臭椿生物碱canthin-6-one对小鼠镇静催眠作用的研究

摘要 目的：研究臭椿生物碱canthin-6-one对小鼠的镇静催眠作用。方法：选昆明小鼠随机分为空白组、地西泮阳性药物组、canthin-6-one低、中、高给药组（5、10、20 mg?kg^-1），采用阈上剂量和阈下剂量戊巴比妥钠诱导小鼠睡眠，记录入睡小鼠比例、睡眠潜伏期和睡眠持续时间。此外，酶联免疫法测定小鼠脑组织中5-HT、NE、DA和GABA含量。结果：中、高剂量canthin-6-one可使小鼠的站立次数和自主活动次数均明显减少（P＜0.05），可使阈上剂量戊巴比妥钠诱导的小鼠的睡眠潜伏期缩短（P＜0.05）；各剂量组可使阈下剂量戊巴比妥钠诱导的小鼠入睡率提高（P＜0.05）。此外，中、高剂量canthin-6-one也可降低小鼠脑组织中5-HT和NE含量，增加GABA含量（P＜0.05），对DA的含量有影响，但无统计学意义（P＞0.05）。结论：Canthin-6-one有明显的协同戊巴比妥钠改善睡眠作用，其作用与相关神经递质（5-HT、NE、GABA）具有密切关系。     

The Effects of Glutamate and GABA Receptor Antagonists on Nicotine-induced Neurotransmitter Changes in Cognitive Areas*

In the present study, we tested the effects of glutamate and GABA receptor antagonists on nicotine-induced neurotransmitter changes in the hippocampal (dorsal and ventral) and cortical (medial temporal and prefrontal) brain areas of conscious freely moving rats via microdialysis. Both the antagonists and nicotine were administered intracerebrally. The antagonists tested were NMDA, AMPA–kainate, and metabotropic glutamate receptor subtype antagonists (MK801, CNQX, and LY 341495, respectively) and GABA_A and GABA_B receptor subtype antagonists (bicuculline and hydroxysaclofen, respectively). We assayed nicotine-induced changes in dopamine (DA), norepinephrine (NE), serotonin (5-HT), and their metabolites. We found with the antagonists, both decreases and increases in nicotine-induced neurotransmitter responses. In the presence of nicotine all the antagonists (except LY 341495) caused a decrease in DA levels in the regions tested. NE levels were decreased in the cortex by all antagonists. In the hippocampus, GABA antagonists decreased NE levels, as did the metabotropic glutamate antagonist, LY 341495, while the other glutamate antagonists increased NE levels. The results of the 5-HT assay were more variable and dependent on the region and antagonist examined; increases were found slightly more often than decreases. The changes in metabolites were not often parallel with changes in their associated neurotransmitters, indicating that the antagonists also affect the metabolism of the neurotransmitters. The effect of the antagonists in the absence of nicotine was mostly to decrease the level of neurotransmitters, although increases were seen in a few cases. The results suggest that the excitatory glutamatergic- and inhibitory GABAergic-amino acid receptors are both involved in mediating nicotine-induced neurotransmitter responses, and their inhibitory or stimulatory effects are receptor subtype and brain region dependent. * To John P. Blass, an outstanding scientist, clinician and a great friend.     

Hepatocyte transplantation (HTx) corrects selected neurometabolic abnormalities in murine intermediate maple syrup urine disease (iMSUD)

Skvorak et al. [1] demonstrated the therapeutic efficacy of HTx in a murine model of iMSUD, confirming significant metabolic improvement and survival. To determine the effect of HTx on extrahepatic organs, we examined the metabolic effects of HTx in brain from iMSUD animals. Amino acid analysis revealed that HTx corrected increased ornithine, partially corrected depleted glutamine, and revealed a trend toward alloisoleucine correction. For amino acid and monoamine neurotransmitters, decreased GABA was partially corrected with HTx, while the l-histidine dipeptide of GABA, homocarnosine, was decreased in iMSUD mice and hypercorrected following HTx. Elevated branched-chain amino acids (BCAA; leucine, isoleucine, and valine) in MSUD can deplete brain tyrosine and tryptophan (the precursors of monoamine neurotransmitters, dopamine (DA) and serotonin (5-hydroxytryptamine; 5-HT)) through competition via the large neutral amino acid transporter. HTx corrected decreased DA levels and the DA metabolite, 3-methoxytyramine, and partially corrected the DA intermediate 3,4-dihydroxyphenylacetate (DOPAC) and 5-HT levels, despite normal tyrosine and tryptophan levels in iMSUD mouse brain. We further observed enhanced intracellular turnover of both DA and 5-HT in iMSUD mouse brain, both of which partially corrected with HTx. Our results suggest new pathomechanisms of neurotransmitter metabolism in this disorder and support the therapeutic relevance of HTx in iMSUD mice, while providing proof-of-principle that HTx has corrective potential in extrahepatic organs.     

