Comparative pharmacokinetics of four bioactive components in normal and chronic heart failure rats after oral administration of Qiangxin Lishui Prescription by microdialysis combined with ultra-high-performance liquid chromatography.

Qiangxin Lishui Prescription (QLP) has been clinically applied for treating heart failure with remarkable curative effects. A multi-component pharmacokinetic research is very necessary for determining active substances in it. This study aims to profile the traits and differences in the pharmacokinetics of salvianolic acid B, astragaloside IV, calycosin-7-O-ß-D-glucoside and kaempferol in QLP between normal and chronic heart failure (CHF) rats by microdialysis combined with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Sensitive, selective, and online microdialysis combined with the UHPLC-MS/MS method was successfully established and applied to study the pharmacokinetics of QLP. The pathological condition of CHF could lead to the enhancement of systematic exposure and reduction of the metabolic rate of four bioactive components for better bioavailability and therapeutic efficacy. The pharmacokinetic results will provide data support for the clinical application of QLP.

High-physiological and supra-physiological 1,2-13C2 glucose focal supplementation to the traumatised human brain.

How to optimise glucose metabolism in the traumatised human brain remains unclear, including whether injured brain can metabolise additional glucose when supplied. We studied the effect of microdialysis-delivered 1,2-13C2 glucose at 4 and 8 mmol/L on brain extracellular chemistry using bedside ISCUSflex, and the fate of the 13C label in the 8 mmol/L group using high-resolution NMR of recovered microdialysates, in 20 patients. Compared with unsupplemented perfusion, 4 mmol/L glucose increased extracellular concentrations of pyruvate (17%, p = 0.04) and lactate (19%, p = 0.01), with a small increase in lactate/pyruvate ratio (5%, p = 0.007). Perfusion with 8 mmol/L glucose did not significantly influence extracellular chemistry measured with ISCUSflex, compared to unsupplemented perfusion. These extracellular chemistry changes appeared influenced by the underlying metabolic states of patients' traumatised brains, and the presence of relative neuroglycopaenia. Despite abundant 13C glucose supplementation, NMR revealed only 16.7% 13C enrichment of recovered extracellular lactate; the majority being glycolytic in origin. Furthermore, no 13C enrichment of TCA cycle-derived extracellular glutamine was detected. These findings indicate that a large proportion of extracellular lactate does not originate from local glucose metabolism, and taken together with our earlier studies, suggest that extracellular lactate is an important transitional step in the brain's production of glutamine.

Simultaneous and dynamic measurement of Schisandrol A changes in rat blood and brain and its comparative pharmacokinetic study in control and Parkinson's disease rats by dual-probe in vivo microdialysis.

Schisandrol A (SchA) is the main active ingredient of Schisandra chinensis (Turcz.) Baill., which is a famous traditional Chinese herbal medicine. SchA can penetrate the blood-brain barrier and has a significant neuroprotective effect. A group of multiplexed stable isotope mass tags (MSIMTs, m/z 332, 338, 346, 349, 351, 354, 360, 363, 374 and 377) were synthesized to perform multiplexed stable isotope labeling derivatization (MSILD) of SchA in rat microdialysates and standards. A new magnetic molecularly imprinted polymer was prepared using MSIMT-375-SchA as dummy template. All the 10-plexed derivatives of MSIMTs-SchA can be efficiently and selectively enriched and purified using this adsorbent by magnetic dispersive solid phase extraction (MDSPE) before ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis. It should be pointed out that the MSIMT-346-SchA standard derivative was used as internal standard in the process of MDSPE and UHPLC-MS/MS. On these bases, 9 different rat microdialysate samples can be determined by UHPLC-MS/MS in a single run. The utilization of MSIMTs significantly increased the sensitivity, accuracy, selectivity and analysis throughput. Under the optimized conditions, satisfactory linearity (R2> 0.987), limit of detection (LODs, 0.15-0.26 pg/mL) and lower limit of quantitative (LLOQ, 0.8-2.0 pg/mL) were obtained. Intra- and inter-day precisions were in the range of 2.2% -12.5%, and recoveries 94.2% -106.2%. The matrix effects were very low, and the average derivatization efficiency of 10-plex MSIMTs to SchA was as high as 97.8%. Using the developed dual-probe in vivo microdialysis sampling technique, the proposed analytical method has been applied for comparative pharmacokinetics of SchA in the brain and blood of control and Parkinson's disease (PD) rats.

Comparative pharmacokinetics of seven bioactive components after oral administration of crude and processed Qixue Shuangbu Prescription in chronic heart failure rats by microdialysis combined with UPLC-MS/MS.

