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- Implication of NGF and endocannabinoid signaling in the mechanism of action of sesamol: a multi-target natural compound with therapeutic potential. [JOURNAL ARTICLE]
- Psychopharmacology (Berl) 2013 Apr 27.
RATIONALE:Sesamol, a natural compound with anti-inflammatory, antioxidant and neuroprotective properties, has shown promising antidepressant-like effects. However, its molecular target(s) have not been well defined, which merits further investigation.
OBJECTIVES:Based on the interaction between the neurotrophin and endocannabinoid (eCB) systems and their contribution to emotional reactivity and antidepressant action, we aimed to investigate the involvement of nerve growth factor (NGF) and eCB signalling in the mechanism of action of sesamol.
METHODS:Following acute and 4-week intraperitoneal (i.p.) administration of sesamol (40, 80 and 100 mg/kg), the classical antidepressant amitriptyline (2.5, 5 and 10 mg/kg) or the benzodiazepine flurazepam (5, 10 and 20 mg/kg), brain regional levels of NGF and eCB contents were quantified in rats by Bio-Rad protein assay and isotope-dilution liquid chromatography/mass spectrometry, respectively. In the case of any significant change, the cannabinoid CB1 and CB2 receptor antagonists (AM251 and SR144528) were administered i.p. 30 min prior to the injection of sesamol, amitriptyline or flurazepam.
RESULTS:Following the chronic treatment, sesamol, similar to amitriptyline, resulted in the sustained elevation of NGF and eCB contents in dose-dependent and brain region-specific fashion. Neither acute nor chronic treatment with flurazepam altered brain NGF or eCB contents. Pretreatment with 3 mg/kg AM251, but not SR144528, prevented the elevation of NGF protein levels. AM251 exerted no effect by itself.
CONCLUSIONS:Sesamol, similar to amitriptyline, is able to affect brain NGF and eCB signalling under the regulatory drive of the CB1 receptors.
- Standard additions-dilution method for absolute quantification in voltammetry of microparticles. Application for determining psychoactive 1,4-benzodiazepine and antidepressants drugs as adulterants in phytotherapeutic formulations. [Journal Article]
- J Pharm Biomed Anal 2013 Jun.:159-63.
A standard additions-dilution solid-state electrochemical method for the determination of psychoactive 1,4-benzodiazepine and antidepressants drugs used as adulterants in commercial slimming herbal formulations is described and compared with conventional standard addition method. The proposed method, based on the voltammetry of microparticles approach, permits quantify, via standard additions methodology, 1,4-benzodiazepine and antidepressants drugs in phytotherapeutic formulations with no need of sample dissolution using dilution with a reference electroactive compound. The method was used to measure 1,4-benzobenzodiazepines (clonazepam, flurazepam, alprazolam, midazolam, bromazepam, chlordiazepoxide, lorazepam and diazepam) and antidepressants (bupropion, sertraline, paroxetine and fluoxetine) in slimming formulations that have been commercialized in Brazil.
- Development of an LC-MS/MS method for the simultaneous determination of 25 benzodiazepines and zolpidem in oral fluid and its application to authentic samples from regular drug users. [Journal Article, Research Support, Non-U.S. Gov't]
- J Pharm Biomed Anal 2013 Feb 23.:213-22.
