Practical Overview of 123I-Ioflupane Imaging in Parkinsonian Syndromes.

Parkinsonian syndromes are a heterogeneous group of progressive neurodegenerative disorders involving the nigrostriatal dopaminergic pathway and are characterized by a wide spectrum of motor and nonmotor symptoms. These syndromes are quite common and can profoundly impact the lives of patients and their families. In addition to classic Parkinson disease, parkinsonian syndromes include multiple additional disorders known collectively as Parkinson-plus syndromes or atypical parkinsonism. These are characterized by the classic parkinsonian motor symptoms with additional distinguishing clinical features. Dopamine transporter SPECT has been developed as a diagnostic tool to assess the levels of dopamine transporters in the striatum. This imaging assessment, which uses iodine 123 (123I) ioflupane, can be useful to differentiate parkinsonian syndromes caused by nigrostriatal degeneration from other clinical mimics such as essential tremor or psychogenic tremor. Dopamine transporter imaging plays a crucial role in diagnosing parkinsonian syndromes, particularly in patients who do not clearly fulfill the clinical criteria for diagnosis. Diagnostic clarification can allow early treatment in appropriate patients and avoid misdiagnosis. At present, only the qualitative interpretation of dopamine transporter SPECT is approved by the U.S. Food and Drug Administration, but quantitative interpretation is often used to supplement qualitative interpretation. The authors provide an overview of patient preparation, common imaging findings, and potential pitfalls that radiologists and nuclear medicine physicians should know when performing and interpreting dopamine transporter examinations. Alternatives to 123I-ioflupane imaging for the evaluation of nigrostriatal degeneration are also briefly discussed. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Intenzo and Colarossi in this issue.

Hyoscyamus albus nortropane alkaloids reduce hyperglycemia and hyperinsulinemia induced in HepG2 cells through the regulation of SIRT1/NF-kB/JNK pathway.

BACKGROUND: Chronic superphysiological glucose and insulin concentrations are known to trigger several tissue and organ failures, including insulin resistance, oxidative stress and chronic low-grade inflammation. Hence, the screening for molecules that may counteract such conditions is essential in current existing therapeutic strategies, thereby the use of medicinal plant derivatives represents a promising axis in this regard. METHODS: In this study, the effect of a selected traditional medicinal plant, Hyoscyamus albus from which, calystegines have been isolated, was investigated in an experimental model of hyperinsulinemia and hyperglycemia induced on HepG2 cells. The mRNA and protein expression levels of different insulin signaling, gluconeogenic and inflammatory pathway- related molecules were examined. Additionally, cell viability and apoptosis, oxidative stress extent and mitochondrial dysfunctions were assayed using flow cytometric and qRT-PCR techniques. RESULTS: Treatment of IR HepG2 cells with calystegines strongly protected the injured cells from apoptosis, oxidative stress and mitochondrial integrity loss. Interestingly, nortropane alkaloids efficiently regulated the impaired glucose metabolism in IR HepG2 cells, through the stimulation of glucose uptake and the modulation of SIRT1/Foxo1/G6PC/mTOR pathway, which is governing the hepatic gluconeogenesis. Furthermore, the alkaloidal extract restored the defective insulin signaling pathway, mainly by promoting the expression of Insr at the mRNA and protein levels. What is more, treated cells exhibited significant mitigated inflammatory response, as evidenced by the modulation and the regulation of the NF- κB/JNK/TLR4 axis and the downstream proinflammatory cytokines recruitment. CONCLUSION: Overall, the present investigation demonstrates that calystegines from Hyoscyamus albus provide cytoprotection to the HepG2 cells against insulin/glucose induced insulin resistance and apoptosis due to the regulation of SIRT1/Foxo1/G6PC/mTOR and NF-κB/JNK/TLR4 signaling pathways. Video Abstract.

Cytotoxic activity induced by the alkaloid extract from Ipomoea carnea on primary murine mixed glial cultures.