Regional Heterogeneity of Nicotine Effects on Neurotransmitters in Rat Brains <Emphasis Type="Italic">in vivo</Emphasis> at Low Doses

In our recent studies on nicotine-induced changes in neurotransmitters in brain areas associated with cognitive function using a nicotine dose of 0.5 mg/kg administered subcutaneously to conscious freely moving rats, we found changes in dopamine, norepinephrine, and serotonin, and their metabolites, in the areas examined. For the present report we examined changes in these neurotransmitters following administration of lower nicotine doses, to test regional differences in nicotine response and possible threshold levels for some effects of nicotine. The doses used were 0.15 mg/kg and 0.03 mg/kg nicotine administered subcutaneously. Nicotine levels in the brain reached peak values in less than 10 min and decreased with a half-life of about 60 min (0.15 mg/kg) or 30 min (0.03 mg/kg) to values below detection limits (1 ng/g), by the later time points of the 0.03 mg/kg experiments. Nicotine-induced dopamine (DA) increase (and increase in DA metabolites) and decrease in 5-HT levels at 0.15 mg/kg were significant in the cortex, less so in the hippocampus. Norepinephrine (NE) increase at 0.15 mg/kg was much less significant than found previously at 0.5 mg/kg. At a low nicotine dose (0.03 mg/kg), the significant changes observed were a decrease in 5-HT in the hippocampus and small increases of DA and NE in the prefrontal cortex and of NE in the medial temporal cortex. In the nucleus accumbens DA, NE, and 5-HT and their metabolites in the ventral tegmental area, mostly DA and metabolites were increased. We conclude that in areas of cognitive function nicotine-induced DA changes are more concentration dependent than changes in NE or 5-HT, and that there are regional differences in neurotransmitter changes induced by nicotine, with NE changes detectable only in the cortex and 5-HT changes only in the hippocampus at a low nicotine dose, indicating significant regional variation in sensitivity to nicotine-induced neurotransmitter changes in brain areas associated with cognitive function. The decrease in 5-HT shows that nicotine also has indirect effects caused by neurotransmitters released by nicotine. The effects of low nicotine dose are more significant in areas of reward function, indicating differences in sensitivity between cognitive and reward functions.     

非人灵长类动物模型睡眠研究在神经精神疾病的早期诊断和药效评价中的作用

清醒-睡眠的周期性调节需要众多单胺类神经递质(5-HT、NE、DA等)、乙酰胆碱等兴奋性神经递质以及GABA等抑制性神经递质的参与。这些递质系统的异常不仅会导致睡眠周期紊乱,还与一系列的精神性和神经退行性疾病相关。睡眠异常被认为是抑郁症、帕金森氏病等神经系统疾病发生的早期预警信号。相比起低等哺乳动物,非人灵长类动物的睡眠与人类的睡眠具有更好的可比性。近来,利用非人灵长类动物来建立神经精神疾病模型的研究已取得明显进展。在建模的同时监测动物的睡眠状况,有助于我们进一步了解睡眠在这些疾病早期诊断和发展过程中的作用,为疾病的早期诊断、治疗和药效评价提供更好的客观依据。     

Effects of Schistocephalus solidus infection on brain monoaminergic activity in female three-spined sticklebacks Gasterosteus aculeatus.