A simple and reliable analytical method was established and validated for the simultaneous determination of 25 benzodiazepines and zolpidem in oral fluid obtained using the Quantisal™ collection device. The samples were prepared by liquid-liquid extraction with ethyl acetate and analyzed using liquid chromatography-tandem mass spectrometry. The validation parameters included limits of detection and quantification (LOD and LOQ), linearity, accuracy and precision, selectivity, recovery, matrix effects and process efficiency. To investigate the variables associated with collection of oral fluid, drug stability and drug recovery in/from the collection device were also determined. The LOD ranged from 0.01 ng/ml to 0.5 ng/ml and the LOQ ranged from 0.1 ng/ml to 0.5 ng/ml. The results of the intra- and inter-day precision and accuracy were satisfactory, i.e., <10% for precision and within ± 10% for accuracy at a low (LOQ of each analyte) and high concentrations (5 ng/ml). In addition, all analytes were stable under the storage condition of below -20°C for 1 month. Drug recoveries from the collection device were more than 80% (81-95%) except those of clonazepam and flunitrazepam, which were unstable in oral fluid. The developed method was successfully applied to authentic oral fluid specimens obtained from psychiatric patients who take benzodiazepines or zolpidem regularly. As a result, alprazolam, clonazepam, diazepam, flunitrazepam, flurazepam, lorazepam, zolpidem and/or their metabolites were detected at 1-18 h after intake of these drugs. This study will be useful for the analysis of oral fluid samples collected in forensic toxicological cases.
- Screening of pharmacologic adulterant classes in herbal formulations using voltammetry of microparticles. [Journal Article, Research Support, Non-U.S. Gov't]
- J Pharm Biomed Anal 2013 Feb 23.:194-204.
A solid state electrochemical method for screening different families of adulterant chemicals illegally added to commercial phytotherapuetic formulations is described. The proposed method, based on the voltammetry of microparticles approach, permits a fast and sensitive way to distinguish between anorexics (amfepramone, fenproporex, sibutramine), benzozodiazepinic anxiolytics (clonazepam, flurazepam, alprazolam, midazolam, medazepam, chlordiazepoxide, diazepam), antidepressants (bupropione, fluoxetine, sertraline, paroxetine), diuretics (hydrochlorothiazide, furosemide, chlortalidone, amiloride, spironolactone), and hypoglycemics (glimepiride, chlorpropamide, glibenclamide) based on characteristic voltammetric signals recorded on solid micro- or nanosamples attached to graphite electrodes immersed into aqueous electrolytes.
- Linking GABA(A) receptor subunits to alcohol-induced conditioned taste aversion and recovery from acute alcohol intoxication. [Journal Article, Research Support, N.I.H., Extramural]
- Neuropharmacology 2013 Apr.:46-56.
GABA type A receptors (GABA(A)-R) are important for ethanol actions and it is of interest to link individual subunits with specific ethanol behaviors. We studied null mutant mice for six different GABA(A)-R subunits (α1, α2, α3, α4, α5 and δ). Only mice lacking the α2 subunit showed reduction of conditioned taste aversion (CTA) to ethanol. These results are in agreement with data from knock-in mice with mutation of the ethanol-sensitive site in the α2-subunit (Blednov et al., 2011). All together, they indicate that aversive property of ethanol is dependent on ethanol action on α2-containing GABA(A)-R. Deletion of the α2-subunit led to faster recovery whereas absence of the α3-subunit slowed recovery from ethanol-induced incoordination (rotarod). Deletion of the other four subunits did not affect this behavior. Similar changes in this behavior for the α2 and α3 null mutants were found for flurazepam motor incoordination. However, no differences in recovery were found in motor-incoordinating effects of an α1-selective modulator (zolpidem) or an α4-selective agonist (gaboxadol). Therefore, recovery of rotarod incoordination is under control of two GABA(A)-R subunits: α2 and α3. For motor activity, α3 null mice demonstrated higher activation by ethanol (1 g/kg) whereas both α2 (-/-) and α3 (-/Y) knockout mice were less sensitive to ethanol-induced reduction of motor activity (1.5 g/kg). These studies demonstrate that the effects of ethanol at GABAergic synapses containing α2 subunit are important for specific behavioral effects of ethanol which may be relevant to the genetic linkage of the α2 subunit with human alcoholism.
- Benzodiazepine treatment induces subtype-specific changes in GABA(A) receptor trafficking and decreases synaptic inhibition. [Journal Article, Research Support, N.I.H., Extramural]
- Proc Natl Acad Sci U S A 2012 Nov 6; 109(45):18595-600.
