Fourier Transform Coherent Anti-Stokes Raman Scattering Spectroscopy: A Comprehensive Review.

Fourier transform coherent anti-Stokes Raman scattering (FT-CARS) spectroscopy is a powerful spectroscopic method that combines the principles of Fourier transform spectroscopy with coherent anti-Stokes Raman scattering (CARS). This method stands out in spectroscopy for its ability to rapidly acquire coherent Raman spectra, achieving an impressive rate of over 10 000 spectra per second. The method involves scanning the optical delay between two femtosecond pulses; the initial pulse induces a vibrational coherence in the sample, while the subsequent pulse probes this coherence over increasing delays.

PET Imaging of VMAT2 with the Novel Radioligand [F]FE-DTBZ-d4 in Nonhuman Primates: Comparison with [C]DTBZ and [F]FE-DTBZ.

The vesicular monoamine transporter type 2 (VMAT2) is believed to be responsible for the uptake of monoamines into the vesicles of the synaptic terminals. Two VMAT2 radioligands [C]DTBZ and [F]FP-DTBZ have been used to assess the degree of nigrostriatal deficit in Parkinson's disease (PD) using positron emission tomography (PET). [F]FE-DTBZ-d4, the nondeuterated analogue of [F]FE-DTBZ showed similar imaging properties with better stability against defluorination.

A Nonhuman Primate PET Study: Measurement of Brain PDE4 Occupancy by Roflumilast Using (R)-[C]Rolipram.

Purpose: Phosphodiesterase 4 (PDE4) inhibition in the brain has been reported to improve cognitive function in animal models. Therefore, PDE4 inhibitors are one of key targets potential for drug development. Investigation of brain PDE4 occupancy would help to understand the effects of PDE4 inhibition to cognitive functions.

Development of [ Carbonyl-C]AZ13198083, a Novel Histamine Type-3 Receptor Radioligand with Favorable Kinetics.

The histamine subtype-3 receptor (HR) is implicated in a range of central nervous system disorders, and several radioligands have been developed for HR positron emission tomography imaging. However, a limitation of currently used PET radioligands for HR is the slow binding kinetics in high density brain regions. To address this, we herein report the development of three novel candidate HR radioligands, namely, [ carbonyl-C]AZ13153556 ([ carbonyl-C]4), [ carbonyl-C]AZD5213([ carbonyl-C]5), and [ carbonyl-C]AZ13198083 ([ carbonyl-C]6), and their subsequent preclinical evaluation in nonhuman primates (NHP).

Development of two fluorine-18 labeled PET radioligands targeting PDE10A and in vivo PET evaluation in nonhuman primates.

Introduction: Phosphodiesterase 10A (PDE10A) is a member of the PDE enzyme family that degrades cyclic adenosine and guanosine monophosphates (cAMP and cGMP). Based on the successful development of [C]T-773 as PDE10A positron emission tomography (PET) radioligand, in this study our aim was to develop and evaluate fluorine-18 analogs of [C]T-773.

Methods: [F]FM-T-773-d and [F]FE-T-773-d were synthesized from the same precursor used for C-labeling of T-773 in a two-step approach via F-fluoromethylation and F-fluoroethylation, respectively, using corresponding deuterated synthons.

Positron emission tomography measurement of brain MAO-B inhibition in patients with Alzheimer's disease and elderly controls after oral administration of sembragiline.

Purpose: In Alzheimer's disease (AD), increased metabolism of monoamines by monoamine oxidase type B (MAO-B) leads to the production of toxic reactive oxygen species (ROS), which are thought to contribute to disease pathogenesis. Inhibition of the MAO-B enzyme may restore brain levels of monoaminergic neurotransmitters, reduce the formation of toxic ROS and reduce neuroinflammation (reactive astrocytosis), potentially leading to neuroprotection. Sembragiline (also referred as RO4602522, RG1577 and EVT 302 in previous communications) is a potent, selective and reversible inhibitor of MAO-B developed as a potential treatment for AD.