The three-spined stickleback Gasterosteus aculeatus is an intermediate host of the tapeworm Schistocephalus solidus. Changes in predator avoidance, foraging and shoaling behaviour have been reported in sticklebacks infested with S. solidus, but the mechanisms underlying parasite-induced behavioural changes are not understood. Monoamine neurotransmitters are involved in the control of behaviour and central monoaminergic systems are sensitive to various stressors. Thus, the behavioural effects of S. solidus infestation might be a reflection of changes in brain monoaminergic activity in the stickleback host. The concentrations of 5-hydroxytryptamine (5-HT), dopamine (DA), norepinephrine (NE) and their metabolites 5-hydroxy-indoleacetic acid (5-HIAA), homovanilic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured in the telencephalons, hypothalami and brainstems of parasitized and non-parasitized female sticklebacks held in the laboratory. The ratios of 5-HIAA:5-HT were significantly elevated in both the hypothalami and brainstems of infected sticklebacks. The concentrations of 5-HT and NE were significantly reduced in the telencephalons of infected fish as compared with controls, but there was no elevation of metabolite concentrations. The results are consistent with chronic stress in infected fish, but may also reflect other alterations of neuroendocrine status resulting from parasite infection.     

Aquaporin 4 regulates the effects of ovarian hormones on monoamine neurotransmission

Aquaporin 4 (AQP4) is the predominant water channels in the brain of mammals. Our previous study has reported that AQP4 knockout induced sex-specific alterations in neurotransmission, indicating that AQP4 might regulate the interaction between sex hormones and neurotransmission. In the present study, we found that AQP4 knockout decreased the concentrations of estrogen and progestogen. Further study showed that exogenous estrogen decreased DA and 5-HT in cortex, reduced DA and 5-HT in striatum, but increased 5-HT in hippocampus in AQP4+/+ male mice. However, in AQP4-/- male mice, exogenous estrogen almost did not alter the levels of neurotransmitters except for decreasing DA in cortex. In female mice, ovariectomy decreased DA in the striatum of AQP4+/+ mice, but did not alter the levels of DA in AQP4-/- mice. These findings reveal for the first time that AQP4 regulates not only water and ion homeostasis but also the functions of ovarian hormone and neurotransmitter.     

The effect of the deprivation of paradoxical sleep on the rotational and stereotyped behavior induced by selective agonists of the dopamine receptors

The ability of selective D1 and D2 agonists of dopamine (DA) receptors SKE-38393 and Ly-171555 to induce rotational and stereotypes behaviour were studied in rats with unilateral striatal kainic acid lesion before and after procedure of REM sleep deprivation (REMSD) lasting for 5 days. It was found that REMSD SKF-38393 given along induced the ipsilateral rotation. REMSD increased the circling and decreased an oral stereotype simultaneously when SKF-38393 and Ly-171555 were given together. The depletion of brain DA in part with alpha-methyl-p-tyrosine (AMPT) in nondeprived rats fails to influence the rotational behaviour and stereotype when SKF 38393 was injected 30 min following Ly-171555. After REMSD the AMPT pretreatment prevents the rotational behaviour caused by Ly-171555 which restores SKF-38393. The results suggest that prolonged REMSD may induce nonidentical changes in the sensitivity of the postsynaptic D1 and D2 receptors.     

Cerebrospinal fluid monoamine and metabolite concentrations and aggression in rats

In humans and other primates low cerebrospinal fluid (CSF) levels of the major serotonin (5-HT) metabolite 5-hydroxyindoleacetic acid (5-HIAA) have been correlated to high aggressiveness. This finding forms the basis of the 5-HT deficiency hypothesis of aggression. Surprisingly, this correlation has not been confirmed in rodents so far, while manipulation studies aimed to investigate the link between 5-HT and aggressive behaviour are mostly carried out in rodents. In this study the relation between aggression and CSF monoamine and metabolite concentrations was investigated in male Wildtype Groningen rats. In sharp contrast to the hypothesis and our expectation, a clear positive correlation was found between the individual level of trait-like aggressiveness and CSF concentrations of 5-HT, 5-HIAA, norepinephrine (NE), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC). Shortly after the acute display of aggressive behaviour (as a state-like phenomenon), decreased 5-HT levels and an increase in 5-HIAA/5-HT ratio and NE concentrations were found. Surprisingly, pharmacological challenges known to influence 5-HT transmission and aggressive behaviour did not affect CSF 5-HT and 5-HIAA concentrations, only the NE level was increased. Lesioning 5-HT terminals by 5,7-dihydroxytryptamine (5,7-DHT) administration caused a decrease in CSF 5-HT and 5-HIAA, but without affecting aggressive behaviour. The observed positive correlation between CSF 5-HIAA and trait aggressiveness makes it questionable whether a direct extrapolation of neurobiological mechanisms of aggression between species is justified. Interpretation of CSF metabolite levels in terms of activity of neural substrates requires a far more detailed knowledge of the dynamics and kinetics of a neurotransmitter after its release.     