The prolonged consumption of Ipomoea carnea produces neurologic symptoms in animals and a typical histological lesion, cytoplasmic vacuolization, especially in neurons. The toxic principles of I. carnea are the alkaloids swainsonine and calystegines B1, B2, B3 and C1. In this study, primary brain cultures from newborn mouse containing mixed glial cells were utilized. These cells were exposed to Ipomoea extracts containing between 0 and 250 µM swainsonine for 48 h. Morphological changes were investigated through Phase Contrast microscopy and Rosenfeld's staining. The extract induced cytoplasmic vacuolization in astrocytes and microglia in a dose dependent manner, being more evident when cultures were exposed to 250 µM of swainsonine. In addition, acridine orange staining evidenced an increase in the number of lysosomes in both microglia and astrocytes cells. Consistent with this, scanning electron microscopy also showed that both types of cells presented morphological characteristics of cell activation. Ultrastructurally, cells showed vacuoles filled with amorphous material and surrounded by a single membrane and also multilayer membranes. Taken together, these findings suggest that swainsonine along with calystegines, are probably responsible for the activation of glial cells due to a possible lysosomal dysfunction and therefore intracellular storage. Our results demonstrate that this in vitro glial cell model is a very good alternative to in vivo studies that require several weeks of animal intoxication to observe similar neurotoxic effects.

Calystegines are Potential Urine Biomarkers for Dietary Exposure to Potato Products.

SCOPE: Metabolites derived from specific foods present in urine samples can provide objective biomarkers of food intake (BFIs). This study investigated the possibility that calystegines (a class of iminosugars) may provide BIFs for potato (Solanum tuberosum L.) product exposure. METHODS AND RESULTS: Calystegine content is examined in published data covering a wide range of potato cultivars. Rapid methods are developed for the quantification of calystegines in cooked potato products and human urine using triple quadrupole mass spectrometry. The potential of calystegines as BFIs for potato consumption is assessed in a controlled food intervention study in the United Kingdom and validated in an epidemiological study in Portugal. Calystegine concentrations are reproducibly above the quantification limit in first morning void urines the day after potato consumption, showing a good dose-response relationship, particularly for calystegine A3 . The design of the controlled intervention mimicks exposure to a typical UK diet and showed that neither differences in preparation/cooking method or influence of other foods in the diet has significant impact on biomarker performance. Calystegine biomarkers also perform well in the independent validation study. CONCLUSION: It is concluded that calystegines have many of the characteristics needed to be considered as specific BFIs for potato product intake.

New fluoroquinolone compounds with endo-nortropine derivatives at C-7 position show antibacterial activity against fluoroquinolone-resistant strains of Staphylococcus aureus.

A series of new fluoroquinolone analogs (3-18) were prepared, in three steps, by substituting chloro esters and esters with cyclic amines on the C-7 endo-nortropine derivatives of difluoroquinolone acid. All the synthesized compounds displayed good MIC against the Staphylococcus aureus when initially screened for Escherichia coli, S. aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa. The molecules were further evaluated for their antibacterial activity against fluoroquinolone-resistant strains of S. aureus and for cytotoxic assay. Based on the results, five of the sixteen compounds displayed the potential to be developed further for treatment against fluoroquinolone-resistant strains of S. aureus.

Transcutaneous posterior tibial nerve electrostimulation with low dose trospium chloride: Could it be used as a second line treatment of overactive bladder in females.

