Clobenpropit,a histamine H3 receptor antagonist/inverse agonist,inhibits [3H]-dopamine uptake by human neuroblastoma SH-SY5Y cells and rat brain synaptosomes

Background

Clobenpropit, a potent antagonist/inverse agonist at the histamine H₃ receptor (H₃R), reduced the cytotoxic action of 6-hydroxydopamine (6-OHDA) in neuroblastoma SH-SY5Y cells transfected with the human H₃R. We therefore set out to study whether this effect involved a receptor-independent action on dopamine transport.

Asparagus racemosus modulates the hypothalamic–pituitary–adrenal axis and brain monoaminergic systems in rats

Abstract

Objectives

Asparagus racemosus (AR) is classified as an adaptogen, an important medicinal plant and food. Even though AR is widely used as food and nutraceutical, it has only been evaluated in the context of experimental disorders. Hence, the present study was designed to evaluate the effect of standardized methanolic extract of AR (MAR) on experimentally un-manipulated animals to observe the per se effects on stress pathways.

Methods

MAR (50, 100, and 200 mg/kg, per oral) was administered for 7 days. Lorazepam (0.5 mg/kg, intraperitoneal) was used as a positive control. On the seventh day, plasma was collected for the estimation of corticosterone (CORT) and norepinephrine (NE), and brain was microdissected into hippocampus, hypothalamus (HYP), pre-frontal cortex, amygdala, and nucleus accumbens to estimate tissue level of monoamines (serotonin, dopamine, and NE), their metabolites, and turnover.

Results

MAR dose-dependently decreased the plasma CORT and NE levels, indicating its effects on the hypothalamic–pituitary–adrenal cortex axis and the sympathetic-noradrenergic system, respectively. MAR increased the levels of all monoamines in the HYP. However, MAR showed region-specific changes in monoamines and their metabolites, and turnover in other brain regions.

Discussion

MAR showed a physiological modulation of the stress pathways. Interestingly, in most brain regions the change in monoaminergic systems was limited by a ceiling effect at a dose of 100 mg/kg. These observations could explain the traditional use of AR as an adaptogen and a functional food.     

Norepinephrine Injection into the Paraventricular Nucleus Induces a Reduced Modification of Eating Behavior and Thermogenesis in Brattleboro Rats

Intake of carbohydrates, lipids, proteins and total calories, temperature of interscapular brown adipose tissue, and oxygen consumption were monitored in vasopressin-containing and vasopressin-deficient rats. These variables were measured after a 20 nmol norepinephrine (NE) or saline injection into the paraventricular nucleus (PVN) of the hypothalamus. NE increased the intake of carbohydrates, lipids and total calories, decreased brown adipose tissue temperature and oxygen consumption in vasopressin-containing rats. NE reduced the intake of carbohydrates, while it increased the consumption of lipids in vasopressin-deficient rats. These findings indicate that vasopressin is involved in the modifications of eating behavioral and thermogenesis induced by NE injection into the hypothalamic PVN.     

