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1.
Mol Psychiatry ; 28(10): 4272-4279, 2023 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-37814129

RESUMEN

Selective serotonin reuptake inhibitors (SSRIs) are widely used for treating neuropsychiatric disorders. However, the exact mechanism of action and why effects can take several weeks to manifest is not clear. The hypothesis of neuroplasticity is supported by preclinical studies, but the evidence in humans is limited. Here, we investigate the effects of the SSRI escitalopram on presynaptic density as a proxy for synaptic plasticity. In a double-blind placebo-controlled study (NCT04239339), 32 healthy participants with no history of psychiatric or cognitive disorders were randomized to receive daily oral dosing of either 20 mg escitalopram (n = 17) or a placebo (n = 15). After an intervention period of 3-5 weeks, participants underwent a [11C]UCB-J PET scan (29 with full arterial input function) to quantify synaptic vesicle glycoprotein 2A (SV2A) density in the hippocampus and the neocortex. Whereas we find no statistically significant group difference in SV2A binding after an average of 29 (range: 24-38) days of intervention, our secondary analyses show a time-dependent effect of escitalopram on cerebral SV2A binding with positive associations between [11C]UCB-J binding and duration of escitalopram intervention. Our findings suggest that brain synaptic plasticity evolves over 3-5 weeks in healthy humans following daily intake of escitalopram. This is the first in vivo evidence to support the hypothesis of neuroplasticity as a mechanism of action for SSRIs in humans and it offers a plausible biological explanation for the delayed treatment response commonly observed in patients treated with SSRIs. While replication is warranted, these results have important implications for the design of future clinical studies investigating the neurobiological effects of SSRIs.


Asunto(s)
Disfunción Cognitiva , Inhibidores Selectivos de la Recaptación de Serotonina , Humanos , Inhibidores Selectivos de la Recaptación de Serotonina/farmacología , Escitalopram , Encéfalo , Sinapsis , Disfunción Cognitiva/tratamiento farmacológico , Citalopram/farmacología , Citalopram/uso terapéutico
2.
Bioorg Med Chem Lett ; 29(8): 986-990, 2019 04 15.
Artículo en Inglés | MEDLINE | ID: mdl-30795854

RESUMEN

Pretargeted nuclear imaging based on the ligation between tetrazines and nano-sized targeting agents functionalized with trans-cyclooctene (TCO) has recently been shown to improve both imaging contrast and dosimetry in nuclear imaging of nanomedicines. Herein, we describe the improved radiosynthesis of a 11C-labeled tetrazine ([11C]AE-1) and its preliminary evaluation in both mice and pigs. Pretargeted imaging in mice was carried out using both a new TCO-functionalized polyglutamic acid and a previously reported TCO-functionalized bisphosphonate system as targeting agents. Unfortunately, pretargeted imaging was not successful using these targeting agents in pair with [11C]AE-1. However, brain imaging in pig indicated that the tracer crossed the blood-brain-barrier. Hence, we suggest that this tetrazine scaffold could be used as a starting point for the development of pretargeted brain imaging, which has so far been a challenging task.


Asunto(s)
Radioisótopos de Carbono/química , Tomografía de Emisión de Positrones , Radiofármacos/química , Tetrazoles/química , Animales , Encéfalo/diagnóstico por imagen , Radioisótopos de Carbono/metabolismo , Difosfonatos/química , Marcaje Isotópico , Ratones , Neoplasias/diagnóstico por imagen , Ácido Poliglutámico/química , Radiofármacos/metabolismo , Porcinos , Tetrazoles/metabolismo , Distribución Tisular
3.
Chem Sci ; 12(35): 11668-11675, 2021 Sep 15.
Artículo en Inglés | MEDLINE | ID: mdl-34659701