AIM: To evaluate the effect of adding low dose trospium chloride with transcutaneous posterior tibial nerve stimulation (TPTNS) in the treatment of overactive bladder (OAB) in females after failure of behavioral therapy. METHODS: We randomized 30 women with OAB, in two groups: G I received 30 min TPTNS, three times a week; GII received TPTNS plus 20 mg trospium chloride daily. OAB Symptom Score questionnaire (OABSS), Incontinence Impact Questionnaire-short form 7 (IIQ-7), 3 day voiding diary and urodynamics at weeks 0 and 8 were evaluated. RESULTS: The groups were similar before treatment. Eight weeks after treatment, the mean OABSS decreased significantly to 8.53 ± 1.30 for group II vs 10.0 ± 2.0 for GI (P < 0.024). The mean IIQ-7 score decreased significantly to 51.86 ± 17.26 in group I vs 31.99 ± 9.26 in group II (P < 0.001). Before treatment, 11 (73.3%) and 4 (26.7%) patients in each group had moderate and poor quality of life (QoL), respectively. After treatment, 6 (40%) and 14 (93.3%) had good QoL, 7 (46.7%) and 1 (6.7%) had moderate QoL in GI and GII, respectively. Two (13.3%) patients in GI had poor QoL. The mean frequency was reduced to 8.60 ± 0.83 vs 10.60 ± 2.32 for GII and GI respectively (P = 0.006). The cystometric capacity increased from 263.40 ± 50.45 to 377.80 ± 112.92 mL (P = 0.001) for GII vs 250.13 ± 56.24 to 296.40 ± 99.0 mL (P = 0.026) for GI. CONCLUSION: TPTNS combined with low dose trospium chloride proved to be more effective than TPTNS alone in the treatment of OAB in females.

Use of 11C-PE2I PET in differential diagnosis of parkinsonian disorders.

UNLABELLED: In idiopathic Parkinson disease and atypical parkinsonian disorders, central dopaminergic and overall brain functional activity are altered to different degrees, causing difficulties in achieving an unambiguous clinical diagnosis. A dual examination using (123)I-FP-CIT ((123)I-N-ω-fluoropropyl-2ß-carbomethoxy-3ß-(4-iodophenyl)nortropane, or (123)I-ioflupane) SPECT and(18)F-FDG PET provides complementary information on dopamine transporter (DAT) availability and overall brain functional activity, respectively. Parametric images based on a single, dynamic (11)C-PE2I (N-(3-iodoprop-2E-enyl)-2ß-carbomethoxy-3ß-(4-methyl-phenyl)nortropane) scan potentially supply both DAT availability (nondisplaceable binding potential [BPND]) and relative cerebral blood flow (relative delivery [R1]) at voxel level. This study aimed to evaluate the validity of (11)C-PE2I PET against the dual-modality approach using (123)I-FP-CIT SPECT and (18)F-FDG PET. METHODS: Sixteen patients with parkinsonian disorders had a dual examination with (18)F-FDG PET and (123)I-FP-CIT SPECT following clinical routines and additionally an experimental (11)C-PE2I PET scan. Parametric BPND and R1 images were generated using receptor parametric mapping with the cerebellum as a reference. T1-weighted MR imaging was used for automated definition of volumes of interest (VOI). The DAT VOIs included the basal ganglia, whereas the overall brain functional activity was examined using VOIs across the brain. BPND and R1 values were compared with normalized (123)I-FP-CIT and (18)F-FDG uptake values, respectively, using Pearson correlations and regression analyses. In addition, 2 masked interpreters evaluated the images visually, in both the routine and the experimental datasets, for comparison of patient diagnoses. RESULTS: Parametric (11)C-PE2I BPND and R1 images showed high consistency with (123)I-FP-CIT SPECT and (18)F-FDG PET images. Correlations between (11)C-PE2I BPND and (123)I-FP-CIT uptake ratios were 0.97 and 0.76 in the putamen and caudate nucleus, respectively. Regional (11)C-PE2I R1 values were moderately to highly correlated with normalized (18)F-FDG values (range, 0.61-0.94). Visual assessment of DAT availability showed a high consistency between (11)C-PE2I BPND and (123)I-FP-CIT images, whereas the consistency was somewhat lower for appraisal of overall brain functional activity using (123)I-FP-CIT and (18)F-FDG images. Substantial differences were found between clinical diagnosis and both neuroimaging diagnoses. CONCLUSION: A single, dynamic (11)C-PE2I PET investigation is a powerful alternative to a dual examination with (123)I-FP-CIT SPECT and (18)F-FDG PET for differential diagnosis of parkinsonian disorders. A large-scale patient study is, however, needed to further investigate distinct pathologic patterns in overall brain functional activity for various parkinsonian disorders.