Benzodiazepines potentiate γ-aminobutyric acid type A receptor (GABA(A)R) activity and are widely prescribed to treat anxiety, insomnia, and seizure disorders. Unfortunately, clinical use of benzodiazepines (BZs) is severely limited by tolerance. The mechanisms leading to BZ tolerance are unknown. BZs bind at the interface between an α and γ subunit of GABA(A)Rs, preferentially enhancing synaptic receptors largely composed of α(1-3, 5), β3, and γ2 subunits. Using confocal imaging and patch-clamp approaches, we show that treatment with the BZ flurazepam decreases GABA(A)R surface levels and the efficacy of neuronal inhibition in hippocampal neurons. A dramatic decrease in surface and total levels of α2 subunit-containing GABA(A)Rs occurred within 24 h of flurazepam treatment, whereas GABA(A)Rs incorporating α1 subunits showed little alteration. The GABA(A)R surface depletion could be reversed by treatment with the BZ antagonist Ro 15-1788. Coincident with decreased GABA(A)R surface levels, flurazepam treatment reduced miniature inhibitory postsynaptic current amplitude, which returned to control levels with acute Ro 15-1788 treatment. GABA(A)R endocytosis and insertion rates were unchanged by flurazepam treatment. Treatment with leupeptin restored flurazepam lowered receptor surface levels, strongly suggesting that flurazepam increases lysosomal degradation of GABA(A)Rs. Together, these data suggest that flurazepam exposure enhances degradation of α2 subunit-containing GABA(A)Rs after their removal from the plasma membrane, leading to a reduction in inhibitory synapse size and number along with a decrease in the efficacy of synaptic inhibition. These reported subtype-specific changes in GABA(A)R trafficking provide significant mechanistic insight into the initial neuroadaptive responses occurring with BZ treatment.
- Effects of diazepam and flumazenil on forebrain ischaemia in a rat model of benzodiazepine tolerance. [Journal Article]
- Br J Anaesth 2012 Dec; 109(6):935-42.
Post-ischaemic benzodiazepine administration is neuroprotective, but chronic administration of benzodiazepines can induce tolerance, such that the neuroprotective effect may be reduced. This study investigated whether benzodiazepine tolerance can worsen ischaemic injury and whether neuroprotection by post-ischaemic benzodiazepine administration is affected by benzodiazepine tolerance. We also investigated whether antagonism of benzodiazepine receptors by flumazenil was able to restore neuroprotection during benzodiazepine tolerance.Experiments were performed in both benzodiazepine-tolerant and naive rats. Benzodiazepine tolerance was indeed by 4 weeks administration of flurazepam. Bilateral carotid artery occlusion (BCAO) was performed to cause cerebral ischaemia. Four experiments were performed: (1) BCAO with no further interventions; (2) BCAO followed by administration of diazepam; (3) administration of flumazenil before BAO; and (4) administration of flumazenil before and diazepam after BCAO. Neurological and histological assessment was performed 5 days after BCAO.Benzodiazepine tolerance did not affect neuronal injury in the CA1 and CA3 regions and dentate gyrus of the hippocampus after severe ischaemic insult, but did worsen neuronal damage when mild ischaemia was applied (P<0.05). Neuroprotective efficacy of post-ischaemic diazepam was not observed under conditions of benzodiazepine tolerance. Flumazenil treatment before BCAO reduced ischaemic neuronal damage exacerbated by benzodiazepine tolerance (P<0.05), and restored neuroprotection by post-ischaemic diazepam (P<0.05), the effect of which was reduced by benzodiazepine tolerance (P<0.05). However, pre-ischaemic flumazenil treatment in naive animals reduced neuroprotection provided by post-ischaemic diazepam (P<0.01-0.05).Benzodiazepine tolerance can worsen ischaemic neuronal injury and abolish the neuroprotection provided by post-ischaemic diazepam. Pre-treatment with flumazenil treatment reversed benzodiazepine tolerance and restored neuroprotection by post-ischaemic diazepam. These findings may suggest that management of patient's risk of developing cerebral ischaemia may need to take into account current use.
