The potential of a radiosensitive intracerebral probe to monitor 18F-MPPF binding in mouse hippocampus in vivo.
As mouse imaging has become more challenging in preclinical research, efforts have been made to develop dedicated PET systems. Although these systems are currently used for the study of physiopathologic murine models, they present some drawbacks for brain studies, including a low temporal resolution that limits the pharmacokinetic study of radiotracers. The aim of this study was to demonstrate the ability of a radiosensitive intracerebral probe to measure the binding of a radiotracer in the mouse brain in vivo.


METHODS
The potential of a probe 0.25 mm in diameter for pharmacokinetic studies was assessed. First, Monte Carlo simulations followed by experimental studies were used to evaluate the detection volume and sensitivity of the probe and its adequacy for the size of loci in the mouse brain. Second, ex vivo autoradiography of 5-hydroxytryptamine receptor 1A (5-HT(1A)) receptors in the mouse brain was performed with the PET radiotracer 2'-methoxyphenyl-(N-2'-pyridinyl)-p-(18)F-fluorobenzamidoethylpiperazine ((18)F-MPPF). Finally, the binding kinetics of (18)F-MPPF were measured in vivo in both the hippocampus and the cerebellum of mice.


RESULTS
Both the simulations and the experimental studies demonstrated the feasibility of using small probes to measure radioactive concentrations in specific regions of the mouse brain. Ex vivo autoradiography showed a heterogeneous distribution of (18)F-MPPF consistent with the known distribution of 5-HT(1A) in the mouse brain. Finally, the time-activity curves obtained in vivo were reproducible and validated the capacity of the new probe to accurately measure (18)F-MPPF kinetics in the mouse hippocampus.


CONCLUSIONS
Our results demonstrate the ability of the tested radiosensitive intracerebral probe to monitor binding of PET radiotracers in anesthetized mice in vivo, with high temporal resolution suited for compartmental modeling.
IMNC, UMR8165 CNRS-Université of Paris 7 and Paris 11, Orsay, France.
Aurélie
A
Desbrée
Mathieu
M
Verdurand
Jeremy
J
Godart
Albertine
A
Dubois
Roland
R
Mastrippolito
Frédéric
F
Pain
Laurent
L
Pinot
Thierry
T
Delzescaux
Hirac
H
Gurden
Luc
L
Zimmer
Philippe
P
Lanièce
D000818:Animals; D002531:Cerebellum / Q000000981:diagnostic imaging* / Q000378:metabolism; D003198:Computer Simulation; D005462:Fluorine Radioisotopes / Q000493:pharmacokinetics; D006624:Hippocampus / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D051379:Mice; D009010:Monte Carlo Method; D010879:Piperazines / Q000493:pharmacokinetics*; D049268:Positron-Emission Tomography; D011725:Pyridines / Q000493:pharmacokinetics*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*
D005462:Fluorine Radioisotopes; D010879:Piperazines; D011725:Pyridines; D019275:Radiopharmaceuticals; D044282:Receptor, Serotonin, 5-HT1A; C416325:4-(2'-methoxyphenyl)-1-(2'-(N-2'-pyridinyl)-p-(18F)fluorobenzamido )ethylpiperazine