ETHNOPHARMACOLOGICAL RELEVANCE: Qixue Shuangbu Prescription (QSP) is a classical traditional Chinese medicine prescription, which has widely used for the treatment of chronic heart failure (CHF). Preliminary clinical studies have shown that the efficacy of processed QSP (P-QSP) in treating CHF is greater than crude QSP (C-QSP). However, the pharmacokinetic characteristics of its major bioactive components under pathological conditions are unclear. AIM OF STUDY: This study aims to compare pharmacokinetics of seven bioactive components after oral administration of C-QSP and P-QSP in CHF model rats. MATERIALS AND METHODS: Ginsenoside Rb1, ginsenoside Re, ginsenoside Rg1, ferulic acid, astragaloside IV, calycosin-7-O-ß-D-glucoside, and paeoniflorin in QSP were used as the target components. CHF model in rats was induced by the intraperitoneal injection of doxorubicin. A microdialysis combined with UPLC-MS/MS method was first established to compare the pharmacokinetics of seven major bioactive components in CHF model rats after oral administration of C-QSP and P-QSP. RESULTS: This method was successfully applied to the pharmacokinetic investigation of seven major components of C-QSP and P-QSP following oral administration in CHF model rats. Compared with the C-QSP group, the Cmax, AUC0-t and AUC0-∞ of ginsenoside Rb1, ginsenoside Re, ginsenoside Rg1, ferulic acid, astragaloside IV and paeoniflorin significantly increased (P < 0.05) in the P-QSP group, which suggested that the absorptivity and bioavailability were increased. Lower T1/2, MRT0-t of ginsenoside Rb1, gerulic acid and higher T1/2, MRT0-t of ginsenoside Rb1, astragaloside IV, paeoniflorin in the P-QSP group, which indicated that eliminated more quickly or slowly, respectively. CONCLUSIONS: The pharmacokinetic parameters of bioactive components were significantly changed for better bioavailability and absorption, longer lasting time elimination, which were beneficial for enhancing therapeutic efficacy in the P-QSP group. This study will provide a new perspective to explain the pharmacokinetic-pharmacodynamic correlation of P-QSP on the treatment of CHF.

LC-MS/MS combined with blood-brain dual channel microdialysis for simultaneous determination of active components of astragali radix-safflower combination and neurotransmitters in rats with cerebral ischemia reperfusion injury: Application in pharmacokinetic and pharmacodynamic study.

BACKGROUND: Astragali Radix-Safflower combination (ARSC) is widely utilized in clinic to treat cerebral ischemia/reperfusion injury (CI/RI). Whereas, there is no in-depth research of the pharmacokinetics (PK) and pharmacodynamics (PD) analysis of ARSC after intragastric administration in rats with CI/RI. PURPOSE: The purpose of this research is to investigate the PK characteristics of eight active ingredients (astragaloside IV, calycosin, calycosin-7-O-ß-glucoside, formononetin, ononin, hydroxysafflor yellow A, syringin and vernine) of ARSC, and the regulation of neurotransmitters disorders, revealing the pharmacodynamic substance basis and the mechanism of ARSC in treating CI/RI from the molecular level. METHODS: We established a new method which based on blood-brain dual channel microdialysis (MD) coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to continuously gather, and determine the components of ARSC and neurotransmitters related to CI/RI in vivo. The collected data were analyzed by sigmoid-Emax function. The neurotransmitters primarily regulated in CI/RI rat were discussed by principal component analysis and the compound most associated with total pharmacodynamics was chosen by partial least squares regression. RESULTS: The validated LC-MS/MS method had specificity and selectivity to simultaneously analyze the concentration of eight active components of ARSC extract and five neurotransmitters of CI/RI rats. The recovery rates of brain MD probe and blood MD probe were stable within six hours. The MD probes recovery rates decreased with the increase of flow rates, but the solution concentration had little effect on the probes recovery rates. It was feasible to correct the recovery rates of probes in vivo by using reverse dialysis method. All eight active ingredients of ARSC could pass across the blood brain barrier after CI/RI. ARSC regulated the release of glutamate (Glu), γ-aminobutyric acid (GABA), dopamine (DA), 5-hydroxytryptamine (5-HT) and aspartic acid (Asp). Notably, astragaloside IV and hydroxysafflor yellow A might have better regulatory effect on neurotransmitters in comparison with other six measured components of ARSC, and Glu was the neurotransmitter mainly regulated in CI/RI rats. CONCLUSION: The ARSC was able to treat CI/RI through ameliorating neurotransmitters disorders. There was a hysteresis between the peaked drug concentration and maximum therapeutic effect of ARSC. The drug effective concentrations range of ASIV, calycosin, calycosin-7-O-ß-glucoside, syringin and vernine in blood microdialysate and calycosin, syringin, vernine in brain microdialysate were narrow, which need be paid attention in clinical use.