- Pentameric ligand-gated ion channel ELIC is activated by GABA and modulated by benzodiazepines. [Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't]
- Proc Natl Acad Sci U S A 2012 Oct 30; 109(44):E3028-34.
GABA(A) receptors are pentameric ligand-gated ion channels involved in fast inhibitory neurotransmission and are allosterically modulated by the anxiolytic, anticonvulsant, and sedative-hypnotic benzodiazepines. Here we show that the prokaryotic homolog ELIC also is activated by GABA and is modulated by benzodiazepines with effects comparable to those at GABA(A) receptors. Crystal structures reveal important features of GABA recognition and indicate that benzodiazepines, depending on their concentration, occupy two possible sites in ELIC. An intrasubunit site is adjacent to the GABA-recognition site but faces the channel vestibule. A second intersubunit site partially overlaps with the GABA site and likely corresponds to a low-affinity benzodiazepine-binding site in GABA(A) receptors that mediates inhibitory effects of the benzodiazepine flurazepam. Our study offers a structural view how GABA and benzodiazepines are recognized at a GABA-activated ion channel.
- Regulation of Ca²⁺/calmodulin-dependent protein kinase II signaling within hippocampal glutamatergic postsynapses during flurazepam withdrawal. [Journal Article, Research Support, N.I.H., Extramural]
- Neural Plast 2012.:405926.
Cessation of one-week oral administration of the benzodiazepine flurazepam (FZP) to rats results in withdrawal anxiety after 1 day of withdrawal. FZP withdrawal is correlated with synaptic incorporation of homomeric GluA1-containing α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) in the proximal stratum radiatum of CA1 neurons. After 2 days of withdrawal, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) phosphorylates GluA1 subunits at Ser(831), increasing channel conductance. Secondary to AMPAR potentiation, GluN2B-containing N-methyl-D-aspartate receptors (NMDARs), known binding partners of CaMKII, are selectively removed from the postsynaptic density (PSD). While activation of synaptic CaMKII is known to involve translocation to the PSD, CaMKII bound to NMDARs may be removed from the PSD. To distinguish these possibilities, the current studies used postembedding immunogold electron microscopy to investigate alterations in CaMKII signaling at CA1 stratum radiatum synapses after 2 days of FZP withdrawal. These studies revealed decreased total, but not autophosphorylated (Thr(286)) CaMKIIα expression in CA1 PSDs. The removal of CaMKII-GluN2B complexes from the PSD during drug withdrawal may serve as a homeostatic mechanism to limit AMPAR-mediated CA1 neuron hyperexcitability and benzodiazepine withdrawal anxiety.
- Direct urine analysis for the identification and quantification of selected benzodiazepines for toxicology screening. [Journal Article]
- J Chromatogr B Analyt Technol Biomed Life Sci 2012 Aug 1.:42-6.
A simple and rapid LC/MS method with direct injection analysis was developed and validated for the identification and quantification of ten benzodiazepines (flunitrazepam, nordiazepam, diazepam, 7-aminoflunitrazepam, flurazepam, bromazepam, midazolam, alprazolam, temazepam and oxazepam) in human urine using diazepam-d5 as internal standard (IS). The main advantage of the proposed methodology is the minimal sample preparation procedure, as diluted urine samples were directly injected into LC/MS system. Electrospray ionization in positive mode using selected ion monitoring was chosen for the identification and quantification of the analytes. The linear range was 50-1000 ng/mL for each analyte, with square correlation coefficient (r(2))≥0.981. Interday and intraday errors were found to be ≤5.72%. The LC/MS method was applied at ten real samples found initially to be positive and negative, using immunoassay technique. Finally the results were confirmed with GC/MS. The method demonstrates simplicity and fast sample preparation, accuracy and specificity of the analytes which make it suitable for replacement of immunoassay screening in urine avoiding thus false negative/false positive results. Using this method, laboratories may overcome the problem of high cost instrumentation such as LC-MS/MS by providing similar sensitivity and specificity with other methods.