The cost-effectiveness of solifenacin vs. trospium in the treatment of patients with overactive bladder in the German National Health Service.

OBJECTIVE: To carry out a cost-utility analysis comparing initial treatment of patients with overactive bladder (OAB) with solifenacin 5 mg/day versus either trospium 20 mg twice a day or trospium 60 mg/day from the perspective of the German National Health Service. METHODS: A decision analytic model with a 3 month cycle was developed to follow a cohort of OAB patients treated with either solifenacin or trospium during a 1 year period. Costs and utilities were accumulated as patients transitioned through the four cycles in the model. Some of the solifenacin patients were titrated from 5 mg to 10 mg/day at 3 months. Utility values were obtained from the published literature and pad use was based on a US resource utilization study. Adherence rates for individual treatments were derived from a United Kingdom general practitioner database review. The change in the mean number of urgency urinary incontinence episodes/day from after 12 weeks was the main outcome measure. Baseline effectiveness values for solifenacin and trospium were calculated using the Poisson distribution. Patients who failed second-line therapy were referred to a specialist visit. Results were expressed in terms of incremental cost-utility ratios. RESULTS: Total annual costs for solifenacin, trospium 20 mg and trospium 60 mg were €970.01, €860.05 and €875.05 respectively. Drug use represented 43%, 28% and 29% of total costs and pad use varied between 45% and 57%. Differences between cumulative utilities were small but favored solifenacin (0.6857 vs. 0.6802 to 0.6800). The baseline incremental cost-effectiveness ratio ranged from €16,657 to €19,893 per QALY. LIMITATIONS: The difference in cumulative utility favoring solifenacin was small (0.0055-0.0057 QALYs). A small absolute change in the cumulative utilities can have a marked impact on the overall incremental cost-effectiveness ratios (ICERs) and care should be taken when interpreting the results. CONCLUSION: Solifenacin would appear to be cost-effective with an ICER of no more than €20,000/QALY. However, small differences in utility between the alternatives means that the results are sensitive to adjustments in the values of the assigned utilities, effectiveness and discontinuation rates.

Glycoalkaloid and calystegine levels in table potato cultivars subjected to wounding, light, and heat treatments.

Potato tubers naturally contain a number of defense substances, some of which are of major concern for food safety. Among these substances are the glycoalkaloids and calystegines. We have here analyzed levels of glycoalkaloids (α-chaconine and α-solanine) and calystegines (A3, B2, and B4) in potato tubers subjected to mechanical wounding, light exposure, or elevated temperature: stress treatments that are known or anticipated to induce glycoalkaloid levels. Basal glycoalkaloid levels in tubers varied between potato cultivars. Wounding and light exposure, but not heat, increased tuber glycoalkaloid levels, and the relative response differed among the cultivars. Also, calystegine levels varied between cultivars, with calystegine B4 showing the most marked variation. However, the total calystegine level was not affected by wounding or light exposure. The results demonstrate a strong variation among potato cultivars with regard to postharvest glycoalkaloid increases, and they suggest that the biosynthesis of glycoalkaloids and calystegines occurs independently of each other.

A concise stereoselective synthesis of (-)-erycibelline.

(-)-Erycibelline, the dihydroxynortropane alkaloid isolated from Erycibe elliptilimba Merr. et Chun., was synthesized using a cyclic nitrone as advanced intermediate, wherein the key step was the SmI(2)-induced intramolecular reductive coupling of cyclic nitrone with aldehyde which resulted in good yield and stereoselectivity.