Brain PET measurement of PDE10A occupancy by TAK-063, a new PDE10A inhibitor, using [11 C]T-773 in nonhuman primates.

Because phosphodiesterase 10A (PDE10A) degrades both cyclic adenosine monophosphate and cyclic guanosine monophosphate and is distributed mainly in the striatum, PDE10A inhibitors have been considered to potentially be useful therapeutic agents for psychiatric and neurodegenerative diseases such as schizophrenia and Huntington's disease. We measured striatal PDE10A occupancy by TAK-063, a newly developed compound with high affinity and selectivity for PDE10A, using PET with [(11)C]T-773 in nonhuman primates. Two 123-min dynamic PET measurements were performed on three female rhesus monkeys, once at baseline and again after intravenous administration of different doses of TAK-063 (0.

Discovery and Preclinical Validation of [(11)C]AZ13153556, a Novel Probe for the Histamine Type 3 Receptor.

Unlabelled: The histamine type 3 receptor (H3) is a G protein-coupled receptor implicated in several disorders of the central nervous system. Herein, we describe the radiolabeling and preclinical evaluation of a candidate radioligand for the H3 receptor, 4-(1S,2S)-2-(4-cyclobutylpiperazine-1-carbonyl)cyclopropyl]-N-methyl-benzamide (5), and its comparison with one of the frontrunner radioligands for H3 imaging, namely, GSK189254 (1). Compounds 1 and 5 were radiolabeled with tritium and carbon-11 for in vitro and in vivo imaging experiments.

Evaluation of a novel PDE10A PET radioligand, [(11) C]T-773, in nonhuman primates: brain and whole body PET and brain autoradiography.

Phosphodiesterase 10A (PDE10A) is considered to be a key target for the treatment of several neuropsychiatric diseases. The characteristics of [(11) C]T-773, a novel positron emission tomography (PET) radioligand with high binding affinity and selectivity for PDE10A, were evaluated in autoradiography and in nonhuman primate (NHP) PET. Brain PET measurements were performed under baseline conditions and after administration of a selective PDE10A inhibitor, MP-10.

Development of a series of novel carbon-11 labeled PDE10A inhibitors.

Phosphodiesterase 10A (PDE10A) is a member of the PDE family of enzymes that degrades cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Our aim was to label a series of structurally related PDE10A inhibitors with carbon-11 and evaluate them as potential positron emission tomography (PET) radioligands for PDE10A using nonhuman primates. The series consisted of seven compounds based on the 3-(1H-pyrazol-5-yl)pyridazin-4(1H)-one backbone.

Large Variation in Brain Exposure of Reference CNS Drugs: a PET Study in Nonhuman Primates.

Background: Positron emission tomography microdosing of radiolabeled drugs allows for noninvasive studies of organ exposure in vivo. The aim of the present study was to examine and compare the brain exposure of 12 commercially available CNS drugs and one non-CNS drug.

Methods: The drugs were radiolabeled with (11)C (t 1/2 = 20.

Quantitative Analysis of ¹⁸F-(E)-N-(3-Iodoprop-2-Enyl)-2β-Carbofluoroethoxy-3β-(4'-Methyl-Phenyl) Nortropane Binding to the Dopamine Transporter in Parkinson Disease.

Unlabelled: (18)F-(E)-N-(3-iodoprop-2-enyl)-2β-carbofluoroethoxy-3β-(4'-methyl-phenyl) nortropane ((18)F-FE-PE2I) is a recently developed radioligand for the in vivo quantification of the dopamine transporter (DAT) in the striatum and substantia nigra (SN). The aim of this study was to examine the suitability of (18)F-FE-PE2I as a tool for imaging the nigrostriatal pathway in Parkinson disease (PD) with PET.

Methods: Ten PD patients (9 men and 1 woman; mean age ± SD, 60 ± 9 y; Hoehn and Yahr, 1-2; Unified Parkinson Disease Rating Scale motor, 18.

