The Use of HiSPECT to Investigate Dopaminergic Involvement in the Development of Stereotypic Behaviour

Abstract

Functional molecular imaging is becoming  increasingly popular for in vivo research on small  animals, because it has a number of scientific  advantages over ex vivo methods. The molecular  parameters themselves can be used in other areas  of investigation also, such as monitoring of the  dopaminergic and serotonergic involvement in  the development of stereotypic behaviour. In  Single Photon Emission Computed Tomography  (SPECT), a radioactive substance with specific  affinity for a certain molecular target is injected  intravenously and after a period of time the  radioactivity that is not washed out from the region  of interest, is measured. A relative measure of  quantification, i.e., the binding index (BI), can then  be calculated. This paper aims to introduce a broad  readership to one possible application of SPECT  by presenting preliminary data about the dopamine  transporter (DAT) status in the Mongolian gerbil  (Meriones unguiculatus). 99mTechnetium-labelled  Ethylcysteinate Dimer tracer (24.42 ± 5.92 MBq)  was injected in the femoral vein of four gerbils  to provide brain perfusion images that allow  anatomical identification of DAT-rich regions  that were imaged in another four gerbils using  123I-labelled FP-CIT tracer (44.33 ± 11.66 MBq).  Furthermore, the optimal scan time for FP-CIT  was established in one gerbil. The study was  successful in obtaining brain perfusion images as  well as demonstrating regional binding of FP-CIT  to the basal ganglia, DAT-rich areas in the brain.  The optimal scan time for DAT-imaging was 4 ½  hours. Our preliminary data suggest the Mongolian  gerbil is a suitable model for combining SPECT  and behavioural observations in the investigation  of stereotypic behaviour.