[Simultaneous determination of 11 neurotransmitters in brain microdialysis samples from rats by UPLC-MS/MS].

This study established a method for simultaneous determination of 11 neurotransmitters, such as acetylcholine, glutamic acid, glycine, and norepinephrine from rat brain microdialysis samples using UPLC-MS/MS. A total of 20 µL of rat brain dialysate was diluted with 60 µL of acetonitrile-water(4∶1) and centrifuged for 10 min at 10 000 r·min~(-1),and 5 µL was injected into UPLC-MS/MS system for assay. Chromatographic separation was performed on a Waters ACQUITY BEH amide column(2.1 mm×100 mm, 1.7 µm) with gradient elution using acetonitrile/0.2% formic acid-water as mobile phases with a flow rate of 0.35 mL·min~(-1) and column temperature of 35 ℃. The eluate was detected by multiple-reaction monitoring(MRM) scanning with an electrospray ionization source operating in the positive ionization mode with an analysis duration of 3.5 min. The relationship between the recovery rate of 11 neurotransmitters and the perfusion rate or the concentration of neurotransmitters was investigated. Furthermore, the effects of puerarin alone or combined with borneol on the content of 11 neurotransmitters in the striatum of rats were investigated. The results showed the calibration curves displayed good linear regression with coefficients all greater than 0.99 and the lower limit of quantification(LLOQ) less than 12.5 nmol·L~(-1) for each analyte. The within-run and between-run precision(RSD) of the 11 neurotransmitters at low, medium, and high levels was less than 9.3%, and the relative error of the accuracy ranged from-8.4% to 9.5%. The stability, recovery, and matrix effects were in line with the biological sample analysis requirements. As revealed by experimental results, the levels of most neurotransmitters in the brain striatum changed significantly after rats were treated with puerarin as compared with the conditions in the blank group. Except for dopamine and norepinephrine, the degree of changes of other neurotransmitters in the combination group(borneol and puerarin) was less than that of the puerarin group. The established UPLC-MS/MS method could be applied to the quantitative determination of 11 neurotransmitters in microdialysis samples, providing an efficient and useful tool to study neurotransmitter changes in animal models of health and diseases.

Population Pharmacokinetics of Flucloxacillin In Bone and Soft Tissue- Standard Dosing is Not Sufficient to Achieve Therapeutic Concentrations.

PURPOSE: Flucloxacillin is a ß-lactam penicillin commonly used in the treatment of bone and soft tissue infections. In a recent porcine study, we found surprisingly low time for which the free concentration was maintained above the minimal inhibitory concentration (fT>MIC) in bone and soft tissue, following flucloxacillin oral (PO) and intravenous (IV) administration at 1g every 6h (q6h). In addition to plasma, sampling was obtained from subcutaneous tissue, knee joint, cancellous bone and cortical bone, using microdialysis. To identify flucloxacillin dosing regimens that result in theoretically therapeutic concentrations, we developed a population pharmacokinetic (PK) model for the porcine data, and combined it with a human flucloxacillin population PK model for simulations. METHODS: A four-compartment model was developed, and various dosing regimens and modes of administration were simulated. Predicted concentrations were compared to %fT>MIC (0.5 mg/L and 2 mg/L). RESULTS: Continuous infusion (CI) resulted in higher %fT>MIC compared to intermittent administration. For intermittent IV dosing (4, 8 and 12g/24h), fT>MIC (0.5 mg/L) was ≥70% in plasma, and ranged between 42-96% in the sampled tissue in a typical individual. By applying CI, 4g/day was sufficient to achieve ≥98% fT>MIC (0.5 mg/L) in all sampled tissues. For MIC 2 mg/L, ≥50% fT>MIC was only achieved in plasma at CI 8 and 12g/24h and IV 3g q6h. CONCLUSIONS: To reach efficacious flucloxacillin bone and tissue concentrations, dose increment or continuous infusion needs to be considered.

[Pharmacokinetics of three index components of Periploca forrestii in rats by microdialysis combined with UPLC-MS/MS].

The present study established a UPLC-MS/MS method for the content determination of Periploca forrestii microdialysis samples and investigated the pharmacokinetics of three index components of P. forrestii in rats. The effects of flow rate and concentration of perfusate on the recovery rate were investigated by the concentration difference method(increment method and decrement method). The microdialysis samples at different time points were collected, and the concentrations of three index components were determined by UPLC-MS/MS. The actual drug concentrations were corrected with the in vivo recovery rate, and the pharmacokinetic parameters were calculated by WinNonlin 8.2. In the in vitro recovery test, the recovery rate measured by the increment method and the decrement method was inversely proportional to the flow rate and independent of the concentration. The pharmacokinetic parameter AUC_(0-t) values of 3-O-caffeoyl quinic acid, 4-O-caffeoyl quinic acid, and 5-O-caffeoyl quinic acid were(23 911.23±5 679.67),(16 688.43±3 448.45), and(9 677.02±1 606.74) min·µg·L~(-1), respectively. C_(max) values were(170.66±58.02),(121.61±48.14), and(69.69±18.23) µg·L~(-1), respectively. The UPLC-MS/MS method has the advantages of specificity, rapidity, high sensitivity, and accurate quantification. It can simultaneously determine the concentration of 3-O-caffeoyl quinic acid and other two index components in microdialysis samples and is suitable for the pharmacokinetics study of the three index components of P. forrestii in normal rats.

Modulation of the transport of valproic acid through the blood-brain barrier in rats by the Gastrodia elata extracts.

HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE: Valproic acid (VPA) is primarily used as a medicine for the treatment of seizures. Gastrodia elata (G. elata) extract has been used as an alternative medicine for epilepsy patients. Cotreatment with VPA and G. elata extract is commonly prescribed in Taiwan and mainland China. Nevertheless, the mechanism of the blood-brain barrier (BBB) transportation effect of G. elata extract on VPA has not been characterized. AIM OF STUDY: Our hypothesis is that G. elata extract modulates the BBB penetration of VPA through specific transporter transfer. MATERIALS AND METHODS: A validated liquid chromatography-tandem mass spectrometry and multiple microdialysis method was developed to simultaneously monitor VPA in the blood and brain of rats. To investigate the mechanism of BBB modulation by the G. elata extract on VPA in the brain, cyclosporin A, a P-glycoprotein (P-gp) inhibitor and organic anion transporting polypeptide (OATP) inhibitor, was coadministered with the G. elata extract and VPA. RESULTS: The pharmacokinetic results demonstrated that the VPA penetration ratio of the BBB, determined by the area under the concentration curve (AUC) ratio of VPA (AUCbrain/AUCblood), was approximately 0.36. After treatment with the G. elata extract (1 and 3 g/kg, p.o. for 5 consecutive days), the VPA penetration ratios were significantly enhanced to 1.47 and 1.02, respectively. However, in the experimental group coadministered cyclosporin A, the G. elata extract was unable to enhance the BBB transportation of VPA. Instead, the VPA penetration ratio in the brain was suppressed back to 0.38. CONCLUSIONS: The present study reveals that the enhancement effect of the transporter mechanism of G. elata extract on VPA transport into the brain occurs through the OATP transporter but not the P-gp transporter.

Tolerance to neurochemical and behavioral effects of the hallucinogen 25I-NBOMe.

RATIONALE: 4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is a potent serotonin 5-HT2A/2C receptor agonist with hallucinogenic activity. There is no data on the 25I-NBOMe effect on brain neurotransmission and animal performance after chronic administration. OBJECTIVES: We examined the effect of a 7-day treatment with 25I-NBOMe (0.3 mg/kg/day) on neurotransmitters' release and rats' behavior in comparison to acute dose. METHODS: Changes in dopamine (DA), serotonin (5-HT), acetylcholine (ACh), and glutamate release were studied using microdialysis in freely moving rats. The hallucinogenic activity was measured in the wet dog shake (WDS) test. The animal locomotion was examined in the open field (OF) test, short-term memory in the novel object recognition (NOR) test. The anxiogenic/anxiolytic properties of the drug were tested using the light/dark box (LDB) test. RESULTS: Repeated administration of 25I-NBOMe decreased the response to a challenge dose of DA, 5-HT, and glutamatergic neurons in the frontal cortex as well as weakened the hallucinogenic activity in comparison to acute dose. In contrast, striatal and accumbal DA and 5-HT release and accumbal but not striatal glutamate release in response to the challenge dose of 25I-NBOMe was increased in comparison to acute treatment. The ACh release was increased in all brain regions. Behavioral tests showed a motor activity reduction and memory deficiency in comparison to a single dose and induction of anxiety after the drug's chronic and acute administration. CONCLUSIONS: Our findings suggest that multiple injections of 25I-NBOMe induce tolerance to hallucinogenic activity and produce alterations in neurotransmission. 25I-NBOMe effect on short-term memory, locomotor function, and anxiety seems to be the result of complex interactions between neurotransmitter pathways.

The tertiary oxime monoisonitrosoacetone penetrates the brain, reactivates inhibited acetylcholinesterase, and reduces mortality and morbidity following lethal sarin intoxication in guinea pigs.

The brain is a critical target for the toxic action of organophosphorus (OP) inhibitors of acetylcholinesterase (AChE) such as the nerve agent sarin. However, the available oxime antidote 2-PAM only reactivates OP-inhibited AChE in peripheral tissues. Monoisonitrosoacetone (MINA), a tertiary oxime, reportedly reactivates AChE in the central nervous system (CNS). The current study investigated whether MINA would be beneficial as a supplemental oxime treatment in preventing lethality and reducing morbidity following lethal sarin exposure, MINA supplement would improve AChE recovery in the body, and MINA would be detectable in the CNS. Guinea pigs were exposed to sarin and treated with atropine sulfate and 2-PAM at one minute. Additional 2-PAM or MINA was administered at 3, 5, 15, or 30 min after sarin exposure. Survival and morbidity were assessed at 2 and 24 h. AChE activity in brain and peripheral tissues was evaluated one hour after MINA and 2-PAM treatment. An in vivo microdialysis technique was used to determine partitioning of MINA into the brain. A liquid chromatography-tandem mass spectrometry method was developed for the analysis of MINA in microdialysates. MINA-treated animals exhibited significantly higher survival and lower morbidity compared to 2-PAM-treated animals. 2-PAM was significantly more effective in reactivating AChE in peripheral tissues, but only MINA reactivated AChE in the CNS. MINA was found in guinea pig brain microdialysate samples beginning at ~10 min after administration in a dose-related manner. The data strongly suggest that a centrally penetrating oxime could provide significant benefit as an adjunct to atropine and 2-PAM therapy for OP intoxication.

Protein unbound pharmacokinetics of ambroxol in the blood and brains of rats and the interaction of ambroxol with Polygala tenuifolia by multiple microdialysis.

ETHNOPHARMACOLOGICAL RELEVANCE: Ambroxol elevates glucocerebrosidase (GCase) activity and reduces nigrostriatal alpha-synuclein burden to better ameliorate motor function in Parkinson's disease (PD). Polygala tenuifolia is a potential alternative botanical medicine for the treatment of many nonmotor symptoms of PD commonly used in Taiwanese patients. Co-administration of these two medicines pose potential herb-drug interaction. AIM OF THE STUDY: Our hypothesis is that ambroxol and P. tenuifolia may potentially possess herbal drug synergetic effects in the blood and brain. MATERIALS AND METHODS: To investigate this hypothesis, a multiple microdialysis system coupled with validated ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for rat blood and brain samples. Experimental rats were divided into three groups: low-dose and high-dose ambroxol alone (10 mg/kg, i.v. and 30 mg/kg, i.v., respectively) and ambroxol (10 mg/kg, i.v.) pretreated with P. tenuifolia extract (1 g/kg, p.o. for 5 consecutive days). RESULTS: Ambroxol easily penetrated into the brain and reached a maximum concentration in the striatum at approximately 60 min after low- and high-dose treatment. The area under the concentration curve (AUC) ratio increased proportionally at the doses of 10 and 30 mg/kg, which suggested a linear pharmacokinetic manner of ambroxol. The brain penetration of ambroxol was approximately 30-34%, which was defined as the ambroxol AUC blood-to-brain distribution ratio (AUCbrain/AUCblood). The P. tenuifolia extract did not significantly alter the pharmacokinetics of ambroxol in the blood and brain of rats. CONCLUSION: The present study suggests that it is safety without pharmacokinetic interactions for this dosing regimen to use P. tenuifolia extract and ambroxol together.

Contribution of serotonin receptor subtypes to hallucinogenic activity of 25I-NBOMe and to its effect on neurotransmission.

