:     

In vivo brain microdialysis: advances in neuropsychopharmacology and drug discovery

INTRODUCTION: Microdialysis is an important in vivo sampling technique, useful in the assay of extracellular tissue fluid. The technique has both pre-clinical and clinical applications but is most widely used in neuroscience. The in vivo microdialysis technique allows measurement of neurotransmitters such as acetycholine (ACh), the biogenic amines including dopamine (DA), norepinephrine (NE) and serotonin (5-HT), amino acids such as glutamate (Glu) and gamma aminobutyric acid (GABA), as well as the metabolites of the aforementioned neurotransmitters, and neuropeptides in neuronal extracellular fluid in discrete brain regions of laboratory animals such as rodents and non-human primates. AREAS COVERED: In this review we present a brief overview of the principles and procedures related to in vivo microdialysis and detail the use of this technique in the pre-clinical measurement of drugs designed to be used in the treatment of chemical addiction, neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and as well as psychiatric disorders such as attention-deficit/hyperactivity disorder (ADHD) and schizophrenia. This review offers insight into the tremendous utility and versatility of this technique in pursuing neuropharmacological investigations as well its significant potential in rational drug discovery. EXPERT OPINION: In vivo microdialysis is an extremely versatile technique, routinely used in the neuropharmacological investigation of drugs used for the treatment of neurological disorders. This technique has been a boon in the elucidation of the neurochemical profile and mechanism of action of several classes of drugs especially their effects on neurotransmitter systems. The exploitation and development of this technique for drug discovery in the near future will enable investigational new drug candidates to be rapidly moved into the clinical trial stages and to market thus providing new successful therapies for neurological diseases that are currently in demand.     

Intracerebral microdialysis technique and its application on brain pharmacokinetic-pharmacodynamic study

Intracerebral microdialysis (IC-MD) has been developed as a well-validated and powerful technique for decades. As a practical sampling tool, it can gain the continuous dialysates of endogenous and exogenous substances in extracellular fluid (ECF) of awake freely moving animals. Also, variform IC-MD probes (IC-MDPs) have grown more exquisite. The implantation of the IC-MDP in certain tissue of brain allows monitor drug distribution and measure drug and corresponding neurotransmitters levels in brain ECF after administration for brain pharmacokinetic-pharmacodynamic (B-PK-PD) study. So it is suitable for IC-MD to B-PK-PD study (IC-MD/B-PK-PD). The performance of IC-MD/B-PK-PD can not only elevate the degree of precision and accuracy of experimental data, minimize the individual difference by reduced number of animals, but also give important information for the prediction and optimization of drug effective dose in preclinical study. In this review, we have discussed various IC-MD/B-PK-PD studies of analgesic, antiepileptic and antidepressant drug. The role of IC-MD/B-PK-PD in confirming and assessing the drug effect before clinic trials is highlighted.     

Estimation of in-vivo neurotransmitter release by brain microdialysis: the issue of validity

Although microdialysis is commonly understood as a method of sampling low molecular weight compounds in the extracellular compartment of tissues, this definition appears insufficient to specifically describe brain microdialysis of neurotransmitters. In fact, transmitter overflow from the brain into dialysates is critically dependent upon the composition of the perfusing Ringer. Therefore, the dialysing Ringer not only recovers the transmitter from the extracellular brain fluid but is a main determinant of its in-vivo release. Two types of brain microdialysis are distinguished: quantitative micro-dialysis and conventional microdialysis. Quantitative microdialysis provides an estimate of neurotransmitter concentrations in the extracellular fluid in contact with the probe. However, this information might poorly reflect the kinetics of neurotransmitter release in vivo. Conventional microdialysis involves perfusion at a constant rate with a transmitter-free Ringer, resulting in the formation of a steep neurotransmitter concentration gradient extending from the Ringer into the extracellular fluid. This artificial gradient might be critical for the ability of conventional microdialysis to detect and resolve phasic changes in neurotransmitter release taking place in the implanted area. On the basis of these characteristics, conventional microdialysis of neurotransmitters can be conceptualized as a model of the in-vivo release of neurotransmitters in the brain. As such, the criteria of face-validity, construct-validity and predictive-validity should be applied to select the most appropriate experimental conditions for estimating neurotransmitter release in specific brain areas in relation to behaviour.     