Comparison of different treatment protocols in the treatment of idiopathic detrusor overactivity: a randomized controlled trial.

OBJECTIVE: To investigate and compare the effectiveness of various treatment protocols for the treatment of women with idiopathic detrusor overactivity. DESIGN: Prospective, randomized controlled trial. SETTING: Departments of Physiotherapy and Rehabilitation and Obstetrics and Gynaecology, Hacettepe University. SUBJECTS: Forty-six subjects were randomized to three groups. INTERVENTIONS: The first group received only pharmacotherapy, the second group received only physiotherapy and in the third group pharmacotherapy was combined with physiotherapy (combined therapy group). MAIN MEASURES: All patients were evaluated at the beginning and at the end of treatment. Assessment parameters were maximum cystometric capacity, electromyographic activity of pelvic floor muscles, voiding diary parameters, the amount of urine leakage and the quality of life score. RESULTS: The maximum cystometric capacity and the electromyographic activity of pelvic floor muscles increased significantly and the number of voids/day and incontinence episodes/day, and the amount of urine leakage reduced significantly (P < 0.05) in both physiotherapy and combined therapy groups while there was no significant difference in the pharmacotherapy group. After treatment, the number of voids/day increased by 0.3 ± 3.4 in the pharmacotherapy group (P > 0.05) and decreased by 5.1 ± 5.5 and 4.7 ± 5.6 in the physiotherapy and combined therapy groups, respectively (P < 0.05). Statistically significant improvements were observed in all groups according to the number of voids/night and the quality of life scores at the end of the treatment. CONCLUSION: The physiotherapy protocol we introduced in the present study with or without anticholinergic therapy has a substantial positive impact on the treatment of female patients with idiopathic detrusor overactivity.

Comparison of intravaginal electrical stimulation and trospium hydrochloride in women with overactive bladder syndrome: a randomized controlled study.

OBJECTIVE: To compare the effects of trospium hydrochloride and electrical stimulation on urodynamic parameters, bladder diary, quality of life and psychological symptoms in female patients with overactive bladder syndrome. DESIGN: Prospective, randomized controlled trial. SETTING: Department of Physical Medicine and Rehabilitation, University Hospital. SUBJECTS: Thirty-five patients were divided into either trospium chloride (Group 1) or intravaginal electrical stimulation therapy (Group 2). MAIN OUTCOME MEASURES: All patients were assessed at the beginning of the treatment, at weeks 6 (end of treatment), 10 and 18 according to urodynamic parameters, voiding diary parameters, severity of urgency (visual analogue scale, VAS), the Incontinence Impact Questionnaire Short Form (IIQ-7), and the Beck Depression Inventory. RESULTS: Statistically significant improvements were observed in both groups according to some urodynamic parameters, voiding diary parameters, VAS urgency severity, Incontinence Impact Questionnaire Short Form and Beck Depression Inventory scores at the end of the treatment (P<0.05). During the 18-week follow-up period, deteriorations were observed in many parameters in both groups although improvements in the frequency of urgency, the frequency of incontinence episodes, VAS urgency severity, and Beck Depression Inventory score in Group 2 persisted (P<0.05). Significant differences were not detected between groups at the end of the treatment or during the posttreatment follow-up controls (P>0.05). CONCLUSION: No difference was detected between trospium hydrochloride and intravaginal electrical stimulation in the treatment of female overactive bladder syndrome. Discontinuation of both treatments caused deterioration in most of the objective and subjective symptoms of overactive bladder syndrome.

Increase in thalamic binding of [(11)C]PE2I in patients with schizophrenia: a positron emission tomography study of dopamine transporter.

