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Background: [ 18 F]FEPPA is a potent TSPO imaging agent that has been found to be a potential tracer for imaging neuroinflammation. In order to fulfill the demand of this tracer for preclinical and clinical studies, we have developed a one-pot automated synthesis with simplified HPLC purification of this tracer, which was then used for PET imaging of neuroinflammation in fine particulate matter- (PM2.5-) exposed rats., Results: Using this automated synthesis method, the RCY of the [ 18 F]FEPPA was 38 ± 4% ( n = 17, EOB) in a synthesis time of 83 ± 8 min from EOB. The radiochemical purity and molar activities were greater than 99% and 209 ± 138 GBq/ μ mol (EOS, n = 15), respectively. The quality of the [ 18 F]FEPPA synthesized by this method met the U.S. Pharmacopoeia (USP) criteria. The stability test showed that the [ 18 F]FEPPA was stable at 21 ± 2°C for up to 4 hr after the end of synthesis (EOS). Moreover, microPET imaging showed that increased tracer activity of [ 18 F]FEPPA in the brain of PM2.5-exposed rats ( n = 6) were higher than that of normal controls ( n = 6) and regional-specific., Conclusions: Using the improved semipreparative HPLC purification, [ 18 F]FEPPA has been produced in high quantity, high quality, and high reproducibility and, for the first time, used for PET imaging the effects of PM2.5 in the rat brain. It is ready to be used for imaging inflammation in various clinical or preclinical studies, especially for nearby PET centers without cyclotrons., Competing Interests: The authors declare that they have no competing interests., (Copyright © 2022 Mei-Fang Cheng et al.)

Background: Leucine-rich repeat kinase 2 (LRRK2) is a common risk gene for Parkinson's disease (PD) and inflammatory bowel disorders. However, the penetrance of the most prevalent LRRK2 mutation, G2019S, is <50%. Factors other than genetic mutations are needed in PD process., Objectives: To examine whether and how gut inflammation may act as an environmental trigger to neurodegeneration in PD., Methods: A mild and chronic dextran sodium sulfate (DSS)-induced colitis mice model harboring LRRK2 G2019S mutation was established. The colitis severity, immune responses, locomotor function, dopaminergic neuron, and microglia integrity were compared between littermate controls, transgenic LRRK2 wild type (WT), and LRRK2 G2019S mice., Results: The LRRK2 G2019S mice are more vulnerable to DSS-induced colitis than littermate controls or LRRK2 WT animals with increased intestinal expressions of pattern-recognition receptors, including toll-like receptors (TLRs), nuclear factor (NF)-κB activation, and pro-inflammatory cytokines secretion, especially tumor necrosis factor (TNF)-α. Notably, the colonic expression of α-synuclein was significantly increased in LRRK2 G2019S colitis mice. We subsequently observed more aggravated locomotor defect, microglia activation, and dopaminergic neuron loss in LRRK2 G2019S colitis mice than control animals. Treatment with anti-TNF-α monoclonal antibody, adalimumab, abrogated both gut and neuroinflammation, mitigated neurodegeneration, and improved locomotor function in LRRK2 G2019S colitis mice. Finally, we validated increased colonic expressions of LRRK2, TLRs, and NF-κB pathway proteins and elevated plasma TNF-α level in PD patients compared to controls, especially in those with LRRK2 risk variants., Conclusions: Our findings demonstrate that chronic colitis promotes parkinsonism in genetically susceptible mice and TNF-α plays a detrimental role in the gut-brain axis of PD. © 2021 International Parkinson and Movement Disorder Society., (© 2021 International Parkinson and Movement Disorder Society.)

Bezafibrate, a pan-peroxisome proliferator-activated receptor (PPAR) agonist, reportedly attenuated tau pathology in a transgenic mouse model of primary tauopathy. Since tau pathology is a neuropathological hallmark of Alzheimer's disease (AD), bezafibrate may be a potential drug for the treatment of AD. However, no study has investigated its effects in AD models. Thus, we aimed to evaluate whether bezafibrate has neuroprotective effects in a sporadic AD model induced by streptozotocin (STZ) intracerebroventricular (ICV) injection. Rats were administered STZ-ICV (3 mg/kg) followed by bezafibrate (50 mg/kg/day, intraperitoneal) for 4 weeks. Behavior tests and positron emission tomography (PET) were performed to evaluate longitudinal changes in cognitive function, tau pathology, and cerebral glucose metabolism. Immunofluorescence staining was performed to assess neuronal survival and microglial accumulation. STZ-ICV administration induced significant cognitive impairment and substantial neuronal loss, tau pathology, glucose hypometabolism, and microgliosis in the cortex and hippocampus, while bezafibrate effectively attenuated these abnormalities. This study demonstrated that bezafibrate has long-lasting neuroprotective effects in a sporadic AD model. Our data indicate that the neuroprotective effects of bezafibrate might be associated with its ability to ameliorate tau pathology, brain glucose hypometabolism, and neuroinflammation. These findings suggest that bezafibrate is a potential multi-target drug candidate for the treatment of AD.

Background: Expression of translocator protein (TSPO) on the outer mitochondrial membrane of activated microglia is strongly associated with neuroinflammation. The second-generation PET ligand [ 18 F]FEPPA specifically binds TSPO to enable in vivo visualization and quantification of neuroinflammation. We optimized a fully automated radiosynthesis method and evaluated the utility of [ 18 F]FEPPA, the second-generation PET ligand specifically binds TSPO, in a mouse model of systemic LPS challenge to detect TSPO-associated signals of central and peripheral inflammation. In vivo dynamic PET/MR imaging was performed in LPS-induced and control mice after [ 18 F]FEPPA administration. The relationship between the [ 18 F]FEPPA signal and the dose of LPS was assessed. The cytokine levels (i.e., TNF-α, Il-1β, Il-6) in LPS-induced mice were measured by RT-PCR. Standard uptake value (SUV), total volume of distribution (VT) and area under the curve (AUC) were determined based on the metabolite-uncorrected plasma input function. Western blotting and immunostaining were used to measure TSPO expression in the brain., Results: The fully automated [ 18 F]FEPPA radiosynthesis produced an uncorrected radiochemical yield of 30 ± 2% within 80 min, with a radiochemical purity greater than 99% and specific activity of 148.9‒216.8 GBq/µmol. Significant differences were observed in the brain after [ 18 F]FEPPA administration: SUV, VT and AUC were 1.61 ± 0.1, 1.25 ± 0.12 and 1.58 ± 0.09-fold higher in LPS-injected mice than controls. TNF-α, Il-1β and Il-6 mRNA levels were also elevated in the brains of LPS-injected mice. Western blotting revealed TSPO (p < 0.05) and Iba-1 (p < 0.01) were upregulated in the brain after LPS administration. In LPS-injected mice, TSPO immunoactivity colocalized with Iba-1 in the cerebrum and TSPO was significantly overexpressed in the hippocampus and cerebellum. The peripheral organs (heart, lung) of LPS-injected mice had higher [ 18 F]FEPPA signal-to-noise ratios than control mice., Conclusions: Based on the current data on ligand specificity and selectivity in central tissues using 7 T PET/MR imaging, we demonstrate that [ 18 F]FEPPA accumulations significant increased in the specific brain regions of systemic LPS-induced neuroinflammation (5 mg/kg). Future investigations are needed to determine the sensitivity of [ 18 F]FEPPA as a biomarker of neuroinflammation as well as the correlation between the PET signal intensity and the expression levels of TSPO.

(4S)-4-(3-[18F]Fluoropropyl)-L-glutamic acid ([18F]FSPG) is a positron emission tomography (PET) imaging agent for measuring the system xC- transporter activity. It has been used for the detection of various cancers and metastasis in clinical trials. [18F]FSPG is also a promising diagnostic tool for evaluation of multiple sclerosis, drug resistance in chemotherapy, inflammatory brain diseases, and infectious lesions. Due to the very short half-life (110 min) of 18F nuclide, [18F]FSPG needs to be produced on a daily basis; therefore, fast and efficient synthesis and analytical methods for quality control must be established to assure the quality and safety of [18F]FSPG for clinical use. To manufacture cGMP-compliant [18F]FSPG, all four nonradioactive stereoisomers of FSPG were prepared as reference standards for analysis. (2S,4S)-1 and (2R,4R)-1 were synthesized starting from protected L- and D-glutamate derivatives in three steps, whereas (2S,4R)-1 and (2R,4S)-1 were prepared in three steps from protected (S)- and (R)-pyroglutamates. A chiral HPLC method for simultaneous determination of four FSPG stereoisomers was developed by using a 3-cm Chirex 3126 column and a MeCN/CuSO4(aq) mobile phase. In this method, (2R,4S)-1, (2S,4S)-1, (2R,4R)-1, and (2S,4R)-1 were eluted in sequence with sufficient resolution in less than 25 min without derivatization. Scale-up synthesis of intermediates for the production of [18F]FSPG in high optical purity was achieved via stereo-selective synthesis or resolution by recrystallization. The enantiomeric excess of intermediates was determined by HPLC using a Chiralcel OD column and monitored at 220 nm. The nonradioactive precursor with >98% ee can be readily distributed to other facilities for the production of [18F]FSPG. Based on the above accomplishments, cGMP-compliant [18F]FSPG met the acceptance criteria in specifications and was successfully manufactured for human use. It has been routinely prepared and used in several pancreatic ductal adenocarcinoma metastasis-related clinical trials., Competing Interests: The authors have declared that no competing interests exist.