Influences of Chronic Mild Stress Exposure on Motor,Non-Motor Impairments and Neurochemical Variables in Specific Brain Areas of MPTP/Probenecid Induced Neurotoxicity in Mice

Parkinson''s disease (PD) is regarded as a movement disorder mainly affecting the elderly population and occurs due to progressive loss of dopaminergic (DAergic) neurons in nigrostriatal pathway. Patients suffer from non-motor symptoms (NMS) such as depression, anxiety, fatigue and sleep disorders, which are not well focussed in PD research. Depression in PD is a predominant /complex symptom and its pathology lies exterior to the nigrostriatal system. The main aim of this study is to explore the causative or progressive effect of chronic mild stress (CMS), a paradigm developed as an animal model of depression in1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (25 mg/kg. body wt.) with probenecid (250 mg/kg, s.c.) (MPTP/p) induced mice model of PD. After ten i.p. injections (once in 3.5 days for 5 weeks) of MPTP/p or exposure to CMS for 4 weeks, the behavioural (motor and non-motor) impairments, levels and expressions of dopamine (DA), serotonin (5-HT), DAergic markers such as tyrosine hydroxylase (TH), dopamine transporter (DAT), vesicular monoamine transporters—2 (VMAT 2) and α-synuclein in nigrostriatal (striatum (ST) and substantia nigra (SN)) and extra-nigrostriatal (hippocampus, cortex and cerebellum) tissues were analysed. Significantly decreased DA and 5-HT levels, TH, DAT and VMAT 2 expressions and increased motor deficits, anhedonia-like behaviour and α-synuclein expression were found in MPTP/p treated mice. Pre and/or post exposure of CMS to MPTP/p mice further enhanced the MPTP/p induced DA and 5-HT depletion, behaviour abnormalities and protein expressions. Our results could strongly confirm that the exposure of stress after MPTP/p injections worsens the symptoms and neurochemicals status of PD.     

Neurotransmitter, opiodergic system, steroid-hormone interaction and involvement in the replacement therapy of sexual disorders

Dopamine (DA) and serotonin (5-HT) are the neurotransmitters most directly involved in sexual activity. DA plays a stimulatory role while 5-HT has an inhibitory effect. The two monoaminergic systems modulate the secretion of many hormones (GnRH, LH, testosterone, prolactin and endorphins) involved in sexual functional capacity. Furthermore, hormones influence synthesis and storage of brain neurotransmitters. Impotence can often be associated to clinical depression and altered neurotransmitter function. Moreover, stress represents an unbalance between various neurotransmitter systems and can induce impotence especially when disorders of the endorphinic system are present. Replacement therapy is based upon the understanding of these basic concepts. Impotence due to an underlying depressive illness must be treated with dopaminergic antidepressant drugs; while in stressful conditions a good response to the naloxone test is the preliminary criterion to subsequent naltrexone treatment. When a hormonal deficiency has been proved, the hormone replacement therapy is of course highly effective (gonadotropins in hypogonadotropic syndromes, testosterone in aging, etc.). Finally, idiopathic impotence could be treated by DA agonist and/or 5-HT antagonist drugs either alone or better yet in association with psychotherapy.     

Arginine vasopressin induces periaqueductal gray release of enkephalin and endorphin relating to pain modulation in the rat

Previous study has proven that microinjection of arginine vasopressin (AVP) into periaqueductal gray (PAG) raises the pain threshold, in which the antinociceptive effect of AVP can be reversed by PAG pretreatment with V2 rather than V1 or opiate receptor antagonist. The present work investigated the AVP effect on endogenous opiate peptides, oxytocin (OXT) and classical neurotransmitters in the rat PAG. The results showed that AVP elevated the concentrations of leucine-enkephalin (L-Ek), methionine-enkephalin (M-Ek) and beta-endorphin (beta-Ep), but did not change the concentrations of dynorphinA(1-13) (DynA(1-13)), OXT, classical neurotransmitters including achetylcholine (Ach), choline (Ch), serotonin (5-HT), gamma-aminobutyric acid (GABA), glutamate (Glu), dopamine (DA), norepinephrine (NE) and epinephrine (E), and their metabolic products in PAG perfusion liquid. Pain stimulation increased the concentrations of AVP, L-EK, M-Ek, beta-Ep, 5-HT and 5-HIAA (5-HT metabolic product), but did not influence the concentrations of DynA(1-13), OXT, the other classical neurotransmitters and their metabolic products. PAG pretreatment with naloxone - an opiate receptor antagonist completely attenuated the pain threshold increase induced by PAG administration of AVP, but local pretreatment of OXT or classical neurotransmitter receptor antagonist did not influence the pain threshold increase induced by PAG administration of AVP. The data suggested that AVP in PAG could induce the local release of enkephalin and endorphin rather than dynophin, OXT and classical neurotransmitters to participate in pain modulation.     