Previous in vivo imaging studies reported no difference in dopamine transporter (DAT) bindings in the striatum between control subjects and patients with schizophrenia. However, as the signals of radioligands with moderate affinity were insufficient for allowing the evaluation of small amounts of DAT, DAT binding in extrastriatal regions has not been determined. Positron emission tomography scanning using [(11)C]PE2I was performed on eight patients with schizophrenia and twelve normal control subjects. Binding potential (BP(ND)) for DAT in the caudate, putamen, thalamus and substantia nigra was calculated, using the cerebellum as reference region. In patients with schizophrenia, clinical symptoms were evaluated by Positive and Negative Syndrome Scale (PANSS). BP(ND) in the thalamus of patients with schizophrenia was significantly higher than in control subjects (P=0.044). In patients with schizophrenia, there were significantly positive correlations between BP(ND) in the thalamus and total (r=0.75), positive (r=0.78) and negative PANSS scores (r=0.82). Altered DAT in the thalamus might be related to the pathophysiology and clinical symptoms of schizophrenia.

Electrophoretic determination of calystegines A3 and B2 in potato.

Potatoes, members of the Solanaceae plant family, contain calystegines, water-soluble nortropane alkaloids, which are biologically active as glycosidase inhibitors. The content of calystegines A(3) and B(2) in different varieties of potato and in various parts of the tubers (whole potato, peel, flesh, and sprouts) were analysed by new capillary zone electrophoresis and capillary isotachophoresis methods and by the routine GC method. The optimized background electrolyte for capillary zone electrophoretic analysis was mixture of 20 mM histidine, 20 mM N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid and 20% (v/v) methanol in demineralized water. Calystegines were detected by indirect UV detection at 210 nm. A clear separation of calystegines from other components of the methanolic sample extract was achieved within 4 min. The electrolytes for isotachophoretic analysis consisted of 5 mM NH(4)OH, 10 mM N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, 0.1% hydroxyethylcellulose and 20% (v/v) methanol in demineralized water (leading) and 5 mM histidine+10 mM acetic acid+20% (v/v) methanol in demineralized water (terminating). Calystegines were separated within 20 min and detected by a conductimeter. Method characteristics of both zone electrophoresis and isotachophoresis, i.e., linearity (10-100 ng/microl and 1-10 ng/microl), accuracy (recovery 96+/-5% and 98+/-4%), intra-assay repeatability (4.2% and 3.5%), and detection limit (3 and 0.4 ng/microl) were evaluated. Simple sample preparation, sufficient sensitivity, speed of analysis, and low running cost are important attributes of the electrophoretic methods. The overall results of electrophoretic methods were comparable with GC.

[24-h dynamics of urination in patients with overactive urinary bladder].

Home 3-day uroflowmetry was made in 41 female patients (mean age 46 years) before and after therapy for overactive bladder (OB). The course of therapy lasting from 6 weeks to 3 months included M-cholinolytics and vascular medication. Estimation of the bladder capacity in different time of 24-h period revealed circadian deviations of urinary flow and volumes. Administration of short-term M-cholinolytics enables chronotherapy providing maximal effects within 4-6 hours, possibility to vary doses. In view of this, optimal cholinergic therapy of OB is trospium chloride which has necessary properties, high safety and wide dose range.

Comparison of the efficacy and tolerability of solifenacin succinate with or without previous use of trospium chloride.