A series of diphenylsulfide derivatives with various substitutions at the 4-position on phenyl ring A and different lengths of the 2-fluoroethoxy-substituted side-chain at the 4'-position on ring B were synthesized and evaluated as potential positron emission tomography (PET) imaging agents for serotonin transporters (SERT). These ligands exhibited high SERT binding affinities (K i  = 0.11-1.3 nM) and the 4-methyl-substituted (4-Me) compounds 7a and 8a displayed excellent selectivity for SERT versus norepinephrine transporters (NET) (392- and 700-fold, respectively). In the parallel artificial membrane permeability assay (PAMPA), these ligands demonstrated moderate to high brain penetration, and the 4-Me analogs showed higher BBB permeability than the corresponding 4-F analogs. The 2-fluoroethoxy-substituted ligands showed higher metabolic stability and lower lipophilicity than 4-F-ADAM. [ 18 F]7a-c were readily prepared using an automatic synthesizer and exhibited significant uptake and slow washout in rat brains. At 120 min after iv injection, [ 18 F]7a exhibited the highest uptake in the midbrain, whereas [ 18 F]7b exhibited the highest uptake in the hypothalamus and midbrain. After treatment with citalopram, a SERT-selective ligand, the uptake of [ 18 F]7a in the hypothalamus and striatum was significantly decreased. The potent and highly selective SERT binding and the selective and reversible accumulation in SERT-rich brain regions suggested that [ 18 F]7a is a promising lead for the further development of novel [ 18 F]-labeled PET imaging agents for SERT binding sites in the brain., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: Epigenetic dysfunction is implicated in many neurologic, psychiatric and oncologic diseases. Consequently, histone deacetylases (HDACs) inhibitors have been developed as therapeutic and imaging agents for these diseases. However, only a few radiotracers have been developed as HDACs imaging agents for the central nervous system (CNS). We report herein the synthesis and evaluation of [ 18 F]INER-1577-3 ([ 18 F]5) as an HDACs imaging agent for CNS., Methods: [ 18 F]INER-1577-3 ([ 18 F]5) was synthesized by two methods: one-step (A) and two-step (B) methods. Briefly, radiofluorination of the corresponding precursors (11, 12) with K[ 18 F]/K2.2.2 followed by purifications with HPLC gave ([ 18 F]5). The quality of [ 18 F]INER- 1577-3 synthesized by these methods was verified by HPLC and TLC as compared to an authentic sample. The inhibitions of [ 18 F]INER-1577-3 and related HDACs inhibitors on tumor cells growth were carried out with breast cancer cell line 4T1 and MCF-7. The whole-body and brain uptake of [ 18 F]INER-1577-3 in rats and AD mice were determined using a micro-PET scanner and the data was analyzed using PMOD., Results: The radiochemical yield of [ 18 F]INER-1577-3 synthesized by these two methods was 1.4 % (Method A) and 8.8% (Method B) (EOB), respectively. The synthesis time was 115 min and 100 min, respectively, from EOB. The inhibition studies showed that INER-1577-3 has a significant inhibitory effect in HDAC6 and HDAC8 but not HDAC2. PET studies in rats and AD mice showed a maximum at about 15 min postinjection for the whole brain of a rat (0.47 ± 0.03 %ID/g), SAMP8 mice (5.63 ± 1.09 %ID/g) and SAMR1 mice (7.23 ± 1.21 %ID/g)., Conclusion: This study showed that INER-1577-3 can inhibit tumor cell growth and is one of a few HDACs inhibitors that can penetrate the blood-brain barrier (BBB) and monitor HDAC activities in AD mice. Thus, [ 18 F]INER-1577-3 may be a potent HDACs imaging agent, especially for CNS., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Intra-striatal transplantation of fetal ventral mesencephalic (VM) tissue has a therapeutic effect on patients with Parkinson's disease (PD). Sertoli cells (SCs) possess immune-modulatory properties that benefit transplantation. We hypothesized that co-graft of SCs with VM tissue can attenuate rejection. Hemi-parkinsonian rats were generated by injecting 6-hydroxydopamine into the right medial forebrain bundle of Sprague Dawley (SD) rats. The rats were then intrastriatally transplanted with VM tissue from rats or pigs (rVM or pVM), with/without a co-graft of SCs (rVM+SCs or pVM+SCs). Recovery of dopaminergic function and survival of the grafts were evaluated using the apomorphine-induced rotation test and small animal-positron emission tomography (PET) coupled with [ 18 F] DOPA or [ 18 F] FE-PE2I, respectively. Immunohistochemistry (IHC) examination was used to determine the survival of the grafted dopaminergic neurons in the striatum and to investigate immune-modulatory effects of SCs. The results showed that the rVM+SCs and pVM+SCs groups had significantly improved drug-induced rotational behavior compared with the VM alone groups. PET revealed a significant increase in specific uptake ratios (SURs) of [ 18 F] DOPA and [ 18 F] FE-PE2I in the grafted striatum of the rVM+SCs and pVM+SCs groups as compared to that of the rVM and pVM groups. SC and VM tissue co-graft led to better dopaminergic (DA) cell survival. The co-grafted groups exhibited lower populations of T-cells and activated microglia compared to the groups without SCs. Our results suggest that co-graft of SCs benefit both xeno- and allo-transplantation of VM tissue in a PD rat model. Use of SCs enhanced the survival of the grafted dopaminergic neurons and improved functional recovery. The enhancement may in part be attributable to the immune-modulatory properties of SCs. In addition, [ 18 F]DOPA and [ 18 F]FE-PE2I coupled with PET may provide a feasible method for in vivo evaluation of the functional integrity of the grafted DA cell in parkinsonian rats.

This study investigated the effect of dextromethorphan (DXM) against Parkinson's disease (PD) in rats and explored the association between DXM dose and PD risk in elderly patients 65 years and older using a population-based database. The PD rat model (Sprague Dawley rats) was induced by injecting 6-hydroxydopamine (6-OHDA) into the unilateral medial forebrain bundle of the rat brain. DXM (20 mg/kg) was administered intraperitoneally twice daily from 7 days before the appearance of a 6-OHDA lesion to 28 days after the lesion appeared. The availability of dopamine transporter (DAT) and serotonin transporter (SERT) in the striatum of the rat brain was measured using positron emission tomography. The apomorphine-induced rotation test was performed to study the hypersensitivity of the brain regions with lesions. This animal study demonstrated that DXM significantly attenuated 6-OHDA-induced DAT and SERT loss, correlating to rotational behaviors. The population-based human study analyzed the data from the Taiwan Longitudinal Health Insurance Database 2005 between January 2005 and December 2013 and then used the DXM dose-response curve to investigate the trend of its protective effect against PD. In the human study, low cumulative doses of DXM may potentially achieve a protective effect for PD; however, high cumulative doses seem to be a risk for PD., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Methamphetamine (METH)-associated alterations in the striatal dopamine (DA) system or dopamine transport (DAT) have been identified in clinical and preclinical studies with positron emission tomography (PET) imaging but have not been well correlated with in vivo serotonin transporter (SERT) availability due to the lack of appropriate imaging agents to assess SERTs. N,N-dimethyl-2-(2-amino-4-[ 18 F]-fluorophenylthio) benzylamine (4-[ 18 F]-ADAM) has been developed by our group and validated for its high affinity and selectivity for SERTs, allowing the in vivo examination of SERT density, location, and binding function. The aims of this study were to investigate the potential of SERT imaging using 4-[ 18 F]-ADAM PET to estimate the long-lasting effects of METH-induced serotonergic neurotoxicity, and further determine whether a correlative relationship exists between SERT availability/activity and tyrosine hydroxylase (TH) activity in various brain regions due to the long-lasting consequences of METH treatment., Results: Male rats received four administrations of METH (5 or 10 mg/kg, s.c.) or saline (1 ml/kg, s.c.) at 1-h intervals. At 30 days post-administration, in vivo SERT availability and activity were measured by 4-[ 18 F]ADAM PET imaging. In contrast to the controls, the uptake of 4-[ 18 F]ADAM in METH-treated mice was significantly reduced in a dose-dependent manner in the midbrain, followed by the hypothalamus, thalamus, striatum, hippocampus, and frontal cortex. The regional effects of METH on TH activity were assessed by quantitative immunohistochemistry and presented as integrated optical density (IOD). A significant decrease in TH immunostaining and IOD ratios was seen in the caudate, putamen, nucleus accumbens, substantia nigra pars compacta, and substantia nigra pars reticulata in the METH-treated rats compared to controls., Conclusion: The present results suggested that the long-lasting response to METH decreased the uptake of 4-[ 18 F]-ADAM and varied regionally along with TH immunoreactivity. In addition, 4-[ 18 F]ADAM PET could be used to detect serotonergic neuron loss and to evaluate the severity of serotonergic neurotoxicity of METH.