Molecular Imaging of PDE10A Knockout Mice with a Novel PET Radiotracer: [(11)C]T-773.

Purpose: [(11)C]T-773 is a new radioligand for positron emission tomography (PET) targeting the phosphodiesterase 10A enzyme (PDE10A). PDE10A is highly expressed in the striatum by medium spiny neurons, and it has been demonstrated to be involved in the regulation of striatal signaling through the reduction of medium spiny neuronal sensitivity towards glutamatergic excitation. PDE10A is associated with Parkinson's disease and different neuropsychiatric disorders such as Huntington's disease, obsessive-compulsive disorders (OCD) and schizophrenia.

Amphetamine decreases α2C-adrenoceptor binding of [11C]ORM-13070: a PET study in the primate brain.

Background: The neurotransmitter norepinephrine has been implicated in psychiatric and neurodegenerative disorders. Examination of synaptic norepinephrine concentrations in the living brain may be possible with positron emission tomography (PET), but has been hampered by the lack of suitable radioligands.

Methods: We explored the use of the novel α2C-adrenoceptor antagonist PET tracer [(11)C]ORM-13070 for measurement of amphetamine-induced changes in synaptic norepinephrine.

Positron emission tomography imaging of the 18-kDa translocator protein (TSPO) with [18F]FEMPA in Alzheimer's disease patients and control subjects.

Purpose: Imaging of the 18-kDa translocator protein (TSPO) is a potential tool for examining microglial activation and neuroinflammation in early Alzheimer's disease (AD). [(18)F]FEMPA is a novel high-affinity second-generation TSPO radioligand that has displayed suitable pharmacokinetic properties in preclinical studies. The aims of this study were to quantify the binding of [(18)F]FEMPA to TSPO in AD patients and controls and to investigate whether higher [(18)F]FEMPA binding in AD patients than in controls could be detected in vivo.

Determination of plasma protein binding of positron emission tomography radioligands by high-performance frontal analysis.

Positron emission tomography (PET) is an imaging technique based on the use of radioligands labeled with short lived radionuclides, such as (11)C (t½=20.4min) and (18)F (t½=109.8min), which as a consequence often requires rapid plasma protein binding analysis methods.

(18)F-MCL-524, an (18)F-Labeled Dopamine D2 and D3 Receptor Agonist Sensitive to Dopamine: A Preliminary PET Study.

Unlabelled: PET has been used to examine changes in neurotransmitter concentrations in the living brain. Pioneering PET studies on the dopamine system have used D2 and D3 receptor (D2/D3) antagonists such as (11)C-raclopride. However, more recently developed agonist radioligands have shown enhanced sensitivity to endogenous dopamine.

Positron emission tomography imaging of 5-hydroxytryptamine1B receptors in Parkinson's disease.

Impairment of the central serotonin system in Parkinson's disease (PD) has been shown postmortem and in vivo with positron emission tomography (PET). The aim of this PET study was to examine and compare the availability of the 5-hydroxytryptamine (5-HT)(1B)-receptor subtype in patients with PD and age-matched control subjects. Twelve control subjects and 12 PD patients were examined with PET using the 5-HT(1B)-radioligand [(11)C]AZ10419369.

Synthesis, radiolabeling, and in vivo pharmacokinetic evaluation of the amyloid beta radioligand [11C]AZD4694 in nonhuman primates.

Purpose: [(18)F]AZD4694 (2-(2-(18)F-fluoro-6-(methylamino)-3-pyridyl)benzofuran-5-ol) is a radioligand suitable for imaging of amyloid beta deposits in the living human brain using positron emission tomography (PET). Here, we report the preparation and pharmacokinetic profile of its carbon-11 (t1/2 = 20.4 min) labeled isotopolog [(11)C]AZD4694 and compare [(11)C]AZD4694 with the hitherto most widely applied amyloid PET radioligand [(11)C]Pittsburgh Compound B (PiB).