Overactive bladder syndrome (OBS) is described as urinary urgency with or without incontinence, usually with increased daytime frequency and nocturia in the absence of another identifiable pathological process. Nowadays and despite other alternative therapies, the mainstay of OBS is still the pharmacological approach, mainly with anti-muscarinic drugs. To compare the efficacy of a 30-day solifenacin succinate (5 mg OD) treatment with or without previous medication with trospium chloride, a prostective open, two-arm, parallel group study was conducted for 5 weeks in 40 patients with OBS. The primary endpoint was patient self-assessment of improvement after 30 days of medication. Secondary endpoints included the reduction of the daily number of voids and urgency or involuntary leakage episodes. Adverse reactions and therapeutic stoppage were also evaluated. To be included in the trospium chloride treatment group, patients were required to have been treated with such drug for 1 to 6 months before the present study. Evaluation and efficacy assessment were accomplished using a 3-day bladder diary and an urgency severity scale (USS). Safety assessment was done by recording all the patients' complaints after starting medication. A total of 40 patients were enrolled for this study, 19 without previous medication and 21 who had already tried trospium chloride. Two patients from the non-previous medication group were excluded. Globally, there was a statistically significant reduction for the USS (2.73-->1.73), the daily number of voids (9.5-->7.0), of urgency episodes (9.1-->4.0) and of involuntary leakage episodes (3.6-->1.0) over the 24 h. Six patients had no improvement, four from the previous trospium chloride group and two from the non-previous medication group. Three patients reported side effects, two cases of dry mouth and one case of constipation. One patient dropped out of the treatment due to an unspecified intolerance. Solifenacin succinate 5 mg seems to be effective concerning patients' self-assessment of improvement and decrease in the mean number of daily voids, urgency episodes and incontinence episodes. This was reported both in patients who have already been medicated with trospium chloride and those who have never taken any kind of medication. Regarding side effects, solifenacin is quite well-tolerated in both groups.

[11C]LBT-999: a suitable radioligand for investigation of extra-striatal dopamine transporter with PET.

A new tropane derivative, (E)-N-(4-fluorobut-2-enyl)-2beta-carbomethoxy-3beta-(4'-tolyl)nortropane (LBT-999), was evaluated in baboons as a carbon-11 radioligand for studies of the dopamine transporter (DAT) using positron emission tomography (PET). Brain uptake was high in the striatum (17 and 13% ID/100 mL tissue in the putamen and the caudate, respectively), moderate in the midbrain and thalamus (5 and 3% ID/100 mL tissue, respectively), and low in the cortex and cerebellum (2% ID/100 mL tissue) at 30 min post injection. The striatum-to-cerebellum ratio was high (30 at 110 min post injection). Specific binding was completely blocked following pretreatment with the DAT antagonists GBR12909 (5 mg/kg i.v.) or PE2I (1 mg/kg i.v.). The [(11)C]LBT-999 uptake was decreased by these antagonists in the putamen (-79 and -92%, respectively), caudate (-80 and -91%, respectively), midbrain (-73 and -78%, respectively), and thalamus (-34 and -46%, respectively). The serotonin transporter (SERT) antagonist citalopram (5 mg/kg i.v.) or the norepinephrine transporter antagonist maprotiline (5 mg/kg i.v.) had no effect on LBT specific binding. Pharmacological challenge with PE2I (1 mg/kg i.v.) induced a rapid and almost complete decrease of the specific binding in the putamen (-97%), caudate (-96%), midbrain (-96%), and thalamus (-81%), confirming the reversibility of [(11)C]LBT-999 binding. The high brain uptake of [(11)C]LBT-999 together with its low nonspecific binding (reflected by the very high brain structure-to-cerebellum ratio) indicate that this radiotracer is an excellent candidate for in vivo quantification of the DAT, especially in extrastriatal structures, such as the midbrain.

Predictive power of an in vitro system to assess drug interactions of an antimuscarinic medication: a comparison of in vitro and in vivo drug-drug interaction studies of trospium chloride with digoxin.

The authors studied a potential drug-drug interaction via findings from in vitro and in vivo studies, to assess whether the in vitro system was predictive of in vivo clinical pharmacokinetic outcomes. An in vitro experiment and a clinical study were performed to assess the potential for interaction. The effect of trospium chloride on human P-glycoprotein-mediated transport of [3H]-digoxin was determined in vitro. A randomized, crossover clinical trial in 40 subjects was performed to evaluate the effect of trospium on the pharmacokinetics of digoxin in vivo. The findings from the studies were then compared. The in vitro findings in this study were corroborated by the clinical study via assessment of inhibition and impact on pharmacokinetic parameters. The in vitro system for assessment of a potential interaction of 2 drugs excreted primarily through the kidney was predictive of the pharmacokinetic outcomes obtained from a clinical setting.