Effects of acute 17alpha-methyltestosterone,acute 17beta-estradiol,and chronic 17alpha-methyltestosterone on dopamine,norepinephrine and serotonin levels in the pituitary,hypothalamus and telencephalon of rainbow trout (Oncorhynchus mykiss)

This study investigated: (a) the effects of acute 17alpha-methyltestosterone (MT) or 17beta-estradiol (E(2)) administration on norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3,4, dihydroxyphenylacetic acid (DOPAC), and 5-hydroxyindoleacetic acid (5-HIAA) contents in the hypothalamus, telencephalon and pituitary of previtellogenic female rainbow trout Oncorhynchus mykiss, and (b) the effects of chronic MT administration on the levels of these neurotransmitters in these brain regions in immature male rainbow trout. The acute administration of MT induced a significant decrease in pituitary levels of DOPAC as well as in the DOPAC/DA ratio. On the other hand, the acute administration of E(2) induced an increase in pituitary 5-HT levels as well as a decrease in the 5-HIAA/5-HT ratio. In a second experiment, 20 mg MT per kilogram body weight was implanted for 10, 20 or 40 days into sexually immature male rainbow trout. Implanted rainbow trout showed increased testosterone and decreased E(2) levels. In the pituitary, MT induced long-term decreases in NE, DA, DOPAC and 5-HT levels, as well as in the DOPAC/DA ratio. Hypothalamic and telencephalic DA, NE and 5-HT levels were not affected by MT implantation. However, 5-HIAA levels and the 5-HIAA/5-HT ratio were reduced by MT implantation in both brain regions. These results show that chronic treatment with MT exerts both long-term and region-specific effects on NE, DA, and 5-HT contents and metabolism, and thus that this androgen could inhibit pituitary catecholamine and 5-HT synthesis. A possible role for testosterone in the control of pituitary dopaminergic activity and gonadotropin II release is also discussed.     

Nicotine-Induced Changes in Neurotransmitter Levels in Brain Areas Associated with Cognitive Function

Nicotine, one of the most widespread drugs of abuse, has long been shown to impact areas of the brain involved in addiction and reward. Recent research, however, has begun to explore the positive effects that nicotine may have on learning and memory. The mechanisms by which nicotine interacts with areas of cognitive function are relatively unknown. Therefore, this paper is part of an ongoing study to evaluate regional effects of nicotine enhancement of cognitive function. Nicotine-induced changes in the levels of three neurotransmitters, dopamine (DA), serotonin (5-HT), norepinepherine (NE), their metabolites, homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), and their precursor, L-DOPA, were evaluated in the ventral and dorsal hippocampus (VH and DH), prefrontal and medial temporal cortex (PFC and MTC), and the ventral tegmental area (VTA) using in vivo microdialysis in awake, freely moving, male Sprague-Dawley rats. The animals were treated with acute nicotine (0.5 mg/kg, s.c.) halfway through the 300-min experimental period. The reuptake blockers, desipramine (100 microM) and fluoxetine (30 microM), were given to increase the levels of NE and 5-HT so that they could be detected. Overall, a nicotine-induced DA increase was found in some areas, and this increase was potentiated by desipramine and fluoxetine. The two DA metabolites, HVA and DOPAC, increased in all the areas throughout the experiments, both with and without the inhibitors, indicating a rapid metabolism of the released DA. The increase in these metabolites was greater than the increase in DA. 5-HT was increased in the DH, MTC, and VTA in the presence of fluoxetine; its metabolite, 5-HIAA, was increased in the presence and absence of fluoxetine. Except in the VTA, NE levels increased to a similar extent with desipramine and fluoxetine. Overall, nicotine appeared to increase the release and turnover of these three neurotransmitters, which was indicated by significant increases in their metabolites. Furthermore, DA, and especially HVA and DOPAC, increased for the 150 min following nicotine administration; 5-HT and NE changes were shorter in duration. As gas chromatography experiments showed that nicotine levels in the brain decreased by 75% after 150 min, this may indicate that DA is more susceptible to lower levels of nicotine than 5-HT or NE. In conclusion, acute nicotine administration caused alterations in the levels of DA, 5-HT, and NE, and in the metabolism of DA and 5-HT, in brain areas that are involved in cognitive processes.     