This study investigated the protective effects of dextromethorphan (DXM) on noise-induced hearing loss (NIHL) in rats. This study aimed to improve the auditory threshold and to understand the protective effects of DXM against N-methyl-d-aspartate (NMDA)-induced neurite degeneration of serotonergic neurons. The animals were exposed to 8-kHz narrowband noise at a 118-dB sound pressure level for 3.5 h. The hearing thresholds were determined by measuring the auditory brainstem response to click stimuli. Serotonin transporter (SERT) expression was determined through micro-positron emission tomography (PET) using N,N-dimethyl-2-(2-amino-4- 18 F-fluorophenylthio)benzylamine (4-[ 18 F]-ADAM). We also investigated the effects of DXM on NMDA-induced morphological changes in the primary cultures of rat serotonergic neurons. NIHL significantly improved after prophylactic treatment with DXM (p < .05). SERT density in DXM-treated rats was significantly higher than that in non-DXM-treated rats. Because prophylactic medication restored the NMDA-inhibited neurite length of serotonergic neurons and presented SERT density, DXM could be a potential agent in alleviating NIHL., (Copyright © 2019 Elsevier Inc. All rights reserved.)

[18F]T807 is a potent tau protein imaging agent. In order to fulfill the demand from preclinical and clinical studies, we developed an automated one-pot two-step synthesis of this potent tau imaging agent and studied its stability, and dosimetry in mice and monkeys. We also conducted a preliminary study of this imaging agent in humans. Using this one-pot two-step method, the radiochemical yield (RCY) of [18F]T807 was 20.5 ± 6.1% (n = 15) at the end of bombardment (EOB) in a synthesis time of 70±5 min. The chemical and radiochemical purities were >90% and the specific activities were 151 ± 52 GBq/μmol. The quality of [18F]T807 synthesized by this method met the U.S. Pharmacopoeia (USP) criteria. The stability test showed that the [18F]T807 injection was stable at room temperature for up to 4 h after the end of synthesis (EOS). The estimated effective dose of the [18F]T807 injection extrapolated from monkeys was 19 μSv/MBq (n = 2), while the estimated effective doses of the [18F]T807 injection extrapolated from fasted and non-fasted mice were 123 ± 27 (n = 3) and 94 ± 19 (n = 4) μSv/MBq, respectively. This one-pot two-step automated method produced the [18F]T807 injection with high reproducibility and high quality. PET imaging and radiation dosimetry evaluation in mice and Formosan rock monkeys suggested that the [18F]T807 injection synthesized by this method is suitable for use in human PET imaging studies. Thus, this method could fulfill the demand for the [18F]T807 injection in both preclinical and clinical studies of tauopathies, especially for nearby study sites without cyclotrons., Competing Interests: The authors have declared that no competing interests exist.

One of the hallmarks of cancer is increased cell proliferation. Measurements of cell proliferation by estimation of DNA synthesis with several radiolabeled nucleosides have been tested to assess tumor growth. Deoxycytidine can be phosphorylated by deoxycytidine kinase (dCK) and is incorporated into DNA. This study evaluated a radiofluorinated deoxycytidine analog, 5-[ 18 F]fluoro-2'-deoxycytidine ([ 18 F]FdCyd), as a proliferation probe and compared it with 5-[ 18 F]fluoro-2'-deoxyuridine ([ 18 F]FdUrd), 3'-deoxy-3'-[ 18 F]fluorothymidine ([ 18 F]FLT), and [ 18 F]fluorodeoxyglucose ([ 18 F]FDG) in a tumor-bearing mouse model. [ 18 F]FdCyd was synthesized from two precursors by direct electrophilic substitution. The serum stability and partition coefficient of [ 18 F]FdCyd were evaluated in vitro. Positron emission topography (PET) imaging of Lewis lung carcinoma (LLC)-bearing mice with [ 18 F]FdCyd, [ 18 F]FdUrd, [ 18 F]FLT, and [ 18 F]FDG were evaluated. [ 18 F]FdCyd was stable in mouse serum and normal saline for up to 4 h. With all radiotracers except [ 18 F]FLT, PET can clearly delineate the tumor lesion. [ 18 F]FdCyd and [ 18 F]FdUrd showed high accumulation in the liver and kidney. The SUV and tumor-to-muscle (T/M) ratios derived from PET imaging of the radiotracers were [ 18 F]FDG > [ 18 F]FdCyd > [ 18 F]FdUrd > [ 18 F]FLT. Selective retention in tumors with a favorable tumor/muscle ratio makes [ 18 F]FdCyd a protential candidate for further investigation as a proliferation imaging agent., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Serotonin (5-HT) plays a crucial role in modulating the afferent fiber discharge rate in the inferior colliculus, auditory cortex, and other nuclei of the ascending auditory system. Resveratrol, a natural polyphenol phytoalexin, can inhibit serotonin transporters (SERT) to increase synaptic 5-HT levels. In this study, we investigated the effects of resveratrol on noise-induced damage in the serotonergic system. Male Sprague-Dawley rats were anaesthetized and exposed to an 8-kHz tone at 116 dB for 3.5 h. Resveratrol (30 mg/kg, intraperitoneal injection [IP]) and citalopram (20 mg/kg, IP), a specific SERT inhibitor used as a positive control, were administered once a day for four consecutive days, with the first treatment occurring 2 days before noise exposure. Auditory brainstem response testing and positron emission tomography (PET) with N , N -dimethyl-2-(2-amino-4-[ 18 F]fluorophenylthio)benzylamine (4-[ 18 F]-ADAM, a specific radioligand for SERT) were used to evaluate functionality of the auditory system and integrity of the serotonergic system, respectively, before and after noise exposure. Finally, immunohistochemistry was performed 1 day after the last PET scan. Our results indicate that noise-induced serotonergic fiber loss occurred in multiple brain regions including the midbrain, thalamus, hypothalamus, striatum, auditory cortex, and frontal cortex. This noise-induced damage to the serotonergic system was ameliorated in response to treatment with resveratrol and citalopram. However, noise exposure increased the hearing threshold in the rats regardless of drug treatment status. We conclude that resveratrol has protective effects against noise-induced loss of SERT.

The 3,4-methylenedioxymethamphetamine (MDMA) is a popular recreational drug, which ultimately leads to serotonergic (5-HT) neurotoxicity and psychiatric disorders. Previous in vitro studies have consistently demonstrated that MDMA provokes autophagic activation, as well as damage of 5-HT axons and nerve fibers. So far, whether autophagy, a well-conserved cellular process that is critical for cell fate, also participates in MDMA-induced neurotoxicity in vivo remains elusive. Here, we first examined time-course of autophagy-related changes during repeated administration of MDMA (10 mg/kg s.c. twice daily for 4 consecutive days) using immunofluorescent staining for tryptophan hydroxylase and microtubule-associated protein 1 light chain 3 beta in rats. We also evaluated the protective effects of 3-methyadanine (3-MA, an autophagy inhibitor, 15 mg/kg i.p.) against MDMA-induced acute and long-term reductions in serotonin transporters (SERT) density in various brain regions using immunohistochemical staining and positron emission tomography (PET) imaging respectively. Plasma corticosterone measurements and forced swim tests were performed to evaluate the depressive performance. The staining results showed that repeated administration of MDMA increased expression of autophagosome and caused reduction in SERT densities of striatum and frontal cortex, which was ameliorated in the presence of 3-MA. PET imaging data also revealed that 3-MA could ameliorate MDMA-induced long-term decreased SERT availability in various brain regions of rats. Furthermore, immobility time of forced swim tests and plasma corticosterone levels were less in the group of MDMA co-injected with 3-MA compared with that of MDMA group. Together, these findings suggest that autophagy inhibition may confer protection against neurobiological and behavioral changes induced by MDMA., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Purpose: (4S)-4-(3- 18 F-Fluoropropyl)-L-glutamate (FSPG) positron emission tomography (PET) reflects system x C - transporter (xCT) expression. FSPG PET has been used to detect brain, lung, breast and liver cancer with only modest success. There is no report on the use of FSPG PET in pancreatic ductal adenocarcinoma (PDAC), presumably because of normal xCT expression in the pancreas. Nonetheless, the tissue-specific expression of xCT in the pancreas suggests that FSPG PET may be ideal for identifying metastasized PDAC., Methods: The performance of FSPG in detecting PDAC metastases was compared with that of 18 F-fluorodeoxyglucose (FDG) in small-animal PET studies in seven PDAC tumour-bearing mice and in prospective PET/computed tomography (CT) studies in 23 patients with tissue-confirmed PDAC of stage III or stage IV. All PET/CT results were correlated with the results of histopathology or contrast-enhanced CT (ceCT) performed 3 and 6 months later., Results: In the rodent model, FSPG PET consistently found more PDAC metastases earlier than FDG PET. FSPG PET showed a trend for a higher sensitivity, specificity and diagnostic accuracy than FDG PET in detecting PDAC metastases in a patient-based analysis: 95.0%, 100.0% and 95.7%, and 90.0%, 66.7% and 90.0%, respectively. In a lesion-based analysis, FSPG PET identified significantly more PDAC metastases, especially in the liver, than FDG PET (109 vs. 95; P = 0.0001, 95% CI 4.9-14.6). The tumour-to-background ratios for FSPG and FDG uptake on positive scans were similar (FSPG 4.2 ± 4.3, FDG 3.6 ± 3.0; P = 0.44, 95% CI -1.11 to 0.48), despite a lower tumour maximum standardized uptake value in FSPG-avid lesions (FSPG 4.2 + 2.3, FDG 7.7 + 5.7; P = 0.002, 95% CI 0.70-4.10). Because of the lower physiological activity of FSPG in the liver, FSPG PET images of the liver are more easy to interpret than FDG PET images, and therefore the use of FSPG improves the detection of liver metastasis., Conclusion: FSPG PET is superior to FDG PET in detecting metastasized PDAC, especially in the liver.