Putrescine N-methyltransferase in Solanum tuberosum L., a calystegine-forming plant.

Putrescine N-methyltransferase (PMT, EC 2.1.1.53) catalyses the first specific step in the biosynthesis of tropane and nicotine alkaloids. Potato (Solanum tuberosum L.) contains neither nicotine nor the medicinal tropane alkaloids hyoscyamine or scopolamine, but calystegines. They are nortropane alkaloids with glycosidase inhibitory activity. Based on the assumption of calystegine formation by the tropane alkaloid pathway, PMT genes and enzymes were investigated in potato. Sprouting tubers contained both N-methylputrescine and PMT activity. Two cDNA clones coding for PMTs were obtained together with a cDNA clone for spermidine synthase (SPDS, EC 2.5.1.16). The pmt sequences resemble those from Nicotiana tabacum (85% identity) and those from tropane alkaloid plants, Atropa belladonna (80% identity) and Hyoscyamus niger (79% identity). They are less similar to SPDS of S. tuberosum (66% identity). Expression of pmt1 and spds cDNA in Escherichia coli yielded active enzymes, while pmt2 expression resulted in insoluble protein. Chimera proteins obtained by fusion of fragments of S. tuberosum pmt2 and H. niger pmt were active as PMT, if the initial part of pmt2 was used, indicating that a mutation in the terminal part of the gene caused insolubility of the enzyme. PMT1 was purified after expression in E. coli and proved to be an active N-methyltransferase without SPDS activity. The enzyme was specific for putrescine (K (M) 250 microM) and inhibited by n-butylamine and cadaverine. While spds was transcribed in all plant organs, pmt transcripts were found in small tuber sprouts only. The results confirm that in potato genes and enzymes specific for the tropane alkaloid metabolism are expressed and active.

Antimuscarinic agents exhibit local inhibitory effects on muscarinic receptors in bladder-afferent pathways.

OBJECTIVES: To investigate the potential of antimuscarinic agents for sensory mechanisms in overactive bladder using intravesical instillation. METHODS: Antimuscarinic agents were instilled intravesically in rats using two protocols. In the high-dose protocol, 5 mg atropine, oxybutynin, and dimethindene (M2-selective muscarinic receptor antagonist) were instilled into the bladder, and cystometric parameters, such as bladder capacity, intercontraction interval, pressure threshold, and maximal voiding pressure were monitored. In the low-dose protocol, 0.1 and 0.5 mug/mL oxybutynin, trospium, tolterodine, and dimethindene were continuously infused into the bladder. The doses chosen were based on the calculated urine-excreted concentrations of trospium typically achieved from human oral treatment of 40 mg/day. The effect of carbachol with and without the low-dose agents was then assessed. RESULTS: With the high-dose protocol, bladder capacity, intercontraction interval, and pressure threshold were increased when atropine and oxybutynin were instilled, but not when dimethindene was used. The maximal voiding pressure was not affected by any of the agents tested. In the low-dose protocol, none of the cystometric parameters were altered with antimuscarinic agents alone. The intercontraction interval decreased with intravesical carbachol (65% +/- 0.1% compared with baseline), but this was prevented with concomitant antimuscarinic agents. CONCLUSIONS: We have separated the local inhibitory effects of antimuscarinic agents during the storage phase from a decrease in voiding pressure. Intravesical instillation of antimuscarinic agents at clinically meaningful concentrations also suppressed carbachol-induced bladder overactivity. Antimuscarinic agents may be effective in treating overactive bladder, not only by suppression of muscarinic receptor-mediated detrusor muscle contractions, but also by blocking muscarinic receptors in bladder-afferent pathways.