BACKGROUND: 4-Iodo-2,5-dimethoxy-N-(2-methoxybenzyl)phenethylamine (25I-NBOMe) is a potent serotonin (5-HT) receptor agonist with hallucinogenic properties. The aim of our research was to examine the role of the 5-HT2A, 5-HT2C and 5-HT1A serotonin receptor subtypes in 25I-NBOMe hallucinogenic activity and its effect on dopamine (DA), 5-HT and glutamate release in the rat frontal cortex. METHODS: Hallucinogenic activity was investigated using the wet dog shake (WDS) test. The release of DA, 5-HT and glutamate in the rat frontal cortex was studied using a microdialysis in freely moving rats. Neurotransmitter levels were analyzed by HPLC with electrochemical detection. The selective antagonists of the 5-HT2A, 5-HT2C and 5-HT1A serotonin receptor subtypes: M100907, SB242084 and WAY100635, respectively were applied through a microdialysis probe. RESULTS: The WDS response to 25I-NBOMe (1 and 3 mg/kg) was significantly reduced by local administration of M100907 and SB242084 (100 nM). The 25I-NBOMe-induced increase in glutamate, DA and 5-HT release was inhibited by M100907 and SB242084. WAY100635 had no effect on 25I-NBOMe-induced WDS and glutamate release, while it decreased DA and 5-HT release from cortical neuronal terminals. CONCLUSION: The obtained results suggest that 5-HT2A and 5-HT2C receptors play a role in 25I-NBOMe-induced hallucinogenic activity and in glutamate, DA and 5-HT release in the rat frontal cortex as their respective antagonists attenuated the effect of this hallucinogen. The disinhibition of GABA cells by the 5-HT1A receptor antagonist seems to underlie the mechanism of decreased DA and 5-HT release from neuronal terminals in the frontal cortex.

Repeated toluene exposure leads to neuroadaptation in dopamine release mechanisms within the nucleus accumbens core.

BACKGROUND: Intentionally inhaling volatile organic solvent like toluene for its intoxicating effects continues to be a public health concern. While repeated abuse of toluene has deleterious behavioral and health effects, little is known about the actions of toluene on the dopaminergic neurotransmitter system within the central nervous system. METHOD: The present study employed complementary neurochemical techniques of slice fast-scan cyclic voltammetry (FSCV) and in vivo microdialysis, to assess dopamine (DA) dynamics immediately after repeated exposure to 2000- or 4000-ppm toluene. DA D3 autoreceptor functionality, measured by FSCV with pharmacological manipulations and brain tissue content analysis with high performance liquid chromatography, were also used to account for the changes in the DA dynamics. RESULTS: Toluene-exposed mice had decreased stimulated DA release only in the nucleus accumbens core immediately after seven days of repeated exposure. DA uptake was decreased in the core only after 2000-ppm exposure. The differences in stimulated DA release were not attributed to alterations in intraneuronal DA levels as measured by tissue content analysis. Basal extracellular DA levels were not significantly different between the air- and toluene-treated mice. However, following an additional toluene exposure, mice had elevated extracellular DA levels in the nucleus accumbens during recovery. This potentiation in extracellular accumbal DA levels was further heightened following potassium stimulation. The accumbal DA D3 autoreceptor function did not appear to play a role as a potential mediator for these differences. CONCLUSION: Our FSCV and microdialysis results suggest a neuroadaptation in DA release mechanics within the nucleus accumbens, but the exact neuronal mechanism of toluene's impact remains elusive.

Effects of Ice Massage Prior to an Iontophoresis Treatment Using Dexamethasone Sodium Phosphate.

CONTEXT: Low current intensity iontophoresis treatments have increased skin perfusion over 700% from baseline potentially altering drug clearance from or diffusion to the targeted area. OBJECTIVE: To determine the effects of a preceding 10-minute ice massage on subcutaneous dexamethasone sodium phosphate (Dex-P) concentration and skin perfusion during and after a 4-mA iontophoresis treatment. DESIGN: Controlled laboratory study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-four participants (male = 12, female = 12; age = 25.6 [4.5] y, height = 173.9 [8.51] cm, mass = 76.11 [16.84] kg). INTERVENTION(S): Participants were randomly assigned into 2 groups: (1) pretreatment 10-minute ice massage and (2) no pretreatment ice massage. Treatment consisted of an 80-mA·minute (4 mA, 20 min) Dex-P iontophoresis treatment. Microdialysis probes (3 mm deep in the forearm) were used to assess Dex-P, dexamethasone (Dex), and its metabolite (Dex-Met) concentrations. Skin perfusion was measured using laser Doppler flowmetry. MAIN OUTCOME MEASURE(S): Microdialysis samples were collected at baseline, at conclusion of treatment, and every 20 minutes posttreatment for 60 minutes. Samples were analyzed to determine Dex-Total (Dex-Total = Dex-P + Dex + Dex-Met). Skin perfusion was calculated as a percentage change from baseline. A mixed-design analysis of variance was used to determine Dex-Total and skin perfusion difference between groups overtime. RESULTS: There was no difference between groups (P = .476), but [Dex-Total] significantly increased over the course of the iontophoresis and posttreatment time (P < .001). Dex-P was measured in 18 of 24 participants with a mean concentration of 0.67 (1.09) µg/mL. Skin perfusion was significantly greater in the no ice treatment group (P = .002). Peak skin perfusion reached 27.74% (47.49%) and 117.39% (103.45%) from baseline for the ice and no ice groups, respectively. CONCLUSIONS: Ice massage prior to iontophoresis does not alter the tissue [Dex-Total] even with less skin perfusion.