The engagement of brain cytochrome P450 in the metabolism of endogenous neuroactive substrates: a possible role in mental disorders

Abstract

The current state of knowledge indicates that the cerebral cytochrome P450 (CYP) plays an important role in the endogenous metabolism in the brain. Different CYP isoenzymes mediate metabolism of many endogenous substrates such as monoaminergic neurotransmitters, neurosteroids, cholesterol, vitamins and arachidonic acid. Therefore, these enzymes may affect brain development, susceptibility to mental and neurodegenerative diseases and may contribute to their pathophysiology. In addition, they can modify the therapeutic effects of psychoactive drugs at the place of their target action in the brain, where the drugs can act by affecting the metabolism of endogenous substrates. The article focuses on the role of cerebral CYP isoforms in the metabolism of neurotransmitters, neurosteroids, and cholesterol, and their possible involvement in animal behavior, as well as in stress, depression, schizophrenia, cognitive processes, learning, and memory. CYP-mediated alternative pathways of dopamine and serotonin synthesis may have a significant role in the local production of these neurotransmitters in the brain regions where the disturbances of these neurotransmitter systems are observed in depression and schizophrenia. The local alternative synthesis of neurotransmitters may be of great importance in the brain, since dopamine and serotonin do not pass the blood–brain barrier and cannot be supplied from the periphery. In vitro studies indicate that human CYP2D6 catalyzing dopamine and serotonin synthesis is more efficient in these reactions than the rat CYP2D isoforms. It suggests that these alternative pathways may have much greater significance in the human brain but confirmation of these assumptions requires further studies.     

Lactate production and neurotransmitters; evidence from microdialysis studies

Recent studies have found that lactate metabolism plays a significant role in energy supply during acute neural activation in the brain. We will review evidence from microdialysis studies for a relationship between neurotransmitters and lactate production, as revealed in studies of the effects of psychotropic drugs on stress-induced enhancement of extracellular lactate concentrations. Glutamate enhances stress-induced lactate production via activation of N-methyl-D-asparate receptors, and is affected by uptake of glutamate through glutamate transporters. Findings from microdialysis studies suggest that major neurotransmitters, including norepinephrine, dopamine, serotonin, and GABA (via benzodiazepine-receptors) affect lactate production, depending on brain areas, especially during stress. Among these neurotransmitters, glutamate may principally contribute to the regulation of lactate production, with other neurotransmitter systems affecting the extracellular lactate levels in a glutamate-mediated manner. The role for anaerobic metabolism in the supply of energy, as represented by lactate dynamics, deserves further clarification. Monitoring with intracerebral microdialysis is a reliable method for this purpose. Research into this area is likely to provide a novel insight into the mode of action of psychotropic drugs, and the pathophysiology of some of the stress-related mental disorders as well.     

Intracerebral microdialysis: 30 years as a tool for the neuroscientist

1. Microdialysis is an established technique for studying physiological, pharmacological and pathological changes of a wide range of low molecular weight substances in the brain extracellular fluid. Many studies have proven its sensitivity in sampling the extracellular space in discrete brain locations, such as the striatum, and monitoring the action of exogenous substances. 2. The two main areas of application of microdialysis are the recovery of endogenous substances, primarily the neurotransmitters, and the infusion of drugs through the microdialysis cannula (retrodialysis). 3. Microdialysis in awake animals is the tool of choice for studying the relationship between changes in behaviour and neurotransmitters in certain brain areas. In addition, the concomitant recording of the electroencephalogram at the site of microdialysis has been shown to be extremely useful in determining the role of certain neurotransmitters in paroxysmal activity. 4. Clinical applications of microdialysis have included monitoring of ischaemic injury, subarachnoid haemorrhage, trauma and epilepsy. With the recent availability of standardized equipment, the use of microdialysis in the neurological clinic is likely to become more common.     