Background: Neuritic plaques and neurofibrillary tangles are the pathological hallmarks of Alzheimer's disease (AD), while the role of brain amyloid deposition in the clinical manifestation or brain atrophy remains unresolved. We aimed to explore the relation between brain amyloid deposition, cortical thickness, and plasma biomarkers. Methods: We used 11 C-Pittsburgh compound B-positron emission tomography to assay brain amyloid deposition, magnetic resonance imaging to estimate cortical thickness, and an immunomagnetic reduction assay to measure plasma biomarkers. We recruited 39 controls, 25 subjects with amnesic mild cognitive impairment (aMCI), and 16 subjects with AD. PiB positivity (PiB+) was defined by the upper limit of the 95% confidence interval of the mean cortical SUVR from six predefined regions (1.0511 in this study). Results: All plasma biomarkers showed significant between-group differences. The plasma Aβ 40 level was positively correlated with the mean cortical thickness of both the PiB+ and PiB- subjects. The plasma Aβ 40 level of the subjects who were PiB+ was negatively correlated with brain amyloid deposition. In addition, the plasma tau level was negatively correlated with cortical thickness in both the PiB+ and PiB- subjects. Moreover, cortical thickness was negatively correlated with brain amyloid deposition in the PiB+ subjects. In addition, the cut-off point of plasma tau for differentiating between controls and AD was higher in the PiB- group than in the PiB+ group (37.5 versus 25.6 pg/ml, respectively). Lastly, ApoE4 increased the PiB+ rate in the aMCI and control groups. Conclusion: The contributions of brain amyloid deposition to cortical atrophy are spatially distinct. Plasma Aβ 40 might be a protective indicator of less brain amyloid deposition and cortical atrophy. It takes more tau pathology to reach the same level of cognitive decline in subjects without brain amyloid deposition, and ApoE4 plays an early role in amyloid pathogenesis.

Introduction: [ 18 F]Fluoromethylcholine ([ 18 F]FCH) is a potent tumors imaging agent. In order to fulfill the demand of pre-clinical and clinical studies, we have developed an automated high yield one-pot synthesis of this potent tumors imaging agent., Methods: [ 18 F]FCH was synthesized using a modified TRACERlab Fx FN module. Briefly, dibromomethane (10% in CH 3 CN) was fluorinated with K[ 18 F]/K 2.2.2 in a glassy carbon reaction vessel at 120°C for about 5min to generate [ 18 F]fluorobromomethane ([ 18 F]FBM). The resulting [ 18 F]FBM was then bubbling (He, 700mL/min) through four Sep-Pak® Silica Plus Long cartridges to react with dimethylaminoethanol (10% DMAE in 0.3mL DMSO) which was pre-loaded on Sep-Pak® C 18 Plus Short cartridge. The [ 18 F]FCH was purified by solid-phase extraction (SPE) using one Sep-Pak® C 18 Plus Short and one Sep-Pak® CM Plus Short in series. The quality of [ 18 F]FCH synthesized by this method was verified by HPLC and TLC as compared to authentic sample., Results: Using this improved one-pot method, the RCY of [ 18 F]FCH was 18.8 ± 2.1% (EOB, n = 27) in a synthesis time of 49 ± 5min from EOB. The radiochemical purity of [ 18 F]FCH was greater than 90% and the residual DMAE concentration in the final product was less than 10ppm., Conclusions: This optimized method could fulfill the demand of [ 18 F]FCH for both pre-clinical and clinical studies, especially for nearby study sites without a cyclotron., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The pathology of Parkinson's disease (PD) results mainly from nigrostriatal pathway damage. Unfortunately, commonly used PD therapies do not repair the disconnected circuitry. It has been reported that using kainic acid (KA, an excitatory amino acid) in bridging transplantation may be useful to generate an artificial tract and reconstruct the nigrostriatal pathway in 6-hydroxydopamine (6-OHDA) lesioned rats. In this study, we used KA bridging and a co-graft of rat olfactory ensheathing cells (OECs) and rat E14 embryonic ventral mesencephalic (VM) tissue to restore the nigrostriatal pathway of the PD model rats. The methamphetamine-induced rotational behaviour, 4-[ 18 F]-ADAM (a selectively serotonin transporter radioligand)/micro-PET imaging, and immunohistochemistry were used to assess the effects of the transplantation. At 9 weeks post-grafting in PD model rats, the results showed that the PD rats undergoing VM tissue and OECs co-grafts (VM-OECs) exhibited better motor recovery compared to the rats receiving VM tissue transplantation only. The striatal uptake of 4-[ 18 F]-ADAM and tyrosine hydroxylase immunoreactivity (TH-ir) of the grafted area in the VM-OECs group were also more improved than those of the VM alone group. These results suggested that OECs may enhance the survival of the grafted VM tissue and facilitate the recovery of motor function after VM transplantation. Moreover, OECs possibly promote the elongation of dopaminergic and serotonergic axon in the bridging graft. Copyright © 2015 John Wiley & Sons, Ltd., (Copyright © 2015 John Wiley & Sons, Ltd.)

Background/purpose: The aims of the current study were to determine whether patients with conduct disorder (CD) showed an abnormal availability of serotonin reuptake transporter (SERT), and if their hyperkinetic symptoms, impulsivity, and quality of life were correlated with the availability of SERT., Methods: We recruited 14 drug-naïve patients with CD and eight age-matched healthy controls (HCs). The adult attention-deficit/hyperactivity disorder (ADHD) self-report scale (ASRS), Barrett impulsivity scale (BIS), and the World Health Organization quality of life-brief version (WHOQOL-BREF) scale were administered. Positron emission tomography (PET) of the brain with 4-[ 18 F]-ADAM was arranged for SERT imaging., Results: SERT availability was significantly reduced in the striatum and midbrain of patients with CD. Quality of life and inattention symptoms were also significantly correlated with the availability of SERT in the prefrontal cortex., Conclusion: The study suggested that a reduction in the availability of SERT might be associated with CD and could potentially predict poor quality of life or symptoms of inattention for these patients. The implications of our results might be limited to individuals with CD; a future study with a larger sample to validate our preliminary results is warranted., (Copyright © 2016. Published by Elsevier B.V.)

Objective: The GE FASTlab radiosynthesis module is routinely used for the production of [(18)F]FDG, utilizing the commercially available phosphate cassettes. Because of the observation of a white precipitate in the product vial before the product expiry time, we re-examined the quality of the produced [(18)F]FDG solution., Methods: Phosphate buffered [(18)F]FDG solution was synthesized on the FASTlab and analyzed at both National Taiwan University Hospital (NTUH) of Taiwan and Royal Brisbane and Women's Hospital (RBWH) of Australia. In addition to the standard product quality control (QC), the concentration of aluminum (Al(3+)) as probable cause of the precipitations in the [(18)F]FDG solution was analyzed by inductively coupled plasma mass spectrometry (ICP-MS at RBWH) and inductively coupled plasma optical emission spectrometry (ICP-OES at NTUH), and using three semi-quantitative methods at NTUH, Advantec(®) Alumi Check Test Strip, Quantofix(®) Aluminum Test Strip and MColortest™ Aluminum Test kit., Results: The precipitates were observed in the [(18)F]FDG solution within 24 (NTUH) and 6 (RBWH) hours after the end of synthesis in 38-100 % of the batches, dependent on the batch of the FASTlab cassettes. Addition of metal-free HCl(aq) to aliquots of [(18)F]FDG containing precipitate, followed by ICP-MS analysis revealed Al(3+) concentrations of 70-80 ppm. Al(3+) concentrations of 10-12 ppm were detected in [(18)F]FDG batches that did not show any precipitation. In contrast, less than 5 ppm of the residual Al(3+) was detected by semi-quantitative methods in all batches., Conclusion: The US (USP), British (BP), European (EP) and Japanese (JP) pharmacopeias demand that [(18)F]FDG for injection should be clear and particulate free within the given shelf-life/expiration time. To avoid Al-phosphate precipitation within the product expiry time, FASTlab citrate cassettes, rather than phosphate cassettes, should be used for [(18)F]FDG production. Although testing for Al(3+) is not listed in the [(18)F]FDG monographs of the USP, BP and EP, residual Al(3+) levels should be considered in the interests of patient safety.