Pharmacokinetic Analysis of Huangqi Guizhi Wuwu Decoction on Blood and Brain Tissue in Rats with Normal and Cerebral Ischemia-Reperfusion Injury by Microdialysis with HPLC-MS/MS.

OBJECTIVE: The aim of our research was to analyze and compare the pharmacokinetics of paeoniflorin, calycosin, calycosin-7-o-ß-d-6-glucoside, and 6-gingerol in the blood and brain tissue of normal and cerebral ischemia-reperfusion injury rats by HPLC-MS/MS method. METHODS: The blood and brain tissue samples of normal and middle cerebral artery occlusion (MCAO) rats were compared. The blood and brain tissue samples were collected by using microdialysis technique. The concentrations of paeoniflorin, calycosin, calycosin-7-o-ß-d-6-glucoside, and 6-gingerol in blood and brain tissues were determined by the HPLC-MS/MS internal standard method. RESULTS: Compared with the normal group, the model group after the administration of the Huangqi Guizhi Wuwu Decoction showed that Cmax blood, AUC0-t blood, and AUC0-inf blood of paeoniflorin were increased, CLblood, t1/2 brain, and Vbrain of paeoniflorin were decreased; Cmaxblood, AUC0-tblood, AUC0-infblood, and average residence time (MRTbrain) of calycosin-7-o-ß-d-6-glucoside were decreased and the CLblood and Cmax brain of calycosin-7-o-ß-d-6-glucoside were increased; Cmax blood of calycosin was decreased, Vblood and Vbrain of calycosin were increased; Cmax blood, AUC0-t blood, AUC0-inf blood, and MRTbrain of 6-gingerol were decreased, CLblood of 6-gingerol was increased. CONCLUSION: This method is simple, rapid, and sensitive. It is suitable for the pharmacokinetic study of Huangqi Guizhi Wuwu Decoction in the blood and brain tissue of rats. Cerebral ischemia-reperfusion injury increased the content of paeoniflorin, calycosin, calycosin-7-o-ß-d-6-glucoside, and 6-gingerol in the blood, affecting the clearance rate of paeoniflorin in the brain, the detention time of calycosin-7-o-ß-d-6-glucoside and the 6-gingerol in the brain. In normal and cerebral ischemia-reperfusion rats, the content of paeoniflorin and 6-gingerol in the blood was higher than that in brain tissue, while the content of calycosin, calycosin-7-o-ß-d-6-glucoside in the brain tissue was higher than that in blood, suggesting that calycosin and calycosin-7-o-ß-d-6-glucoside have brain targeting properties.

Interaction between Mesocortical and Mesothalamic Catecholaminergic Transmissions Associated with NMDA Receptor in the Locus Coeruleus.

Noncompetitive N-methyl-D-aspartate/glutamate receptor (NMDAR) antagonists contribute to the pathophysiology of schizophrenia and mood disorders but improve monoaminergic antidepressant-resistant mood disorder and suicidal ideation. The mechanisms of the double-edged sword clinical action of NMDAR antagonists remained to be clarified. The present study determined the interaction between the NMDAR antagonist (MK801), α1 adrenoceptor antagonist (prazosin), and α2A adrenoceptor agonist (guanfacine) on mesocortical and mesothalamic catecholaminergic transmission, and thalamocortical glutamatergic transmission using multiprobe microdialysis. The inhibition of NMDAR in the locus coeruleus (LC) by local MK801 administration enhanced both the mesocortical noradrenergic and catecholaminergic coreleasing (norepinephrine and dopamine) transmissions. The mesothalamic noradrenergic transmission was also enhanced by local MK801 administration in the LC. These mesocortical and mesothalamic transmissions were activated by intra-LC disinhibition of transmission of γ-aminobutyric acid (GABA) via NMDAR inhibition. Contrastingly, activated mesothalamic noradrenergic transmission by MK801 enhanced intrathalamic GABAergic inhibition via the α1 adrenoceptor, resulting in the suppression of thalamocortical glutamatergic transmission. The thalamocortical glutamatergic terminal stimulated the presynaptically mesocortical catecholaminergic coreleasing terminal in the superficial cortical layers, but did not have contact with the mesocortical selective noradrenergic terminal (which projected terminals to deeper cortical layers). Furthermore, the α2A adrenoceptor suppressed the mesocortical and mesothalamic noradrenergic transmissions somatodendritically in the LC and presynaptically/somatodendritically in the reticular thalamic nucleus (RTN). These discrepancies between the noradrenergic and catecholaminergic transmissions in the mesocortical and mesothalamic pathways probably constitute the double-edged sword clinical action of noncompetitive NMDAR antagonists.

