Abstract
1209
Objectives Microdialysis has been used to demonstrate that cocaine produces an increase in extracellular dopamine (DA) in the striatum of rats[1]. The present study sought to measure the same phenomenon with 11C-raclopride and small animal PET, and attempted to detect possible biases in PET-based measures of DA release based on timing differences in cocaine administration[4,5].
Methods PET images were acquired in 9 cocaine-naïve male Wistar rats. Rats received 3 bolus 11C-raclopride scans (1 rest and 2 cocaine). Scans were performed on IndyPETIII (~ 1 mm FWHM in-plane). Prior to each scan, rats were anesthetized with 0.1ml/100g ketamine/xylazine cocktail IM and secured on a stereotaxic holder. Animals received 2.0mg/kg cocaine IV 10 minutes (early cocaine) or 25 minutes (late cocaine) after tracer injection. Time activity curves were extracted from the striatum and cerebellum and binding potential (BP) was calculated by a Logan reference technique[2,3].
Results Taking early and late scans together, cocaine decreased BP from rest by 6.8 ± 3.8% (mean ± SEM) (n=18, p<0.03). Early cocaine decreased BP from rest by 5.9 ± 6.0% (n=9, p<0.14), and late cocaine decreased BP from rest by 7.7% ± 5.0% (n=9, p<0.07) but these two BP changes were not statistically different.
Conclusions Cocaine administered IV to anesthetized rats causes sufficient release of striatal DA to be detectable as a decrease in 11C-raclopride BP via small animal PET. No bias was observed in measured BP decrease with time of injection. Variability in our measurements may be too great to detect such biases.
Research Support R21 AA015077
- © 2009 by Society of Nuclear Medicine