In the early 1990s, 9-(+)-11C-dihydrotetrabenazine (9-(+)-11C-DTBZ) was shown to be a useful positron emission tomography (PET) imaging agent for various neurodegenerative disorders. Here, we described the radiosynthesis and evaluation of the 9-(+)-11C-DTBZ analog, 10-(+)-11C-DTBZ, as a vesicular monoamine transporter 2 (VMAT2) imaging agent and compare it with 9-(+)-11C-DTBZ. 10-(+)-11C-DTBZ was obtained by 11C-MeI methylation with its 10 hydroxy precursor in the presence of 5 M NaOH. It had a slightly better average radiochemical yield of 35.3 ± 3.6% (decay-corrected to end of synthesis (EOS)) than did 9-(+)-11C-DTBZ (30.5 ± 2.3%). MicroPET studies showed that 10-(+)-11C-DTBZ had a striatum-to-cerebellum ratio of 3.74 ± 0.21 at 40 min post-injection, while the ratio of 9-(+)-11C-DTBZ was 2.50 ± 0.33. This indicated that 10-(+)-11C-DTBZ has a higher specific uptake in VMAT2-rich brain regions, and 10-(+)-11C-DTBZ may be a potential VMAT2 radioligand. Our experiment is the first study of 10-(+)-11C-DTBZ to include dynamic brain distribution in rat brains., Competing Interests: The authors have declared that no competing interests exist.

Introduction: N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM, 2) is a potent serotonin transporter (SERT) imaging agent. In order to fulfill the demand of clinical studies, we have developed a fully automated one-pot two-step synthesis of this potent SERT imaging agent., Methods: The 4-[(18)F]-ADAM (2) was synthesized using a commercially available GE TRACERlab FN module. Briefly, the precursor, N,N-dimethyl-2-(2,4-dinitrophenylthio) benzylamine (1) in DMSO was reacted with K[(18)F]/K2.2.2 in a glassy carbon reaction vessel at 120°C for 7.5min followed by reduction of the intermediate with NaBH4/Cu(OAc)2 in EtOH in the same vessel at 80°C for 20min. The reaction mixture was then purified with high-performance liquid chromatography (HPLC) and solid phase extraction (SPE) to give (2). The quality of (2) synthesized by this method was verified by HPLC and TLC as compared to its authentic sample synthesized by two-pot two-step method., Results: Using this automated one-pot two-step method, the radiochemical yield (RCY) of (2) was 2.5±0.8% (n=12, EOS) in a synthesis time of 100±6min from EOB with a specific activity of 4.4±1.9Ci/μmol (n=12, EOS). Radioligand (2) was stable over 4h at room temperature., Conclusions: This fully automated one-pot two-step synthetic method using a commercially available GE TRACERlab FN module could simplify the synthesis of 4-[(18)F]-ADAM (2) and fulfill its demand for both animal and human studies, especially for study sites without a cyclotron., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Parkinson's disease (PD) is a neurodegenerative disease characterized by a loss of dopaminergic neurons in the nigrostriatal pathway. Apart from effective strategies to halt the underlying neuronal degeneration, cell replacement now offers novel prospects for PD therapy. Porcine embryonic neural tissue has been considered an alternative source to human fetal grafts in neurodegenerative disorders because its use avoids major practical and ethical issues. This study was undertaken to evaluate the effects of embryonic day 27 (E27) porcine mesencephalic tissue transplantation in a PD rat model using animal positron emission tomography (PET) coupled with 4-[(18)F]-ADAM, a serotonin transporter (SERT) imaging agent. The parkinsonian rat was induced by injecting 6-hydroxydopamine into the medial forebrain bundle (MFB) of the right nigrostriatal pathway. The apomorphine-induced rotation behavioral test and 4-[(18)F]-ADAM/animal PET scanning were carried out following 6-OHDA lesioning. At the second week following 6-OHDA lesioning, the parkinsonian rat rotates substantially on apomorphine-induced contralateral turning. In addition, the mean striatal-specific uptake ratio (SUR) of 4-[(18)F]-ADAM decreased by 44%. After transplantation, the number of drug-induced rotations decreased markedly, and the mean SUR of 4-[(18)F]-ADAM and the level of SERT immunoreactivity (SERT-ir) in striatum were partially restored. The mean SUR level was restored to 71% compared to that for the contralateral intact side, which together with the abundant survival of tyrosine hydroxylase (TH) neurons accounted for functional recovery at the fourth week postgraft. In regard to the extent of donor-derived cells, we found the neurons of the xenografts from E27 transgenic pigs harboring red fluorescent protein (RFP) localized with TH-ir cells and SERT-ir in the grafted area. Thus, transplanted E27 porcine mesencephalic tissue may restore dopaminergic and serotonergic systems in the parkinsonian rat. The 4-[(18)F]-ADAM/animal PET can be used to detect serotonergic neuron loss in PD and monitor the efficacy of therapy.

The misuse of 3,4-methylenedioxymethamphetamine (MDMA) has drawn a growing concern worldwide for its psychophysiological impacts on humans. MDMA abusers are often accompanied by long-term serotonergic neurotoxicity, which is associated with reduced density of cerebral serotonin transporters (SERT) and depressive disorders. Resveratrol (RSV) is a natural polyphenolic phytoalexin that has been known for its antidepressant and neuroprotective effects. However, biological targets of RSV as well as its neuroprotective effects against MDMA remained largely unknown. In this study, we examined binding potency of RSV and MDMA to SERT using small-animal positron emission tomography (PET) with the SERT radioligand, N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM) and investigated the protection of RSV against the acute and long-term adverse effects of MDMA. We found that RSV exhibit binding potentials to SERT in vivo in a dose-dependent manner with variation among brain regions. When the MDMA-treated rats (10mg/kg, s.c.) were co-injected with RSV (20mg/kg, i.p.) twice daily for 4 consecutive days, MDMA-induced acute elevation in plasma corticosterone was significantly reduced. Further, 4-[(18)F]-ADAM PET imaging revealed that RSV protected against the MDMA-induced decrease in SERT availability in the midbrain and the thalamus 2 weeks following the co-treatment. The PET data were comparable to the observation from the forced swim test that RSV sufficiently ameliorated the depressive-like behaviors of the MDMA-treated rats. Together, these findings suggest that RSV is a potential antidepressant and may confer protection against neurobiological and behavioral changes induced by MDMA., (Copyright © 2015 Elsevier B.V. and ECNP. All rights reserved.)

Objectives: Suicide is an important issue in the military service, since it can influence military morale and create dangerous situations for other personnel. The serotonin transporter (SERT) has been suggested to be involved in the pathophysiology of depression and suicidal behaviours. The aims of this study were to examine whether the brain SERT availability differs between military conscripts with depression and control subjects, and whether suicidal ideation is correlated with SERT availability., Methods: We used N,N-dimethyl-2-(2-amino-4-[(18)F]-fluorophenylthio)benzylamine (4-[(18)F]-ADAM) as a radioligand for positron emission tomography (PET) imaging. All participants completed the Hamilton Depression Rating Scale and Beck Scale for Suicide Ideation (BSS) prior to PET imaging., Results: The effect of major depression and BSS scores had an interaction on SERT availability. After adjusting for the BSS score, subjects with depression had lower SERT availability than control subjects (F1,17 = 23.85, P < 0.001). A positive correlation between SERT availability and BSS scores was observed in the depression group (F1,8 = 30.67, P = 0.001). The status of depression and intensity of suicidal ideation exert opposite effects on SERT availability., Conclusions: The extent of suicidal ideation may moderate the reduction effect in SERT binding observed in major depression in male military conscripts.

Objective: PET imaging with (18)F-FDOPA has been successfully applied in the diagnosis and surveillance of neuroblastoma (NB) by targeting the overexpression of aromatic L-amino acid decarboxylase. This study aims to assess the impact of residual (18)F-fluoride on (18)F-FDOPA PET in NB and to implement a method to maintain low (18)F-fluoride content in future studies., Methods: Automatic synthesis of (18)F-FDOPA was based on the electrophilic method using TRACERlab FXFE module. Radio-TLC was employed to determine residual (18)F-fluoride levels. We analyzed the impact of residual (18)F-fluoride on the images of 35 patients undergoing (18)F-FDOPA PET at initial diagnosis and/or follow-ups of NB., Results: In 35 batches of (18)F-FDOPA products from 9/28/2010 to 07/27/2011, the mean residual (18)F-fluoride level was 4.4 % (range 0.2-19.1 %). Residual (18)F-fluoride level ≥4.0 % was associated with dense uptake in the growth plates, skull, and pelvis on PET scans, which may interfere with the interpretation of (18)F-FDOPA imaging in NB. By applying stringent restraints in (18)F-FDOPA production, including regular renewal of reagents, exclusive use  of NH4OH, and timely replacement of HPLC column, the incidence of (18)F-FDOPA batches with residual (18)F-fluoride level ≥4.0 % was reduced from 33 to 4 % (P < 0.0001) during 7/30/2011-4/29/2013., Conclusion: By monitoring residual (18)F-fluoride levels and keeping stringent restraint procedures, low (18)F-fluoride content was achieved in most batches of (18)F-FDOPA, which diminished false-positive skeletal uptake. An appropriate upper limit of (18)F-fluoride level is suggested to be included in the criteria of routine quality control of (18)F-FDOPA productions.