Study on the hepatobiliary behavior of Ermiao wan formula by microdialysis- LC-qTOF-MS.

An improved bile microdialysis sampling technique was established and coupled with liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF-MS) analysis. This method was successfully applied to investigate the metabolic profiles of Ermiao wan (EMW) formula in the bile of Sprague-Dawley (SD) rats. Based on accurate mass information and fragment patterns, 23 alkaloids and lactones metabolites were tentatively identified. Their metabolic pathway involved in glucuronidation, sulfation, hydroxylation and hydrolysis. Because of the high time resolution of microdialysis, the metabolic profiles of EMW were also investigated. Jatrorrhizine, columbamine and other components showed a "double-peak" profiles, suggesting the existence of enterohepatic circulation. The developed microdialysis sampling/ LC-qTOF-MS method provides a simple and efficient research tool for understanding and clarifying the mechanism of hepatobiliary excretion of complex components.

Xylem sap phosphorus sampling using microdialysis-a non-destructive high sampling frequency method tested under laboratory and field conditions.

For a better understanding of plant nutrition processes, it is important to study the flux of nutrients within plants. However, existing xylem sap sampling methods are typically destructive and do not allow for repeated, highly frequent measurements of nutrient concentration. In this paper, we present a novel use of microdialysis (MD) for characterizing xylem sap phosphate (PO43-) concentration as a possible alternative to destructive sampling. First, MD probes were tested under laboratory conditions in vitro, in a stirred solution test, and in vivo, using beech tree stem segments. Exponential decline in the relative recovery (RR) with an increasing MD pumping rate allows for determining an optimal sampling interval (i.e., the maximum amount of sample volume with the minimum required concentration). The RR changed only minimally, with a change in the simulated sap flow velocity during the in vivo stem segment test. This suggests that MD can be applied over a range of naturally occurring sap flow velocities. Differences in the ionic strength between the xylem sap and the perfusate pumped through the MD did not influence the RR. Then, MD was successfully applied in a 24 h field campaign in two beech trees of different ages and allowed for in situ assessments of the diurnal variation of PO43- concentration and (together with xylem flow measurements) flux variability in living trees. Both beech trees exhibited the same diurnal pattern in PO43- concentrations with higher concentrations in the younger tree. The xylem PO43- concentration measured with MD was in the same order of magnitude as that received through destructive sampling in the younger tree. The MD probes did not show a decline in RR after the field application. We showed that MD can be applied to capture the PO43- concentration dynamics in the xylem sap with bihourly resolution under field conditions.

Exploration of chemical composition and absorption characteristics of Chaigui granules based on UHPLC-Q-orbitrap-MS/MS.

Established qualitative analysis method for Chaigui granules based on UHPLC-Q-orbitrap-MS/MS and applied to its absorption properties studies. The LC-MS method was established to identify the structures of the components and metabolites. And then biosamples of rats after administration, e.g. intestinal solution, serum and brain microdialysate, were detected in rats with same method. Xcalibur 3.2 software was used for mass spectrum analysis and identification. Compound discover 3.0 was used for metabolite analysis. 95 chemical constituents were identified from Chaigui granules, including sesquiterpenes, flavonoids, lactones, tannins, organic acids, saponins and so on. 82 components and 11 metabolites were found in intestinal solution. 28 chemical constituents and 32 metabolites were found in serum. 15 chemical constituents were found in brain microdialysate. Vanillic acid, abiflorin, paeoniflorin, 4-hydroxybenzoic acid, lactiflorin, Z-butylidenephthalide, saikosaponin c, saikosaponin a, atractylenolide III, saikosaponin g, saikosaponin b1, sesquiterpenes, butylphthalide, saikosaponin d and glycyrrhetinic acid directly passed through the blood-brain barrier, which might be speculated that Chaigui granule plays an antidepressant role mainly through regulating brain central mechanism and endocrine mechanism, and so on. It is a systematically applicable approach for rapid identification and relative quantitation of Chaigui granules in vivo by UHPLC-Q-orbitrap-MS/MS, provides an important basis for the safety evaluation and rational clinical application of Chaigui granules.