Selective corticotropin-releasing factor type 1 receptor antagonist blocks conditioned fear-induced release of noradrenaline in the hypothalamic paraventricular nucleus of rats

The effects of conditioned fear on the release of noradrenaline in the hypothalamic paraventricular nucleus (PVN) and the involvement of corticotropin-releasing factor (CRF) receptor type 1 (CRFR1) in conditioned fear-induced changes in noradrenaline release were examined by intracerebral microdialysis in rats. Conditioned fear was produced by placing animals into a box where they had previously been exposed to a 5-min period of electric footshock, 135 min prior to the start of experiment. Conditioned fear for 20 min produced a significant increase in the release of noradrenaline in the PVN. Intraperitoneal preadministration of a selective nonpeptidic CRFR1 antagonist, CRA1000, completely blocked the conditioned fear-induced release of noradrenaline. These results suggest that CRFR1 is involved in the release of noradrenaline in the hypothalamic PVN induced by conditioned fear.     

Intracerebral Microdialysis and Intracranial Compliance Monitoring of Patients with Traumatic Brain Injury

Objective. The aims of this study were to get an impression of the relationships between intracranial compliance (IC) and Lactate/Pyruvate (L/P) ratio and temperature and L/P ratio, and to determine if patients with low IC had an increased vulnerability for the secondary insult hyperthermia (as reflected in the L/P ratio). The effects of coma treatment on the results were also studied. Methods. Ten TBI patients were monitored for IC, in vivo microdialysis (MD) and bladder temperature. Mean Glasgow Coma Scale (GCS) score was 7 (range 4–10). Three patients underwent induced coma treatment. Three statistical models were used to look at the relationships between IC, temperature and L/P ratio in patients with and without coma. Results. We found that with high temperature L/P ratios increased as IC decreased (P < 0.0001). The patients with coma treatment had significantly higher average L/P ratios (P < 0.02). The effect of IC on the L/P ratio differed by coma treatment (P < 0.02). The temperature effect was not dependent on coma treatment (P < 0.49). Conclusions. These findings suggest the importance of avoiding hyperthermia in TBI patients, especially in patients with low or decreased IC (monitored or anticipated). The present technical solution seems promising for analysis of complex clinical data.     

豚鼠脑在体微透析液氨基酸AccQ·Tag HPLC荧光测定法

目的建立柱前6-氨基喹啉基-N-羟基琥珀酰亚胺基氨基甲酸酯(AQC)衍生高效液相色谱(HPLC)脑在体微透析液中痕量氨基酸的检测方法。方法采用AQC为柱前衍生剂,氨基酸专用分析柱,二元梯度洗脱,荧光检测方法分析样品中的氨基酸。结果该法对脑微透析液中17种氨基酸分离较好,相关系数为0.902 5~0.999 5,平均回收率为94.24%~98.34%,平均CV小于5%。在50 m in内可完成微透析液中17种氨基酸的测定。结论该方法稳定性好、敏感性和准确性较高,适用于豚鼠脑在体微透析液中痕量氨基酸水平的测定。     

beta-Receptor response to noradrenaline in cluster headache. A study of adipose tissue lipolysis

We have previously shown decreased lipolysis in both phases of cluster headache (CH), as an indication of a sympathetic dysregulation. Reduced lipolysis could be a result of diminished beta-receptor sensitivity in adipose tissue. The aim of this study was to measure the lipolytic response to noradrenaline in 10 CH patients in remission and in 10 healthy subjects, to estimate beta-receptor function. Microdialysis technique was used to measure the increase of glycerol, the end-product of lipolysis, during infusion of noradrenaline into the adipose tissue. Noradrenaline infusion resulted in a distinct elevation of glycerol. The average glycerol increase was significantly higher in CH patients (121% +/- 48) than in healthy subjects (77% +/- 41) (P < 0.05), which indicates increased beta-receptor response to noradrenaline in CH patients in remission. This may be due to up-regulated beta-receptor sensitivity, secondary to reduced sympathetic outflow and a primary autonomic disturbance in CH.     

Distinct effects of (R)‐modafinil and its (R)‐ and (S)‐fluoro‐analogs on mesolimbic extracellular dopamine assessed by voltammetry and microdialysis in rats

Psychostimulant use disorders remain an unabated public health concern worldwide, but no FDA approved medications are currently available for treatment. Modafinil (MOD), like cocaine, is a dopamine reuptake inhibitor and one of the few drugs evaluated in clinical trials that has shown promise for the treatment of cocaine or methamphetamine use disorders in some patient subpopulations. Recent structure–activity relationship and preclinical studies on a series of MOD analogs have provided insight into modifications of its chemical structure that may lead to advancements in clinical efficacy. Here, we have tested the effects of the clinically available (R)‐enantiomer of MOD on extracellular dopamine levels in the nucleus accumbens shell, a mesolimbic dopaminergic projection field that plays significant roles in various aspects of psychostimulant use disorders, measured in vivo by fast‐scan cyclic voltammetry and by microdialysis in Sprague‐Dawley rats. We have compared these results with those obtained under identical experimental conditions with two novel and enantiopure bis(F) analogs of MOD, JBG1‐048 and JBG1‐049. The results show that (R)‐modafinil (R‐MOD), JBG1‐048, and JBG1‐049, when administered intravenously with cumulative drug‐doses, will block the dopamine transporter and reduce the clearance rate of dopamine, increasing its extracellular levels. Differences among the compounds in their maximum stimulation of dopamine levels, and in their time course of effects were also observed. These data highlight the mechanistic underpinnings of R‐MOD and its bis(F) analogs as pharmacological tools to guide the discovery of novel medications to treat psychostimulant use disorders.     