Background: Many lines of evidence suggest the role of serotonin transporter (SERT)-mediated reuptake of serotonin in the pathophysiology and treatment of major depressive disorder (MDD). This study aimed to examine whether the pretreatment of SERT binding potential or SERT binding ratio between terminal projection regions relative to the midbrain raphe nuclei was associated with treatment outcomes to SERT-targeted antidepressants., Methods: We recruited 39 antidepressant-naïve patients with MDD and 39 heathy controls. Positron emission tomography with N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM) was used to measure in vivo SERT availability prior to antidepressant treatment. The 21-item Hamilton Depression Rating Scale (HDRS) was use to assess the severity of depression from baseline to week 6. All the patients with MDD had HDRS scores of 18 or more., Results: Pretreatment SERT binding in the thalamus and striatum positively correlated with an early reduction in HDRS scores at week 3. Nonresponders and dropout patients showed a proportionate reduction in SERT binding in the terminal projection regions and midbrain compared to healthy controls. In contrast, a disproportionate reduction in SERT binding in the terminal projection regions relative to midbrain was observed in responders., Conclusions: The results of this study suggested that a disproportionate reduction in SERT binding between terminal projection regions and midbrain may predict better treatment outcomes in patients with MDD., (© The Author 2015. Published by Oxford University Press on behalf of CINP.)

Background: [(18) F]AFM is a potent and promising PET imaging agent for the serotonin transporter. We carried out an acute toxicity study in rats and radiation dosimetry in monkeys before the translation of the tracer to humans., Methods: Single- and multiple-dose toxicity studies were conducted in Sprague-Dawley rats. Male and female rats were injected intravenously with AFM tartrate as a single dose of 98.7 or 987 μg/kg (592 or 5,920 μg/m(2), 100× or 1,000× the proposed human dose of 8 μg, respectively) on day 1 or as five consecutive daily doses of 98.7 μg/kg/day (592 μg /m(2)/day, 100× human dose, total dose 493.5 μg/kg). PET/CT scans were performed in four Formosan rock monkeys (two males and two females, each monkey scanned twice) using a Siemens BIOGRAPH scanner. After injection of [(18) F]AFM (88.5 ± 20.3 MBq), a low-dose CT scan and a series of eight whole-body PET scans in 3-D mode were performed. Time-activity data of source organs were used to calculate the residence times and estimate the absorbed radiation dose using the OLINDA/EXM software., Results: In the rats, neither the single dose nor the five daily doses of AFM tartrate produced overt adverse effects clinically. In the monkeys, the radiation doses received by most organs ranged between 8.3 and 39.1 μGy/MBq. The osteogenic cells, red marrow, and lungs received the highest doses of 39.1, 35.4, and 35.1 μGy/MBq, respectively. The effective doses extrapolated to male and female adult humans were 18.0 and 18.3 μSv/MBq, respectively., Conclusions: Toxicity studies in Sprague-Dawley rats and radiation dosimetry studies in Formosa rock monkeys suggest that [(18) F]AFM is safe for use in human PET imaging studies., Trial Registration: IACUC-12-200.

Background: Much evidence supports the role of the serotonin transporter (SERT) in the pathophysiology and pharmacotherapy of major depressive disorder (MDD) and suicidal behaviors., Methods: In this study, we recruited 17 antidepressant-naïve patients with MDD and 17 age- and gender-matched healthy controls. SERT availability was measured in vivo with N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM) positron emission tomography (PET) imaging. The 21-item Hamilton Depression Rating Scale (HDRS) and Beck Scale for Suicide Ideation were used to assess the severity of depression and the intent of suicide ideation prior to PET imaging. All subjects with MDD were in a current state of depression with HDRS scores ≧18. Subjects who attempted suicide within two weeks of the study onset were recruited in the depressed suicidal group (n = 8). Subjects with MDD who denied any prior suicide attempt were recruited into the depressed non-suicidal group (n = 9)., Results: A significant reduction of SERT availability in the midbrain, thalamus, and striatum was noted in the MDD group relative to the control group (Bonferroni-adjusted p-value < 0.05). Moreover, this effect was more pronounced in the depressed suicidal group compared to the control group (Bonferroni-adjusted p-value < 0.01). Relative to both the depressed non-suicidal and control groups, the depressed suicidal group showed an increased prefrontal cortex (PFC)/midbrain SERT binding ratio (Bonferroni-adjusted p-value < 0.01)., Conclusions: This study suggests an incongruent reduction of PFC SERT binding relative to the midbrain might discriminate between depressed suicide attempters and non-attempters in patients with MDD and may be involved in the pathophysiology of suicide behaviors., (© The Author 2015. Published by Oxford University Press on behalf of CINP.)

Recent advances in biomarkers provide the possibility of early or preclinical diagnosis of Alzheimer's pathology. Currently, decreased levels of Aβ-42 and increased levels of tau proteins in cerebral spinal fluid are considered reliable biomarkers of Alzheimer's disease (AD); however, little evidence exists for the use of amyloid and tau protein levels in the plasma as useful biomarkers. We investigated the potential use of plasma biomarkers to diagnose AD and explored their relationships with brain Aβ deposition in amyloid imaging. We used an immunomagnetic reduction assay to measure the plasma levels of Aβ40, Aβ42, and tau proteins in 20 older control participants and 25 participants who had either mild cognitive impairment due to AD or early AD dementia. All participants received (11)C-labeled Pittsburgh compound B PET scans. The sensitivity of the plasma tau level at the cutoff value of 28.27 pg/mL was 92%, and the specificity was 100%; the sensitivity of the Aβ42/40 ratio at the cutoff value of 0.3693 was 84%, and the specificity was 100%. Regression analyses of the effects of plasma protein levels on brain amyloid retention, as determined by standard uptake value ratios in either side of the frontal, parietal, and temporal lobes and the precuneus, are predicted only by ratios of plasma Aβ42/40 (R(2) 0.326-0.449, all p < 0.001) but not by plasma tau levels. Plasma Aβ in terms of Aβ42/40 might provide an indirect estimation of Aβ deposition in the brain.

The serotonin transporter (SERT) is an important marker of the status of serotonergic neurons. The main function of SERT is to regulate the serotonin concentration in the synapse. Recent studies have shown that SERT is expressed in the central auditory pathway and may play a role in the auditory process. However, little is known about the effects of noise on the cerebral serotonin system. In this study, we explored the status of brain SERT in a rat model of noise-induced hearing loss using 4-[(18)F]-ADAM (a SERT imaging agent) and small animal positron emission tomography (PET) imaging. Male Sprague Dawley rats were exposed to an 8 kHz noise at 118 dB sound pressure level for 3.5h. An auditory brainstem response test and 4-[(18)F]-ADAM/small animal PET were performed at different time points after noise exposure. The specific uptake ratios (SURs) for 4-[(18)F]-ADAM were calculated from the PET imaging data in six brain regions. Immunohistochemistry and surface preparation of the cochleae were performed 30 days after noise exposure. Our data clearly showed that the hearing and cochlear outer hair cells of the rats were lost after noise exposure. In the PET study, the SURs of SERT were markedly reduced by 35%-58% in various brain regions one day after noise exposure. The decrement remained on days 8 and 15 and was approximately 26%-48% on day 29. The distribution and intensity of SERT immunostaining in the brain paralleled the PET imaging data. These results suggest that noise-induced hearing loss involves a reduction in SERT expression in various regions of the rat brain and that changes in SERT are detectable by 4-[(18)F]-ADAM/small animal PET in vivo., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Purpose: The aim of this study was to assess the feasibility of using 4-[(18)F]-ADAM as a brain SERT imaging agent in humans., Methods: Enrolled in the study were 19 healthy Taiwanese subjects (11 men, 8 women; age 33 ± 9 years). The PET data were semiquantitatively analyzed and expressed as specific uptake ratios (SUR) and distribution volume ratios (DVR) using the software package PMOD. The SUR and DVR of 4-[(18)F]-ADAM in the raphe nucleus (RN), midbrain (MB), thalamus (TH), striatum (STR) and prefrontal cortex (PFC) were determined using the cerebellum (CB) as the reference region., Results: 4-[(18)F]-ADAM bound to known SERT-rich regions in human brain. The order of the regional brain uptake was MB (RN) > TH > STR > PFC > CB. The DVR (n = 4, t* = 60 min) in the RN, TH, STR and PFC were 3.00 ± 0.50, 2.25 ± 0.45, 2.05 ± 0.31 and 1.40 ± 0.13, respectively. The optimal time for imaging brain SERT with 4-[(18)F]-ADAM was 120-140 min after injection. At the optimal imaging time, the SURs (n = 15) in the MB, TH, STR, and PFC were 2.25 ± 0.20, 2.28 ± 0.20, 2.12 ± 0.18 and 1.47 ± 0.14, respectively. There were no significant differences in SERT availability between men and women (p < 0.05)., Conclusion: The results of this study showed that 4-[(18)F]-ADAM was safe for human studies and its distribution in human brain appeared to correlate well with the known distribution of SERT in the human brain. In addition, it had high specific binding and a reasonable optimal time for imaging brain SERT in humans. Thus, 4-[(18)F]-ADAM may be feasible for assessing the status of brain SERT in humans.