RESUMEN

Pretargeted imaging can be used to visualize and quantify slow-accumulating targeting vectors with short-lived radionuclides such as fluorine-18 - the most popular clinically applied Positron Emission Tomography (PET) radionuclide. Pretargeting results in higher target-to-background ratios compared to conventional imaging approaches using long-lived radionuclides. Currently, the tetrazine ligation is the most popular bioorthogonal reaction for pretargeted imaging, but a direct 18F-labeling strategy for highly reactive tetrazines, which would be highly beneficial if not essential for clinical translation, has thus far not been reported. In this work, a simple, scalable and reliable direct 18F-labeling procedure has been developed. We initially studied the applicability of different leaving groups and labeling methods to develop this procedure. The copper-mediated 18F-labeling exploiting stannane precursors showed the most promising results. This approach was then successfully applied to a set of tetrazines, including highly reactive H-tetrazines, suitable for pretargeted PET imaging. The labeling succeeded in radiochemical yields (RCYs) of up to approx. 25%. The new procedure was then applied to develop a pretargeting tetrazine-based imaging agent. The tracer was synthesized in a satisfactory RCY of ca. 10%, with a molar activity of 134 ± 22 GBq µmol-1 and a radiochemical purity of >99%. Further evaluation showed that the tracer displayed favorable characteristics (target-to-background ratios and clearance) that may qualify it for future clinical translation.

4.
J Neurosci Methods ; 294: 51-58, 2018 01 15.
Artículo en Inglés | MEDLINE | ID: mdl-29146191

RESUMEN

BACKGROUND: The increasing use of the pig as a research model in neuroimaging requires standardized processing tools. For example, extraction of regional dynamic time series from brain PET images requires parcellation procedures that benefit from being automated. COMPARISON WITH EXISTING METHODS: Manual inter-modality spatial normalization to a MRI atlas is operator-dependent, time-consuming, and can be inaccurate with lack of cortical radiotracer binding or skull uptake. NEW METHOD: A parcellated PET template that allows for automatic spatial normalization to PET images of any radiotracer. RESULTS: MRI and [11C]Cimbi-36 PET scans obtained in sixteen pigs made the basis for the atlas. The high resolution MRI scans allowed for creation of an accurately averaged MRI template. By aligning the within-subject PET scans to their MRI counterparts, an averaged PET template was created in the same space. We developed an automatic procedure for spatial normalization of the averaged PET template to new PET images and hereby facilitated transfer of the atlas regional parcellation. Evaluation of the automatic spatial normalization procedure found the median voxel displacement to be 0.22±0.08mm using the MRI template with individual MRI images and 0.92±0.26mm using the PET template with individual [11C]Cimbi-36 PET images. We tested the automatic procedure by assessing eleven PET radiotracers with different kinetics and spatial distributions by using perfusion-weighted images of early PET time frames. CONCLUSION: We here present an automatic procedure for accurate and reproducible spatial normalization and parcellation of pig PET images of any radiotracer with reasonable blood-brain barrier penetration.


Asunto(s)
Mapeo Encefálico/métodos , Encéfalo/anatomía & histología , Encéfalo/metabolismo , Imagenología Tridimensional/métodos , Imagen por Resonancia Magnética , Tomografía de Emisión de Positrones , Animales , Atlas como Asunto , Radioisótopos de Carbono , Femenino , Radioisótopos de Flúor , Masculino , Procesamiento de Señales Asistido por Computador , Porcinos
5.
ACS Chem Neurosci ; 7(11): 1614-1619, 2016 11 16.
Artículo en Inglés | MEDLINE | ID: mdl-27564969

RESUMEN

The toxic hallucinogen 25B-NBOMe is very rapidly degraded by human liver microsomes and has low oral bioavailability. Herein we report on the synthesis, microsomal stability, and 5-HT2A/5-HT2C receptor profile of novel analogues of 25B-NBOMe modified at the primary site of metabolism. Although microsomal stability could be increased while maintaining potent 5-HT2 receptor agonist properties, all analogues had an intrinsic clearance above 1.3 L/kg/h predictive of high first-pass metabolism.


Asunto(s)
Fenetilaminas/farmacología , Fenetilaminas/farmacocinética , Agonistas del Receptor de Serotonina 5-HT2/farmacología , Agonistas del Receptor de Serotonina 5-HT2/farmacocinética , Anisoles/química , Línea Celular , Evaluación Preclínica de Medicamentos , Estabilidad de Medicamentos , Células HEK293 , Alucinógenos/química , Humanos , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Fenetilaminas/síntesis química , Fenetilaminas/química , Receptor de Serotonina 5-HT2A/genética , Receptor de Serotonina 5-HT2A/metabolismo , Receptor de Serotonina 5-HT2C/genética , Receptor de Serotonina 5-HT2C/metabolismo , Agonistas del Receptor de Serotonina 5-HT2/síntesis química , Estereoisomerismo , Relación Estructura-Actividad
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