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Comparative Study
. 2011 Dec;65(12):1344-9.
doi: 10.1002/syn.20970.

Imaging of dopamine D2/3 agonist binding in cocaine dependence: a [11C]NPA positron emission tomography study

Rajesh Narendran  1 , Diana Martinez, Neale Scott Mason, Brian J Lopresti, Michael L Himes, Chi-Min Chen, Maureen A May, Julie C Price, Chester A Mathis, W Gordon Frankle
Affiliations
Comparative Study

Imaging of dopamine D2/3 agonist binding in cocaine dependence: a [11C]NPA positron emission tomography study

Rajesh Narendran et al. Synapse. 2011 Dec.

Abstract

Objective: Positron emission tomography (PET) studies performed with [(11) C]raclopride have consistently reported lower binding to D(2/3) receptors and lower amphetamine-induced dopamine (DA) release in cocaine abusers relative to healthy controls. A limitation of these studies that were performed with D(2/3) antagonist radiotracers such as [(11) C]raclopride is the failure to provide information that is specific to D(2/3) receptors configured in a state of high affinity for the agonists (i.e., D(2/3) receptors coupled to G-proteins, D(2/3 HIGH) ). As the endogenous agonist DA binds with preference to D(2/3 HIGH) relative to D(2/3 LOW) receptors (i.e., D(2/3) receptors uncoupled to G-proteins) it is critical to understand the in vivo status of D(2/3 HIGH) receptors in cocaine dependence. Thus, we measured the available fraction of D(2/3) (HIGH) receptors in 10 recently abstinent cocaine abusers (CD) and matched healthy controls (HC) with the D(2/3) antagonist and agonist PET radiotracers [(11) C]raclopride and [(11) C]NPA.

Methods: [(11) C]raclopride and [(11) C]NPA binding potential (BP) (BP(ND) ) in the striatum were measured with kinetic analysis using the arterial input function. The available fraction of D(2/3 HIGH) receptors, i.e., % R(HIGH) available = D(2/3 HIGH) /(D(2/3 HIGH) + D(2/3 LOW) ) was then computed as the ratio of [(11) C]NPA BP(ND) /[(11) C]raclopride BP(ND) .

Results: No differences in striatal [(11) C]NPA BP(ND) (HC = 1.00 ± 0.17; CD = 0.97 ± 0.17, P = 0.67) or available % R(HIGH) (HC = 39% ± 5%; CD = 41% ± 5%, P = 0.50) was observed between cocaine abusers and matched controls.

Conclusions: The results of this [(11) C]NPA PET study do not support alterations in D(2/3 HIGH) binding in the striatum in cocaine dependence.

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Conflict of interest statement

DISCLOSURES

The authors report no competing interests

Figures

Figure 1
Figure 1
Shows no significant difference between controls (white bars) and cocaine abusers (black bars) in the available fraction of D2/3 high receptors (% RHIGH) in the striatal subdivisions.
See this image and copyright information in PMC

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