This study was undertaken to address the effects of fetal mesencephalic tissue transplantation on the serotonin system in a rat model of Parkinson's disease (PD) while also investigating the usefulness of 4-[18F]-ADAM (a serotonin transporter imaging agent) coupled with micro-PET for imaging serotonin transporters (SERTs). A PD model was induced by unilateral injection of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle of the nigrostriatal pathway, while cell transplantation was performed via intrastriatal injection of mesencephalic brain tissue dissected from embryonic (E14) rats. The 4-[18F]-ADAM/micro-PET scanning was performed following both 6-OHDA lesioning and transplantation. Immunohistochemistry (IHC) studies were also performed following the final PET scan, and the results were compared to show a 17-43% decrease in the specific uptake ratio (SUR) and a 23-52% decrease in serotonin transporter immunoreactivity (SERT-ir) within various brain regions on the lesioned side. The number of methamphetamine-induced rotations also decreased significantly at the 4th week postgraft. In addition, striatal SUR and the SERT-ir levels were restored to 77% and 83% 5 weeks postgraft. These results suggest that Parkinson's disease also affects the serotonergic system, while both the dopaminergic and serotonergic systems can be partially restored in a rat model of PD after E14 mesencephalic tissue transplantation. In addition, we have also determined that 4-[18F]-ADAM/micro-PET can be used to detect serotonergic neuron loss, monitor the progress of Parkinson's disease, and oversee the effectiveness of therapy.

4-[(18)F]F-ADAM (1a), 2-[(18)F]F-ADAM (2a), N-Desmethyl-4-[(18)F]F-ADAM (3a) and [(18)F]F-AFM (4a ) were synthesized in 1.7, 3.9, 2.9 and 0.6% yield (EOS), respectively, in a synthesis time of ~120 min from EOB. PET studies in rats showed that the maximum specific uptake ratios of 1a, 2a, 3a and 4a in midbrain were 3.86, 0.73, 0.35 and 2.23, respectively. Thus, in terms of radiochemical yield, specific binding and in vivo stability, 4-[(18)F]F-ADAM may be the most appropriate SERT imaging agent for human studies., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Single photon emission computed tomography (SPECT) with Tc-99m TRODAT-1 as ligand can be used to evaluate striatal dopamine transporters (DAT) in young subjects. The purpose of this study was to evaluate the reproducibility of (99m)Tc-TRODAT-1 SPECT in DAT binding in healthy young men. Fourteen healthy young men were recruited. The test-retest studies were performed 1week apart. Specific uptake ratios (SUR) of the striatum (ST) and its subregions, the caudate (CA) and the putamen (PU), were measured using the occipital cortex as the reference tissue. The reliability of the two measurements between test and retest, showed significant correlations for the ST, CA and PU, was demonstrated by calculating the intraclass correlation coefficient (ICC). Thus, (99m)Tc-TRODAT-1 SPECT might provide a reproducible and reliable tool in clinical management of young patients with DAT-related disorders., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Introduction: Serotonin transporter (SERT) has been associated with many psychiatric diseases. This study investigated the biodistribution of a serotonin transporter imaging agent, N,N-dimethyl-2-(2-amino-4-(18)F-fluorophenylthio)benzylamine (4-[(18)F]-ADAM), in nonhuman primate brain using positron emission tomography (PET)., Methods: Six and four Macaca cyclopis monkeys were used to determine the transit time (i.e., time necessary to reach biodistribution equilibrium) and the reproducibility of 4-[(18)F]-ADAM biodistribution in the brain, respectively. The sensitivity and specificity of 4-[(18)F]-ADAM binding to SERT were evaluated in one monkey challenged with different doses of fluoxetine and one monkey treated with 3,4-methylendioxymethamphetamine (MDMA). Dynamic PET imaging was performed for 3 h after 4-[(18)F]-ADAM intravenous bolus injection. The specific uptake ratios (SURs) in the midbrain (MB), thalamus (TH), striatum (ST) and frontal cortex (FC) were calculated., Results: The distribution of 4-[(18)F]-ADAM reached equilibrium 120-150 min after injection. The mean SURs were 2.49 ± 0.13 in MB, 1.59 ± 0.17 in TH, 1.35 ± 0.06 in ST and 0.34 ± 0.03 in FC, and the minimum variability was shown 120-150 min after 4-[(18)F]-ADAM injection. Using SURs and intraclass coefficient of correlation, the test/retest variability was under 8% and above 0.8, respectively, in SERT-rich areas. Challenge with fluoxetin (0.75-2 mg) dose-dependently inhibited the SURs in various brain regions. 4-[(18)F]-ADAM binding was markedly reduced in the brain of an MDMA-treated monkey compared to that in brains of normal controls., Conclusion: 4-[(18)F]-ADAM appears to be a highly selective radioligand for imaging SERT in monkey brain., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Purpose: 4-[(18)F]-ADAM is a potent serotonin transport imaging agent. We studied its toxicity in rats and radiation dosimetry in monkeys before human studies are undertaken., Methods: Single and multiple-dosage toxicity studies were conducted in Sprague-Dawley rats. Male and female rats were injected intravenously with 4-F-ADAM as a single dose of 1,023.7 microg/kg (1,000 times the human dose) or as five consecutive daily doses of 102.37 microg/kg (100 times the human dose). PET/CT scans were performed in seven Formosa Rock monkeys (four males and three females) using a Siemens Biograph scanner. After injection of 4-[(18)F]-ADAM (182+/-8 MBq), a low dose CT scan and a series of eight whole-body PET scans were performed. Whole-body images were acquired in 3-D mode. Time-activity data of source organs were used to calculate the residence times and estimate the absorbed radiation dose using OLINDA/EXM software., Results: In the rats neither the single dose nor the five daily doses of 4-F-ADAM produced overt adverse effects clinically. In the monkeys the radiation doses received by most organs ranged between 7.1 and 35.7 microGy/MBq, and the urinary bladder was considered to be the critical organ. The effective doses extrapolated to male and female adult humans were 17.4 and 21.8 microSv/MBq, respectively., Conclusion: Toxicity studies in Sprague-Dawley rats and radiation dosimetry studies in Formosa Rock monkeys suggested that 4-[(18)F]-ADAM is safe for use in human PET imaging studies.

3, 4-Methylenedioxymethamphetamine (MDMA, "ecstasy") has toxic effects on serotonergic neurons in the brain. Our aim was to determine whether N,N-dimethyl-2-(2-amino-4-[(18)F]-fluorophenylthio) benzylamine (4-[(18)F]-ADAM; a serotonin transporter imaging agent) and micropositron emission tomography (micro-PET) can be used to examine in vivo the effect of fluoxetine on MDMA-induced loss of serotonin transporters in rat brain. Male Sprague-Dawley rats were injected with fluoxetine [1 dose, 5 mg/kg, subcutaneously (s.c.)] followed by MDMA (twice a day for 4 consecutive days, 10 mg/kg, s.c.). Micro-PET with 4-[(18)F]-ADAM was performed on days 4, 10, 17, 24, and 31. In addition, the time course of occupancy by fluoxetine at 4-[(18)F]-ADAM sites was measured. Specific 4-[(18)F]-ADAM uptake ratios (SURs) were calculated from the micro-PET imaging data for various brain regions. Immunohistochemistry was performed 7 days after the last micro-PET scan. From day 4 to day 31, SURs were markedly decreased (by approximately 55-75% compared to control values) in all brain regions in MDMA-treated rats. The effect of MDMA was markedly attenuated (approximately 30-50%) by fluoxetine. The fluoxetine-induced decrease in uptake in different brain regions was 40-75% at 90-min postinjection, and this decrease returned to baseline values in most brain regions by day 31. The distribution and intensity of serotonin transporter (SERT) immunostaining in the brain paralleled the PET imaging results, suggesting that a single dose of fluoxetine provides long-lasting protection against MDMA-induced loss of SERT and that such neuroprotection is detectable in vivo by 4-[(18)F]-ADAM micro-PET.

An improved synthesis of N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM, 2) as a potent serotonin transporter (SERT) imaging agent is described. Molecular orbital (MO) calculation predicts that N,N-dimethyl-2-(2-nitro-4-trimethylammoniumtrifluoromethanesulfonylphenylthio)benzamide (8) is probably a better precursor than N,N-dimethyl-2-(2,4-dinitrophenylthio)benzylamine (1) for preparing 2. Radioligand 2 was synthesized by the reaction of either precursor 1 or precursor 8 with K[(18)F]/K(2.2.2) at 120 degrees C followed by reduction with BH(3) at 80 degrees C. The radiochemical yield (EOB) of 2 synthesized from precursor 1 and 8 was 5.7+/-2.4% (n=6) and 14.8+/-4.0% (n=5), respectively, in a synthesis time of 120 min from EOB. The specific activity of 2 was 3 Ci/micromol or 111 GBq/micromol (EOB). Thus, this new synthetic method has significantly improved the radiochemical yield of 4-[(18)F]-ADAM and makes this radioligand more accessible to PET Centers without a cyclotron.