Distress calls of the greater short-nosed fruit bat Cynopterus sphinx activate hypothalamic-pituitary-adrenal (HPA) axis in conspecifics

In a stressful situation, greater short-nosed fruit bats (Cynopterus sphinx) emit audible vocalization either to warn or to inform conspecifics. We examined the effect of distress calls on bats emitting the call as well as the bats receiving the distress signal through analysis of the hypothalamic-pituitary-adrenal axis and catacholaminargic systems. We measured the levels of neurotransmitters [serotonin (5-HT), dopamine (DA), norepinephrine (NE)] and stress hormones [(adrenocorticotropic hormone (ACTH) and corticosterone (CORT)]. Our results showed that distress call emission elevated the level of ACTH and CORT, as well as 5-HT, DA and NE in the amygdala, for both the call emitting bat and the responding bat. Subsequently, we observed increased activity of glucocorticoid receptor and its steroid receptor co-activator (SRC-1). An expression of SRC-1 was up-regulated in the distress call emitter only, whereas it was at a similar level in both the call responder and silent bats. These findings suggest that bats emitting distress calls and also bats responding to such calls have similar neurotransmitter expression patterns, and may react similarly in response to stress.     

两种吗啡依赖大鼠模型脑内单胺神经递质水平的比较

目的通过对吗啡诱导的躯体依赖与精神依赖两种大鼠模型脑内单胺类递质水平的比较,探讨其在吗啡依赖形成中的作用。方法采用剂量递增法复制吗啡依赖大鼠模型,然后用纳洛酮催促,引起躯体戒断症状。连续给予吗啡（5mg／kg,ip）6d,引起大鼠产生显著的条件性位置偏爱效应。脑组织去甲肾上腺素（NE）、5-羟色胺（5-HT）和多巴胺（DA）含量采用荧光分光光度法测定。结果吗啡依赖大鼠催促戒断后脑内NE和5-HT水平明显升高,DA水平下降。吗啡在引起大鼠明显位置偏爱的同时,使大鼠脑内DA和5-HT水平显著升高,NE无明显改变。结论吗啡依赖的形成和戒断与脑内单胺神经递质有密切关系,吗啡依赖的躯体戒断症状与NE升高有关,而吗啡诱导的精神依赖则与脑内DA水平升高有关。     

Exposure to extremely low-frequency magnetic field restores spinal cord injury-induced tonic pain and its related neurotransmitter concentration in the brain

Spinal cord injury (SCI) is unequivocally reported to produce hyperalgesia to phasic stimuli, while both hyper- and hypoalgesia to tonic stimuli. The former is spinally mediated and the latter centrally. Besides, its management is unsatisfactory. We report the effect of magnetic field (MF; 17.96 μT, 50 Hz) on tonic pain behavior and related neurotransmitters in the brain of complete thoracic (T13) SCI rats at week 8. Adult male Wistar rats were divided into Sham, SCI and SCI+MF groups. Formalin-pain behavior was compared utilizing 5 min block pain rating (PR), 60 min session-PR, time spent in various categories of increasing pain (T0–T3) and flinch incidences. Serotonin (5-HT), dopamine (DA), norepinepherine (NE), gamma-aminobutyric acid (GABA), glutamate and glycine were estimated in brain tissue by liquid chromatography–mass spectrometry. Session-PR, block-PR and number of flinches were significantly lower, while time spent in categories 0–1 was higher in the SCI versus Sham group. These parameters were comparable in the SCI+MF versus Sham group. 5-HT concentration in cortex, remaining forebrain areas and brain stem (BS), was lower while GABA and NE were higher in BS of SCI, which were comparable with Sham in the SCI+MF group. The concentration of DA, glutamate and glycine was comparable amongst the groups. The data indicate significant hypoalgesia in formalin pain while increased in GABA, NE and decreased in 5-HT post-SCI, which were restored in the SCI+MF group. We suggest beneficial effect of chronic (2 h/day × 8 weeks) exposure to MF (50 Hz, 17.96 μT) on tonic pain that is mediated by 5-HT, GABA and NE in complete SCI rats.     