Characterization of [(11)C]Cimbi-36 as an agonist PET radioligand for the 5-HT(2A) and 5-HT(2C) receptors in the nonhuman primate brain.

Only recently the first successful serotonin 2A (5-HT2A) receptor agonist PET radioligands have been described, with [(11)C]Cimbi-36 reported as the most promising in the pig brain so far. Agonist radioligands may target specifically the G protein-coupled state of the receptors and thereby provide a more meaningful assessment of available receptors than antagonist radioligands. In the current study we characterized [(11)C]Cimbi-36 receptor binding in the primate brain.

Simultaneous determination of protein-free and total positron emission tomography radioligand concentrations in plasma using high-performance frontal analysis followed by mixed micellar liquid chromatography: application to [11C]PBR28 in human plasma.

A two-dimensional liquid chromatographic (LC) system was developed for the determination of protein-free and total (free + bound forms) positron emission tomography (PET) radioligand concentrations in plasma by direct plasma injection. The unbound PET radioligand was first analyzed by high-performance frontal analysis using a short gel-filtration column and phosphate buffered saline solution as the mobile phase. All the collected effluent from the gel-filtration column was then transferred to the second dimension consisting of a monolithic C-18 column and mixed (anionic and nonionic surfactants) micellar eluent for determination of the total PET radioligand concentration.

Improved radiometabolite analysis procedure for positron emission tomography (PET) radioligands using a monolithic column coupled with direct injection micellar/high submicellar liquid chromatography.

A high-speed and high-sensitive direct plasma radiometabolite analysis method for positron emission tomography (PET) radioligands has been developed. It was based on micellar/high submicellar liquid chromatography (LC) using a semi-preparative alkyl-bonded silica rod column in conjunction with steep gradient and high flow rate for rapid macromolecule removal from plasma without significant sample preparation and fast/efficient separation of PET radioligands from their radiometabolites. Excellent separation of target PET radioligand from its radiometabolites was achieved within 4 min with a limit of detection of 1 Bq (Bq) level.

Improvement of brain uptake for in vivo PET imaging of astrocytic oxidative metabolism using benzyl [1-(11)C]acetate.

Brain uptake of acetate is insufficient for obtaining a quantitative image of astrocytic oxidative metabolism. To improve the brain uptake of [1-(11)C]acetate, we synthesized benzyl [1-(11)C]acetate ([1-(11)C]BA) and conducted a positron emission tomography (PET) study assessing astrocytic oxidative metabolism. The brain uptake of [1-(11)C]BA was markedly higher compared with [1-(11)C]acetate, and disappeared with a half-life of 20 min in all regions studied.

A simplified radiometabolite analysis procedure for PET radioligands using a solid phase extraction with micellar medium.

Unlabelled: A solid phase extraction method has been developed for simple and high-speed direct determination of PET radioligands in plasma.

Methods: This methodology makes use of a micellar medium and a solid-phase extraction cartridge for displacement of plasma protein bound radioligand and separation of PET radioligands from their radiometabolites without significant preparation. The plasma samples taken from monkey or human during PET measurements were mixed with a micellar eluent containing an anionic surfactant sodium dodecyl sulphate and loaded onto SPE cartridges.

"Mixed" anionic and non-ionic micellar liquid chromatography for high-speed radiometabolite analysis of positron emission tomography radioligands.

A mixed micellar liquid chromatographic (LC) method, the mobile phase consisting of anionic and non-ionic surfactants, has been developed for the high-speed direct radiometabolite analysis of positron emission tomography (PET) radioligands in plasma. The addition of Triton X-100 on an anionic surfactant sodium dodecyl sulphate (SDS) mobile phase improved elution strength and peak efficiency for many PET radioligands. Several radioligands could be easily separated from their radioactive metabolites with short run time of only 4 min using a "pure" (without organic solvent) mixed micellar mobile phase and semi-preparative monolithic C(18)-bonded silica column by simple isocratic elution without any treatment of plasma.