Serotonin transporters (SERTs) have been implicated in various neuropsychiatric disorders. We aim to validate 4-[(18)F]-ADAM (N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine) as a SERT imaging agent in rats using micro-positron emission tomography (micro-PET) and autoradiography. Sixty to ninety min after injecting 4-[(18)F]-ADAM, specific uptake ratios (SURs) were determined by micro-PET measurements in various brain regions of normal control rats. For n=3, the SUR in the midbrain was 4.94+/-0.16, for the hypothalamus it was 4.39+/-0.031 and for the caudate it was 4.18+/-0.53. The retention of 4-[(18)F]-ADAM in the hypothalamus and midbrain regions increased rapidly between 5 to 10 min after injection and declined thereafter. The SURs determined by autoradiography were: 9.31+/-1.41 for the midbrain, 7.15+/-1.45 for the hypothalamus and 5.22+/-1.14 for the caudate putamen. Both micro-PET and autoradiography studies revealed a dose-dependent progressive inhibition of radioligand uptake in the frontal cortex, caudate putamen and hypothalamus in rats treated with 0.01 to 0.25 mg/kg paroxetine. A decrease in 4-[(18)F]-ADAM uptake of approximately 84% was observed in the midbrain of rats pretreated with 0.25 mg/kg paroxetine as compared to controls (4.94+/-0.16 versus 0.80+/-0.17, n=3). Both 5,7-dihydroxytryptamine and p-chloroamphetamine-treated rats showed pronounced reduction in 4-[(18)F]-ADAM binding when compared to normal controls. Rats pretreated with p-chloroamphetamine exhibited significant inhibition of 4-[(18)F]-ADAM uptake in brain regions rich in SERT over a period of four weeks. Thus, 4-[(18)F]-ADAM is a SERT-specific radioligand that may be useful for evaluating neuropsychiatric conditions involving serotonergic dysfunction.

N,N-dimethyl-2-(2-amino-4-[(18)F]fluorophenylthio)benzylamine (4-[(18)F]-ADAM, 3) is a potent serotonin transporter (SERT) imaging agent. In order to fulfill the demand of pre-clinical studies, we have developed an automated synthesis unit to synthesize this radioligand. The 4-[(18)F]-ADAM was synthesized using TracerLab FN and FE modules and a modified module control program (TracerLab-Fx). The synthesis sequences were similar to that of the manual synthesis, i.e. nucleophilic fluorination of N,N-dimethyl-2-(2,4-dinitrophenylthio)benzylamine (1) with K[(18)F]/K(2.2.2) followed by reduction with NaBH(4)/Cu(OAc)(2) and purifications with high-performance liquid chromatography (HPLC) and solid phase extraction. The radiochemical yield of 3 was 1.5+/-0.3% (n=13, EOS). The synthesis time was 120 min and the specific activity was 1.75+/-0.77 Ci/micromol (n=13, EOS). The 4-[(18)F]-ADAM synthesized by this module was stable over 4h at room temperature and is suitable for imaging SERT in humans.

Pancreatic islet cell mass (PICM) is a major determinant of the insulin secretory capacity in humans. Currently, the only method for accurate assessment of the PICM is an autopsy study. Thus, development of a technique allowing the non-invasive quantification of PICM is of great interest. The aim of this study was to develop such a non-invasive technique featuring novel fluorine- and (99m)Tc-labelled glibenclamide derivatives. Despite the structural modifications necessary to introduce fluorine into the glibenclamide molecule, all derivatives retained insulin stimulating capacity as well as high affinity binding to human SUR1 when compared to the original glibenclamide. Contrastingly, the lipophilicity of the fluorine-labelled derivatives was altered depending on the particular modification. In the human PET-study a constant but weak radioactive signal could be detected in the pancreas using a fluorine-labelled glibenclamide derivative. However, a reliable assessment and visualisation of the PICM could not be obtained. It can be assumed that the high uptake of the fluorine-labelled tracer e.g. into the the liver and the high plasma protein binding leads to a relatively low signal-to-noise ratio. In case of the presented fluorine-labelled glibenclamide based compounds this could be the result of their invariably high lipophilicity. The development of a (99 m)Tc-labelled glibenclamide derivative with a lower lipophilicity and differing in vivo behaviour, glibenclamide based compounds for non-invasive imaging of the pancreatic islet cell mass may be possible.

The synthesis and evaluation of a new serotonin transporter (SERT) imaging agent, N,N-dimethyl-2-(2-amino-5-[18F]fluorophenylthio)benzylamine (5-[18F]-ADAM) is reported. Nucleophilic substitution of N,N-dimethyl-2-(2-nitro-5-bromophenylthio)benzylamine with K[18F]/Kryptofix 2.2.2 in DMSO at 125 degrees C followed by reduction with NaBH4-Cu(OAc)2 in EtOH at 78 degrees C and purification with HPLC produces the desired compound with an unoptimized yield of approximately 5-10% in a synthesis time of 150 min from EOB. The biodistribution of 5-[18F]-ADAM in rats showed a high initial uptake and relatively rapid clearance in the brain (3.221+/-0.762, 0.440+/-0.059, 0.160+/-0.035 and 0.028+/-0.003% injected dose/organ at 2, 30, 60 and 120 min after I.V. injection, respectively) with the specific binding peaking at 1 h postinjection (hypothalamus/cerebellum and hippocampus/cerebellum were 2.97 and 3.59, respectively). The initial uptake in blood, lung, kidney and heart were also high, but it cleared rapidly. The radioactivity in the femur increased with time for 5-[18F]-ADAM indicating that in vivo defluorination may occur. Metabolism studies in rats showed that 5-[18F]-ADAM was not metabolized in rat brain, but was metabolized rapidly in the blood. Blocking experiments showed that there were significant decreases in the uptake of 5-[18F]-ADAM in the brain regions (hypothalamus, hippocampus and striatum) where SERT concentrations are high when rats were pretreated with (+)McN 5652 (2 mg/kg, 5 min prior to IV injection of 5-[18F]-ADAM). These results suggest that 5-[18F]-ADAM may be a potential new serotonin transporter PET imaging agent. However, due to its rapid wash-out from the brain, defluorination in vivo and lower uptake in the brain than 4-[18F]-ADAM, 5-[18F]-ADAM may not be as useful as 4-[18F]-ADAM as a SERT imaging agent.

Twenty-eight years after its inception, 2-[18F]FDG- is still the most widely used radiopharmaceutical for PET studies, but numerous more specific radiotracers have been developed and applied in neuroscience and oncology. The advances in radiotracer chemistry, especially the nucleophilic substitution reaction, have played the pivotal role in synthesizing various no-carrier-added 18F-labeled radiotracers for PET studies of various receptor systems. This article lists some of the radiotracers that are available for PET studies in neuroscience and oncology. The prospects for developing other new radiotracers for imaging other organ diseases also seem to be promising.

The 11C-labeled sulfonylurea receptor 1 (SUR1) ligand (S)-2-([11C]methoxy)-4-[3-methyl-1-(2-piperidine-1-yl-phenyl)-butyl-carbamoyl]-benzoic acid ([11C]methoxy-repaglinide) was synthesized in an overall radiochemical yield of 35% after 55 min with a radiochemical purity higher than 99%. This compound is considered for the noninvasive investigation of the SUR1 receptor status of pancreatic beta-cells by positron emission tomography (PET) in the context of type 1 and type 2 diabetes. The specific activity was 40-70 GBq/micromol. In vitro testing of the nonradioactive methoxy-repaglinide was performed to characterize the affinity for binding to the human SUR1 isoform. Methoxy-repaglinide induced a complete monophasic inhibition curve with a Hill coefficient close to 1 (1.03) yielding a dissociation constant (KD) of 83 nM and an IC50 of 163 nM. Insulin secretion experiments on isolated rat islets were performed to prove biological activity, which was determined to be in the same range as that of original repaglinide.

Background: Alterations in the brain serotonin (5-HT) system have been found in patients with depression. We used the selective 5-HT transporter site ligand [11C](+)McN5652 and positron emission tomography (PET) to examine the hypothesis that alterations in 5-HT transporter levels may be present in selected regions of the brain in depressed patients., Methods: Four drug free depressed patients and four healthy control subjects were studied using [11C](+)McN5652 and PET. The distribution volume (DV) ratio of the PET ligand in selected regions of interest (ROIs) compared to cerebellum were calculated for the ROIs., Results: Patients showed significantly larger DV ratios in the left frontal cortex (P=0.013) and right cingulate cortex (P=0.043) compared to control subjects., Limitation: The sample size was modest with gender differences between the subject groups. The PET agent, [11C](+)McN5652, may have a lower binding affinity for the 5-HT transporter in the cortical regions compared to other brain regions., Conclusion: These findings suggest that 5-HT transporter sites may be increased in the frontal and cingulate cortices of depressed patients. These alterations in 5-HT transporter sites may be of pathophysiologic significance in the etiology of depression and its treatment.