Risk factors for developing addiction include structural abnormalities in cortical and subcortical regions and associated psychological traits. One such trait concerns the propensity for attribution of incentive salience to drug-associated cues, rendering such cues to be ?attractive? and ?magnetic? and capable of instigating drug- seeking behavior. Sign-tracking rats (STs) approach and contact a Pavlovian conditioned stimulus for food while their counterparts, the goal-trackers (GTs), also learn about predictive nature of such cues but they do not approach them. STs have been extensively demonstrated to be vulnerable for developing addiction-like behaviors and thus have been established as a major animal model of addiction vulnerability. Because impairments in attentional abnormalities are considered an essential component of psychological traits associated with addiction vulnerability, we demonstrated that STs exhibit relatively poor attentional performance that is mediated via low levels of cortical cholinergic neuromodulation. These behavioral and neurochemical characteristics of STs are consistent with the hypothesis that relatively low levels of cholinergic neuromodulation bias the subject away from goal-directed attention and toward cue-driven (or bottom-up) attention. We also showed that, in contrast to GTs, the presence of a Pavlovian cocaine cue fails to increase levels of cholinergic neuromodulation in STs, thereby fostering attention-capture by the cue and cue-directed behavior. The proposed research will first test the hypothesis that a failure of the neuronal choline transporter (CHT) to mobilize in response to stimulation of cholinergic neurons is a cellular mechanism accounting for the attenuated capacity for cholinergic neuromodulation in STs. Second, we will test the hypothesis that by experimentally attenuating CHT function and inhibiting basal forebrain cholinergic activity, sign-tracking behavior manifests and, in GTs, attentional control is diminished, and GTs are more likely to approach a classically conditioned cocaine cue. Third, based on evidence indicating that stimulation of ?4?2* nicotinic acetylcholine receptors (nAChRs) mediates effects of cholinergic neuromodulation on cortical circuitry, we will test the hypothesis that, in STs, such a treatment fosters goal-tracking, improves attentional control and reduces the degree to which a cocaine cue controls behavior. Together, this research will demonstrate that cholinergic-attentional deficits are essential components of addiction vulnerability traits, that a dysregulated CHT is a neuromarker of the trait indexed by sign-tracking, and that sign-tracking and associated vulnerabilities can be reversed by upregulating cholinergic neuromodulation of the cortex.
Structural brain abnormalities and associated psychological traits are increasingly considered risk factors contributing to the development of addiction. About a third of rats from outbred populations have a propensity to approach and contact cues associated with food or addictive drugs (?sign-trackers?); these rats more readily administer addictive drugs and exhibit relapse. This research will identify a new neuronal/cellular mechanism that is essential for developing sign-tracking behavior, mediates poor attentional control, and that enhances the power of drug-associated cues to control behavior.