正常及妊娠期高血压疾病胎盘组织中单胺类递质的相关研究

目的:通过对正常孕妇及妊娠期高血压疾病孕妇胎盘组织中去甲肾上腺素(NE)、5-羟色胺(5-HT)及多巴胺(DA)的测定,探讨其与妊娠期高血压疾病发病的关系。方法:应用免疫组织化学(免疫组化)链霉素抗生物素-过氧化物酶法,对31例正常早、中、晚孕妇女(正常孕妇组),及38例妊娠高血压、轻度子痫前期、重度子痫前期孕妇的胎盘组织进行NE和DA定位及定量。结果:①定位:正常孕妇组中,早期孕妇的胚胎绒毛滋养细胞NE、DA及5-HT免疫反应呈现强阳性,定位于细胞滋养细胞的细胞膜及细胞浆中;中、晚期孕妇为阳性,定位于合体滋养细胞的细胞膜及细胞浆,以及毛细血管内皮。妊娠期高血压疾病孕妇组定位同正常组。②定量:正常孕妇组NE由孕早期的1.595±0.018降至中、晚期的1.488±0.019和1.419±0.014(P<0.01);DA由孕早期的1.552±0.067,降至中、晚期的1.369±0.051和1.302±0.013(P<0.01),5-HT由孕早期的1.497±0.022升至中、晚期的1.538±0.017和1.554±0.013(P<0.01)。妊娠期高血压疾病组依据病情程度不同DA依次为1.378±0.029、1.305±0.023和1.237±0.024(P<0.01);NE依次为1.494±0.018、1.624±0.014和1.917±0.044(P<0.01),5-HT依次为1.411±0.034、1.374±0.017和1.324±0.014(P<0.01)。结论:正常孕妇组孕早期胎盘组织单胺类递质定位于绒毛滋养细胞中,于孕中、晚期则定位于合体滋养细胞中,正常孕妇组NE及DA含量随孕周增加而逐渐降低,5-HT逐渐升高。妊娠期高血压疾病孕妇组胎盘组织的定位同正常孕妇组的孕晚期相同,NE及5-HT含量随妊娠期高血压疾病病情加重而逐渐升高,DA含量则相反。     

Preclinical pharmacology of F-98214-TA, a novel potent serotonin and norepinephrine uptake inhibitor with antidepressant and anxiolytic properties

Rationale Serotonin (5-HT) and norepinephrine (NE) re-uptake inhibitors (SNRIs) have been proposed to have a higher efficacy and/or faster onset of action than previously available antidepressants. Objectives We examined in biochemical, electrophysiological and behavioural assays the antidepressant properties of (S)-(−)-4-[(3-fluorophenoxy)-phenyl]methyl-piperidine (F-98214-TA), a compound that displays very high affinity for 5-HT and NE transporters. Results F-98214-TA potently inhibited the uptake of both 5-HT and NE into rat brain synaptosomes (IC₅₀=1.9 and 11.2 nM, respectively) and decreased the electrical activity of dorsal raphe serotonergic neurones (ED₅₀=530.3 μg/kg i.v.), an effect completely abolished by the 5-HT_1A antagonist WAY100,635. In acute behavioural assays in mice, the orally administered compound potentiated the 5-hydroxy-tryptophan (5-HTP)-induced syndrome [minimal effective dose (MED)=10 mg/kg], antagonized the hypothermia induced by a high dose of apomorphine (ED₅₀=2 mg/kg) and reduced the immobility in the tail suspension test (MED=10 mg/kg). Moreover, it also decreased the immobility in the forced swimming test in mice and rats (30 mg/kg, p.o.). Chronic administration of F-98214-TA (14 days, 30 mg kg⁻¹ day⁻¹, p.o.) attenuated the hyperactivity induced by olfactory bulbectomy in rats, confirming its antidepressant-like properties. Interestingly, the same dosage regimen significantly increased the social interaction time in rats, suggesting an additional potential anxiolytic activity. In most assays the compound was more potent than fluoxetine, venlafaxine and desipramine. Conclusions F-98214-TA is a novel SNRI that displays greater potency than other reference antidepressants in animal models predictive of antidepressant and anxiolytic activities. A preliminary report of this work was presented at the 30th Annual Meeting of the Society for Neuroscience, New Orleans, LA, 2000.     

Fluoxetine, but not other selective serotonin uptake inhibitors, increases norepinephrine and dopamine extracellular levels in prefrontal cortex