Consequences of changes in BDNF levels on serotonin neurotransmission, 5-HT transporter expression and function: studies in adult mice hippocampus

In vivo intracerebral microdialysis is an important neurochemical technique that has been applied extensively in genetic and pharmacological studies aimed at investigating the relationship between neurotransmitters. Among the main interests of microdialysis application is the infusion of drugs through the microdialysis probe (reverse dialysis) in awake, freely moving animals. As an example of the relevance of intracerebral microdialysis, this review will focus on our recent neurochemical results showing the impact of Brain-Derived Neurotrophic Factor (BDNF) on serotonergic neurotransmission in basal and stimulated conditions. Indeed, although the elevation of 5-HT outflow induced by chronic administration of selective serotonin reuptake inhibitors (SSRIs) causes an increase in BDNF protein levels and expression (mRNA) in the hippocampus of rodents, the reciprocal interaction has not been demonstrated yet. Thus, the neurochemical sight of this question will be addressed here by examining the consequences of either a constitutive decrease or increase in brain BDNF protein levels on hippocampal extracellular levels of 5-HT in conscious mice.     

Brain microdialysis of isolation-reared mice under freely-moving conditions

Brain microdialysis has become a well established and a widely-used technique for in vivo measurement of extracellular levels of neurotransmitters. However, a single neurotransmitter in the perfusates has been measured in most studies. The present paper describes a simultaneous measurement of serotonin and dopamine release in the prefrontal cortex of mice. Using this technique, we examined the modulation by serotonin(1A) receptors of serotonin, dopamine, and noradrenaline release in the cortex of isolation-reared mice. The isolation-reared mouse is a useful model of complicated mood disorders including phenotypes of anxiety, depression, and aggression. The study shows that isolation rearing selectively decreases the sensitivity of serotonin(1A) receptors to increase dopamine release.     

Stress and the brain: solving the puzzle using microdialysis

Aberrant functioning of the hypothalamic-pituitary-adrenocortical (HPA) axis seems to be involved in depression and anxiety. However, the mechanisms underlying the relationship between stress and mental illness are not completely resolved yet. The therapeutical efficacy of selective serotonin re-uptake inhibitors and benzodiazepines points to a key role of serotonin and gamma-aminobutyric acid (GABA) in depression and anxiety. Thus, it can be hypothesised that stress-induced changes in serotonin and GABA contribute to a dysregulation of the HPA axis and to the development of psychiatric disorders in susceptible subjects. It will, therefore, be crucial to increase our understanding of the effects of stress on serotonin and GABA. Various refinements have made in vivo microdialysis an extremely powerful method to study the highly dynamic neurotransmitter responses in stress physiology and behaviour. Furthermore, microdialysis can also be used to measure free corticosterone levels in the brain and, thus, HPA axis activity and neurotransmission can be monitored concomitantly. Here we review the effects of acute and chronic stress on serotonin and GABA, as assessed by microdialysis, in the hippocampus; a brain structure critically involved in the behavioural and neuroendocrine responses to stress. From the microdialysis data discussed, it can be concluded that both serotonin and GABA in the hippocampus are highly responsive to stress, but also that these responses are shaped by the exact nature of the stressor, i.e. the balance between the psychological and physical aspects of the stressful challenge.     

A validated HPLC-UV method and optimization of sample preparation technique for norepinephrine and serotonin in mouse brain

Abstract

Context: Norepinephrine and serotonin are two important neurotransmitters whose variations in brain are reported to be associated with many common neuropsychiatric disorders. Yet, relevant literature on estimation of monoamines in biological samples using HPLC-UV is limited.

Objective: The present study involves the development of a simultaneous HPLC-UV method for estimation of norepinephrine and serotonin along with optimization of the sample preparation technique.

Materials and methods: Chromatographic separation was achieved by injecting 20?µL of the sample after extraction into Quaternary pump HPLC equipped with C₁₈ column using 0.05% formic acid and acetonitrile (90:10, v/v) as the mobile phase with 1?mL?min^?1 flow rate. The developed method was validated as per the ICH guidelines in terms of linearity, accuracy, repeatability, precision, and robustness.

Results and discussion: The method showed a wide range of linearity (50–4000 and 31.25–4000?ng?mL^?1 for norepinephrine and serotonin, respectively). The recovery was found to be in the range of 86.04–89.01% and 86.43–89.61% for norepinephrine and serotonin, respectively. The results showed low value of %RSD for repeatability, intra and inter-day precision, and robustness studies. Four different methods were used for the extraction of these neurotransmitters and the best one with maximum recovery was ascertained.

Conclusion: Here, we developed and validated a simple, accurate, and reliable method for the estimation of norepinephrine and serotonin in mice brain samples using HPLC-UV. The method was successfully applied to quantify these neurotransmitters in mice brain extracted by optimized sample preparation technique.