Effect of a history of major depressive disorder on smoking-induced dopamine release.

Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, California 90095, USA.
Biological psychiatry (Impact Factor: 8.93). 07/2009; 66(9):898-901. DOI: 10.1016/j.biopsych.2009.06.011
Source: PubMed

ABSTRACT Dopamine (DA) system dysfunction is implicated in the pathophysiology of major depressive disorder (MDD). We sought to determine if cigarette smokers with a history of MDD and current mild depressive symptoms have abnormal smoking-induced DA release (measured indirectly as change in (11)C-raclopride binding potential [BP(ND)]).
Fifty-six cigarette smokers either with (n = 10) or without (n = 46) a history of MDD (MDD+ and MDD-, respectively) underwent bolus-plus-continuous-infusion (11)C-raclopride positron emission tomography, during which they smoked a regular cigarette. Presmoking to postsmoking changes in (11)C-raclopride BP(ND) were compared between groups. Also, correlations were determined between change in BP(ND) and depression, anxiety, and withdrawal rating scale scores for the MDD+ group.
The MDD+ group had a significantly greater reduction in (11)C-raclopride BP(ND) (-16.3%) than the MDD- group (-8.4%) (analysis of covariance [ANCOVA], p = .03). Significant negative correlations were found between depression/anxiety and change in (11)C-raclopride BP(ND) (r = -.77, p < .01 and r = -.74, p = .01, respectively).
MDD+ smokers have greater smoking-induced DA release than MDD- smokers, and higher depression/anxiety levels are associated with greater smoking-induced DA release. These findings support the theory that MDD+ smokers have DA system dysfunction, including heightened smoking-induced DA release.

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    ABSTRACT: The radiotracer [(11)C]PHNO may have advantages over other dopamine (DA) D2/D3 receptor ligands because, as an agonist, it measures high-affinity, functionally active D2/D3 receptors, whereas the traditionally used radiotracer [(11)C]raclopride measures both high- and low-affinity receptors. Our aim was to take advantage of the strength of [(11)C]PHNO for measuring the small DA signal induced by nicotine, which has been difficult to measure in preclinical and clinical neuroimaging studies. Nicotine- and amphetamine-induced DA release in non-human primates was measured with [(11)C]PHNO and [(11)C]raclopride positron emission tomography (PET) imaging. Seven adult rhesus monkeys were imaged on a FOCUS 220 PET scanner after injection of a bolus of [(11)C]PHNO or [(11)C]raclopride in three conditions: baseline; preinjection of nicotine (0.1 mg/kg bolus+0.08 mg/kg infusion over 30 min); preinjection of amphetamine (0.4 mg/kg, 5 min before radiotracer injection). DA release was measured as change in binding potential (BPND). Nicotine significantly decreased BPND in the caudate (7±8%), the nucleus accumbens (10±7%), and in the globus pallidus (13±15%) measured with [(11)C]PHNO, but did not significantly decrease BPND in the putamen or the substantia nigra or in any region when measured with [(11)C]raclopride. Amphetamine significantly reduced BPND in all regions with both radiotracers. In the striatum, larger amphetamine-induced changes were detected with [(11)C]PHNO compared with [(11)C]raclopride (52-64% vs 33-35%, respectively). We confirmed that [(11)C]PHNO is more sensitive than [(11)C]raclopride to nicotine- and amphetamine-induced DA release. [(11)C]PHNO PET may be more sensitive to measuring tobacco smoking-induced DA release in human tobacco smokers.Neuropsychopharmacology advance online publication, 13 November 2013; doi:10.1038/npp.2013.286.
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    ABSTRACT: Conventional PET methods to estimate [(11)C]raclopride binding potential (BP ND) assume that endogenous dopamine concentration does not change during the scan time. However, this assumption is purposely violated in studies using pharmacological or behavioral stimuli to invoke acute dopamine release. When the assumption of steady-state dopamine is violated, conventional analysis methods may produce biased or even unusable estimates of BP ND. To illustrate this problem, we examined the effect of scan duration on ΔBP ND estimated by three common analysis methods (simplified reference tissue model, Logan graphical reference method, and equilibrium analysis) applied to simulated and experimental single-scan activation studies. The activation - dopamine release - in both the simulated and experimental studies was brief. Simulations showed ΔBP ND to be highly dependent on the window of data used to determine BP ND in the activation state. A similar pattern was seen in the data from human smoking studies. No such pattern of ΔBP ND dependence on the window of data used was apparent in simulations where dopamine was held constant. The dependence of ΔBP ND on the duration of data analyzed illustrates the inability of conventional methods to reliably quantify short-lived increases in endogenous dopamine.
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