RATIONALE: The selective serotonin uptake inhibitor (SSRI) fluoxetine has been shown to not only increase the extracellular concentrations of serotonin, but also dopamine and norepinephrine extracellular concentrations in rat prefrontal cortex. The effect of other SSRIs on monoamine concentrations in prefrontal cortex has not been thoroughly studied. OBJECTIVE: The aim of this study was to compare the ability of five systemically administered selective serotonin uptake inhibitors to increase acutely the extracellular concentrations of serotonin, norepinephrine and dopamine in rat prefrontal cortex. METHODS: The extracellular concentrations of monoamines were determined in the prefrontal cortex of conscious rats using the microdialysis technique. RESULTS: Fluoxetine, citalopram, fluvoxamine, paroxetine and sertraline similarly increased the extracellular concentrations of serotonin from 2- to 4-fold above baseline. However, only fluoxetine produced robust and sustained increases in extracellular concentrations of norepinephrine and dopamine after acute systemic administration. Fluoxetine at the same dose blocked ex vivo binding to the serotonin transporter, but not the norepinephrine transporter, suggesting that the increase of catecholamines was not due to non-selective blockade of norepinephrine uptake. Prefrontal cortex extracellular concentrations of fluoxetine at the dose that increased extracellular monoamines were 242 nM, a concentration sufficient to block 5-HT(2C) receptors which is a potential mechanism for the fluoxetine-induced increase in catecholamines. CONCLUSION: Amongst the SSRIs examined, only fluoxetine acutely increases extracellular concentrations of norepinephrine and dopamine as well as serotonin in prefrontal cortex, suggesting that fluoxetine is an atypical SSRI.     

Differential regulation of nicotinic receptor-mediated neurotransmitter release following chronic (-)-nicotine administration

The objective of this study was to compare nAChR-mediated neurotransmitter release from slices of rat striatum, frontal cortex and hippocampus following chronic (-)-nicotine (Nic) administration (tartrate salt, 2 mg/kg twice daily for 10 days). Binding studies were also conducted to measure changes in receptor density. Relative to saline-treated animals, the number of nAChRs measured by [(3)H]-cytisine (CYT) binding was significantly increased in all brain regions examined by 15% to 25% following chronic Nic administration. Using a relatively high throughput method to measure neurotransmitter release, we found that Nic, CYT, and (+/-)-epibatidine (EB) evoked similar concentration-dependent striatal [(3)H]-dopamine (DA) and hippocampal [(3)H]-norepinephrine (NE) release from both saline (rank order of potency for [(3)H]-DA: EB>CYT>Nic; pEC(50) values, EB (9 +/- 0.1), CYT (8 +/- 0.13), Nic (7.3 +/- 0.19); rank order potency for [(3)H]-NE: EB>Nic=CYT; pEC(50) values, EB (8 +/- 0.18), Nic (5.5 +/- 0.09), CYT (5.12 +/- 0.1)) -and Nic-treated animals (pEC(50) values [(3)H]-DA, EB (9.5 +/- 0.15), Nic (8 +/- 0.16, CYT (6.6 +/- 0.52); [(3)H]-NE, EB (8.4 +/- 0.23), Nic (5.19 +/- 0.1), CYT (5.18 +/- 0.29)). Although no change in potency was detected between the two treatment groups, the agonist efficacies in both tissues were significantly reduced by approximately 17-54% following chronic Nic administration. In contrast to striatum, treatment with Nic did not affect the maximal [(3)H]-DA response (efficacy) in the frontal cortex. However, as observed in the striatum, no change in agonist potency was observed in the frontal cortex following chronic Nic administration (pEC(50) values, saline; EB (9.2 +/- 0.2), >CYT (6.95 +/- 0.75) = Nic (6.9 +/- 0.16); Nic-treated, EB (9 +/- 0.42)>CYT (6.88 +/- 0.27) = Nic (7.1 +/- 0.17)). Chronic Nic treatment did not significantly affect KCl-evoked [(3)H]-NE release from hippocampus or [(3)H]-DA release from frontal cortex or striatum. Since previous work has demonstrated that different nAChR subtypes display various sensitivities to chronic Nic exposure, we suggest that the subtypes of nAChRs involved in regulating [(3)H]-DA release may be different in the striatum and frontal cortex. These results support findings from earlier studies comparing the pharmacology of nAChR-evoked striatal versus cortical [(3)H]-DA release.     