Varying the rate of intravenous cocaine infusion influences the temporal dynamics of both drug and dopamine concentrations in the striatum

The faster drugs of abuse reach the brain, the greater is the risk of addiction. Even small differences in the rate of drug delivery can influence outcome. Infusing cocaine intravenously over 5 vs. 90–100 s promotes sensitization to the psychomotor and incentive motivational effects of the drug and preferentially recruits mesocorticolimbic regions. It remains unclear whether these effects are due to differences in how fast and/or how much drug reaches the brain. Here, we predicted that varying the rate of intravenous cocaine infusion between 5 and 90 s produces different rates of rise of brain drug concentrations, while producing similar peak concentrations. Freely moving male Wistar rats received acute intravenous cocaine infusions (2.0 mg/kg/infusion) over 5, 45 and 90 s. We measured cocaine concentrations in the dorsal striatum using rapid‐sampling microdialysis (1 sample/min) and high‐performance liquid chromatography‐tandem mass spectrometry. We also measured extracellular concentrations of dopamine and other neurochemicals. Regardless of infusion rate, acute cocaine did not change concentrations of non‐dopaminergic neurochemicals. Infusion rate did not significantly influence peak concentrations of cocaine or dopamine, but concentrations increased faster following 5‐s infusions. We also assessed psychomotor activity as a function of cocaine infusion rate. Infusion rate did not significantly influence total locomotion, but locomotion increased earlier following 5‐s infusions. Thus, small differences in the rate of cocaine delivery influence both the rate of rise of drug and dopamine concentrations, and psychomotor activity. A faster rate of rise of drug and dopamine concentrations might be an important issue in making rapidly delivered cocaine more addictive.     

Direct angiotensin II type 2 receptor stimulation decreases dopamine synthesis in the rat striatum

A relationship between the central renin angiotensin system and the dopaminergic system has been described in the striatum. However, the role of the angiotensin II type 2 (AT₂) receptor in this interaction has not yet been established. The present study examined the outcome of direct AT₂ receptor stimulation on dopamine (DA) release and synthesis by means of the recently developed nonpeptide AT₂ receptor agonist, compound 21 (C21). The effects of AT₂ receptor agonism on the release of DA and its major metabolite 3,4-dihydroxyphenylacetic acid (DOPAC) and on the activity of tyrosine hydroxylase (TH), the rate-limiting enzyme in the catecholamine biosynthesis, were investigated using in vivo microdialysis. Local administration of C21 (0.1 and 1 μM) resulted in a decrease of the extracellular DOPAC levels, whereas extracellular DA concentrations remained unaltered, suggesting a reduced synthesis of DA. This effect was mediated by the AT₂ receptor since it could be blocked by the AT₂ receptor antagonist PD123319 (1 μM). A similar effect was observed after local striatal (10 nM) as well as systemic (0.3 and 3 mg/kg i.p.) administration of the AT₁ receptor antagonist, candesartan. TH activity as assessed by accumulation of extracellular levels of l-DOPA after inhibition of amino acid decarboxylase with NSD1015, was also reduced after local administration of C21 (0.1 and 1 μM) and candesartan (10 nM). Together, these data suggest that AT₁ and AT₂ receptors in the striatum exert an opposite effect on the modulation of DA synthesis rather than DA release.     

Electrophysiological and neurochemical evidence that pindolol has agonist properties at the 5-HT1A autoreceptor in vivo

1. It has been hypothesized that 5-HT_1A autoreceptor antagonists may enhance the therapeutic efficacy of SSRIs and other antidepressants. Although early clinical trials with the β-adrenoceptor/5-HT₁ ligand, pindolol, were promising, the results of recent more extensive trials have been contradictory. Here we investigated the actions of pindolol at the 5-HT_1A autoreceptor by measuring its effect on 5-HT neuronal activity and release in the anaesthetized rat.
2. Pindolol inhibited the electrical activity of 5-HT neurones in the dorsal raphe nucleus (DRN). This effect was observed in the majority of neurones tested (10/16), was dose-related (0.2–1.0 mg kg⁻¹, i.v.), and was reversed by the 5-HT_1A receptor antagonist, WAY 100635 (0.1 mg kg⁻¹, i.v.), in 6/7 cases tested.
3. Pindolol also inhibited 5-HT neuronal activity when applied microiontophoretically into the DRN in 9/10 neurones tested. This effect of pindolol was current-dependent and blocked by co-application of WAY 100635 (3/3 neurones tested).
4. In microdialysis experiments, pindolol caused a dose-related (0.8 and 4 mg kg⁻¹, i.v.) fall in 5-HT levels in dialysates from the frontal cortex (under conditions where the perfusion medium contained 1 μM citalopram). In rats pretreated with WAY 100635 (0.1 mg kg⁻¹, i.v.), pindolol (4 mg kg⁻¹, i.v.) did not decrease, but rather increased 5-HT levels.
5. We conclude that, under the experimental conditions used in this study, pindolol displays agonist effects at the 5-HT_1A autoreceptor. These data are relevant to previous and ongoing clinical trials of pindolol in depression which are based on the rationale that the drug is an effective 5-HT_1A autoreceptor antagonist.

     

微透析技术在药物局部药动学研究中的应用

目的:对微透析采样技术研究靶向给药制剂局部药动学文献进行了整理和分析。方法:用Web of Science,CNKI数据库检索,检索时间近5年内,关键词为微透析与局部药动学,按照靶向部位进行分析、归纳和总结。结果:微透析采样技术与其他检测技术联用,可在体、实时检测局部组织药物浓度,在心、肝、肺、结肠、脑、皮肤、关节、肿瘤、硬外膜、耳蜗、眼组织部位局部药动学研究中应用广泛。结论:微透析采样技术在靶向制剂体内评价及局部药动学研究方面具有广阔的应用前景。