Coloboma Hyperactive Mutant Mice Exhibit Regional and Transmitter-Specific Deficits in Neurotransmission

Abstract: The mouse mutant coloboma ( Cm /+), which exhibits profound spontaneous hyperactivity and bears a deletion mutation on chromosome 2, including the gene encoding synaptosomal protein SNAP-25, has been proposed to model aspects of attention-deficit hyperactivity disorder. Increasing evidence suggests a crucial role for SNAP-25 in the release of both classical neurotransmitters and neuropeptides. In the present study, we compared the release of specific neurotransmitters in vitro from synaptosomes and slices of selected brain regions from Cm /+ mice with that of +/+ mice. The release of dopamine (DA) and serotonin (5-HT) from striatum, and of arginine vasopressin and corticotropin-releasing factor from hypothalamus and amygdala is calcium-dependent. Glutamate release from and content in cortical synaptosomes of Cm /+ mice are greatly reduced, which might contribute to the learning deficits in these mutants. In dorsal striatum of Cm /+ mutants, but not ventral striatum, KCI-induced release of DA is completely blocked and that of 5-HT is significantly attenuated, suggesting that striatal DA and 5-HT deficiencies may be involved in hyperactivity. Further, although acetylcholine failed to induce hypothalamic corticotropin-releasing factor release from Cm /+ slices, restraint stress increased plasma corticosterone levels in Cm /+ mice to a significantly higher level than in +/+ mice, suggesting an important role for arginine vasopressin in hypothalamic-pituitary-adrenal axis activation. These results suggest that reduced SNAP-25 expression may contribute to a region-specific and neurotransmitter-specific deficiency in neurotransmitter release.     

Putative nociceptive neurotransmitters in the mesencephalic reticular formation

The neurotransmitter(s) involved in the transmission of nociceptive information in the mesencephalic reticular formation (MRF) of the rat have not been identified. Acetylcholine (ACh), substance P (SP), neurotensin (NT), norepinephrine (NE) and dopamine (DA) have all been implicated as putative neurotransmitters involved in nociception. All of these compounds were microiontophoretically administered in the MRF of rats to determine which, if any, mimicked the effects produced by a nociceptive stimulus (foot pinch). This is only one of several criteria that a substance should meet to be considered a nociceptive neurotransmitter in the MRF. ACh and NE mimicked the effects of the nociceptive stimulus in 61% and 67% respectively of the cells tested; NT, DA and SP mimicked the effects of the nociceptive stimulus less frequently (33%, 30%, 23% respectively). Therefore, the nociceptive neurotransmitters in the MRF appear to be ACh and NE; NT, DA and SP may be neurotransmitters with a less important role in nociception in the MRF.     

Determination of dansylated monoamine and amino acid neurotransmitters and their metabolites in human plasma by liquid chromatography-electrospray ionization tandem mass spectrometry

The determination of neurotransmitters (NTs) and their metabolites facilitates better understanding of complex neurobiology in the central nervous system disorders and has expanding uses in many other fields. We present a liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI/MS/MS) method for the quantification of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), norepinephrine (NE), vanillymandelic acid (VMA), 3-methoxy-4-hydroxy phenylglycol (MHPG), 5-hydroxytryptamine (5-HT), 5-hydroxyindole-3-acetic acid (5-HIAA), glutamate (Glu), and γ-aminobutyric acid (GABA). The NTs and their metabolites were dansylated and analyzed by an LC gradient on a C18 column on-line with a tandem mass spectrometer. This method exhibited excellent linearity for all of the analytes with regression coefficients higher than 0.99. The lower limit of quantification (LLOQ) values for DA, DOPAC, HVA, NE, VMA, MHPG, 5-HT, 5-HIAA, Glu, and GABA were 0.57, 0.37, 0.35, 0.40, 0.35, 0.91, 0.27, 0.43, 0.65, and 1.62 pmol/ml, respectively. The precision results were expressed as coefficients of variation (CVs), ranging from 1.5% to 13.6% for intraassay and from 2.9% to 13.7% for the interassay. This novel LC-ESI/MS/MS approach is precise, highly sensitive, specific, and sufficiently simple. It can provide an alternative method for the quantification of the NTs and their metabolites in human plasma.