Cyclooxygenase inhibitors attenuate endothelin ET(B) receptor-mediated contraction in human temporal artery

Phendimetrazine is an effective and widely prescribed appetite suppressant. Preclinical findings show that phendimetrazine displays stimulant properties similar to amphetamine, but few studies have examined the neurochemical mechanism of the drug. In the present work, we characterize the activity of phendimetrazine and its putative metabolites [phenmetrazine, pseudophenmetrazine, and associated stereoisomers] at biogenic amine transporters. All drugs were tested in vitro using assays to measure uptake and release of [3H]dopamine, [3H]norepinephrine, and [3H]serotonin ([3H]5-HT) in rat brain synaptosomes. Selected drugs were tested in vivo using microdialysis to measure extracellular dopamine and serotonin (5-HT) in rat nucleus accumbens. Phendimetrazine itself had no effect on uptake or release of any transmitter. In contrast, the trans-configured N-demethylated metabolite, phenmetrazine, was a potent releaser of [3H]norepinephrine (EC(50)=50 nM) and [3H]dopamine (EC(50)=131 nM). The cis N-demethylated metabolite, pseudophenmetrazine, displayed modest potency at releasing [3H]norepinephrine (EC(50)=514 nM) and blocking [3H]dopamine re-uptake (IC(50)=2630 nM). All drugs tested were inactive or weak in the [3H]5-HT assays. When injected intravenously, phendimetrazine had minimal effects on extracellular transmitter levels, whereas phenmetrazine produced dose-related elevations in extracellular dopamine. The collective findings suggest that phendimetrazine is a "prodrug" that is converted to the active metabolite phenmetrazine, a potent substrate for norepinephrine and dopamine transporters.     

The neurotoxin 2'-NH2-MPTP degenerates serotonin axons and evokes increases in hippocampal BDNF

1-Methyl-4-(2'-aminophenyl)-1,2,3,6-tetrahydropyridine (2'-NH2-MPTP) causes long-term depletions in cortical and hippocampal serotonin (5-HT) and norepinephrine (NE) that are accompanied by acute elevations in glial fibrillary acidic protein (GFAP) and argyrophilia. To further investigate the hypothesis that these changes are reflective of serotonergic and noradrenergic axonal degeneration, 2'-NH2-MPTP was administered to mice and innervation densities were determined immunocytochemically. Regional responses of the neurotrophin, brain-derived neurotrophic factor (BDNF), to putative damage were also assessed. Three days after 2'-NH2-MPTP, 5-HT axons exhibited a beaded, tortuous appearance indicative of ongoing degeneration. At 21 days, numbers of serotonin axons were significantly decreased, with the greatest axonal losses occurring in cortex and hippocampus. Serotonin axons in the amygdala were contrastingly spared long-term damage, as were 5-HT and NE cell bodies in the brain stem. BDNF protein levels were selectively increased in the hippocampus 3 days post-dose and returned to normal 21 days later. These results, in conjunction with previous findings, demonstrate that 2'-NH2-MPTP causes degeneration of serotonergic axons innervating the cortex and hippocampus on par with depletions in neurotransmitter levels. Moreover, damage to the hippocampus, a brain region important for learning and memory, and the modulation of anxiety and stress responsiveness, results in a transitory increase in BDNF.     

微量去甲肾上腺素预处理对大鼠心肌延迟性保护效应的实验研究

目的 :通过在体大鼠心肌缺血 /再灌注 (I/R)模型探讨去甲肾上腺素预处理对I/R心肌的延迟性保护作用。方法 :将实验动物分为假手术、I/R和去甲肾上腺素预处理 (NEPC) 3组 ,分别测定心肌梗塞面积、左室功能 ,观察心肌超微结构及血清肌酸激酶 (CK)及乳酸脱氢酶 (LDH)活性的变化。结果 :预先注入去甲肾上腺素能明显减小I/R所致的心肌梗塞面积 ,改善左室功能 ,保护心肌超微结构 ,增强细胞稳定性减少细胞内蛋白酶的漏出。结论 :去甲肾上腺素预处理可介导延迟性心肌保护效应 ,鉴于该法简便且无明显创伤更易于临床推广应用。