Comparison of intravenous and intraperitoneal [123I]IBZM injection for dopamine D2 receptor imaging in mice.
BACKGROUND
Intraperitoneal (IP) injection represents an attractive alternative route of radiotracer administration for small animal imaging, e.g., for longitudinal studies in transgenic mouse models. We explored the cerebral kinetics of the reversible dopamine D2 receptor ligand [(123)I]IBZM after IP injection in mice.


METHODS
Cerebral [(123)I]IBZM kinetics were assessed by ex vivo autoradiography in mice sacrificed between 30 and 200 min after IP or intravenous (IV) injection. The striatum-to-cerebellum (S/C) uptake ratio at 140 min was evaluated in wild-type mice and R6/2 transgenic mice (a Huntington's disease model) in comparison with in vitro autoradiography using [(3)H]raclopride.


RESULTS
[(123)I]IBZM uptake was slower and lower after IP injection [maximum uptake in striatum 5.6% injected dose per gram (ID/g) at 60 min] than IV injection (10.5%ID/g at 30 min). Between 60 and 120 min, striatal (cerebellar) uptake after IP injection reached 63% (91%) of the uptake after IV injection. The S/C uptake ratio increased to 15.5 at 200 min after IP injection, which corresponds to 87% of the IV injection value (17.8). Consistent with in vitro [(3)H]raclopride autoradiography, the S/C ratio given by ex vivo [(123)I]IBZM autoradiography (140 min after IP injection) was significantly reduced in R6/2 mice.


CONCLUSIONS
Although IP injection resulted in slower kinetics, relevant measures of dopamine D2 receptor availability were comparable. Thus, IP injection represents a promising route of tracer administration for small animal [(123)I]IBZM SPECT. This should considerably simplify the implementation of longitudinal small animal neuroimaging studies, e.g., in transgenic mouse models.
Meyer
Philipp T
PT
Department of Neurology, University Hospital Aachen, 52074 Aachen, Germany. pmeyer@ukaachen.de
Salber
Dagmar
D
Schiefer
Johannes
J
Cremer
Markus
M
Schaefer
Wolfgang M
WM
Kosinski
Christoph M
CM
Langen
Karl-Josef
KJ
D000818:Animals; D001345:Autoradiography; D001549:Benzamides / Q000008:administration & dosage* / Q000493:pharmacokinetics; D001921:Brain / Q000000981:diagnostic imaging; D001923:Brain Chemistry; D018492:Dopamine Antagonists; D006801:Humans; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011759:Pyrrolidines / Q000008:administration & dosage* / Q000493:pharmacokinetics; D020891:Raclopride; D019275:Radiopharmaceuticals / Q000008:administration & dosage* / Q000493:pharmacokinetics; D017448:Receptors, Dopamine D2 / Q000187:drug effects* / Q000235:genetics; D015899:Tomography, Emission-Computed, Single-Photon
D001549:Benzamides; D018492:Dopamine Antagonists; D011759:Pyrrolidines; D019275:Radiopharmaceuticals; D017448:Receptors, Dopamine D2; D020891:Raclopride; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide