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Smoking remains the leading cause of preventable death in the United States, and early initiation is associated with greater difficulty quitting. Among adolescent smokers, those with attention-deficit hyperactivity disorder (ADHD), characterized by difficulties associated with impulsivity, hyperactivity, and inattention, smoke at nearly twice the rate of their peers.

Smoking remains the leading cause of preventable death in the United States, and early initiation is associated with greater difficulty quitting. Among adolescent smokers, those with attention-deficit hyperactivity disorder (ADHD), characterized by difficulties associated with impulsivity, hyperactivity, and inattention, smoke at nearly twice the rate of their peers. Although cigarette smoking is highly addictive, nicotine is a relatively weak primary reinforcer, spurring research on other potential targets that may maintain smoking, including the potential benefits of nicotine on attention, inhibition, and reinforcer efficacy. The present study employs the most prevalent rodent model of ADHD, the spontaneously hypertensive rat (SHR) and its control comparison Wistar Kyoto (WKY) to examine the effects of acute and chronic subcutaneous nicotine injections on performance in three operant response inhibition paradigms. Functional activation in select regions of the prefrontal cortex and striatum was also explored. Acute (0.1, 0.3, 0.6 mg/kg) and chronic (0.3 mg/kg) nicotine increased impulsive responding regardless of strain, dose, or operant schedule. Dose-dependent decreases in latency to initiate the task were also observed. SHR receiving daily nicotine injections showed less activation in the nucleus accumbens shell compared to saline controls. Despite close similarities, one of the three operant tasks did not detect response inhibition deficits in SHR relative to WKY. A closer examination of these tasks may highlight critical components involved in the amelioration of response inhibition deficits.
ContributorsMazur, Gabriel Joseph (Author) / Sanabria, Federico (Thesis advisor) / Killeen, Peter R (Committee member) / Neisewander, Janet L (Committee member) / Wynne, Clive DL (Committee member) / Arizona State University (Publisher)
Created2014
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Description
Nicotine is thought to underlie the reinforcing and dependence-producing effects of tobacco-containing products. Nicotine supports self-administration in rodents, although measures of its reinforcing effects are often confounded by procedures that are used to facilitate acquisition, such as food restriction, prior reinforcement training, or response-contingent co-delivery of a naturally reinforcing light.

Nicotine is thought to underlie the reinforcing and dependence-producing effects of tobacco-containing products. Nicotine supports self-administration in rodents, although measures of its reinforcing effects are often confounded by procedures that are used to facilitate acquisition, such as food restriction, prior reinforcement training, or response-contingent co-delivery of a naturally reinforcing light. This study examined whether rats acquire nicotine self-administration in the absence of these facilitators. A new mathematical modeling procedure was used to define the criterion for acquisition and to determine dose-dependent differences in rate and asymptote levels of intake. Rats were trained across 20 daily 2-h sessions occurring 6 days/week in chambers equipped with active and inactive levers. Each active lever press resulted in nicotine reinforcement (0, 0.015, 0.03, 0.06 mg/kg, IV) and retraction of both levers for a 20-s time out, whereas inactive lever presses had no consequences. Acquisition was defined by the best fit of a logistic function (i.e., S-shaped) versus a constant function (i.e., flat line) for reinforcers obtained across sessions using a corrected Akaike information criterion (AICc) as a model selection tool. The results showed an inverted-U shaped function for dose in relation to the percentage of animals that acquired nicotine self-administration, with 46% acquiring at 0.015 mg/kg, 73% at 0.03 mg/kg, and 58% at 0.06 mg/kg. All saline rats failed to acquire as expected. For rats that acquired nicotine self-administration, multiple model comparisons demonstrated that the asymptote (highest number of reinforcers/session) and half learning point (h; session during which half the assymptote had been achieved) were justified as free parameters of the reinforcers/session function, indicating that these parameters vary with nicotine dose. Asymptote exhibited an inverted U-shaped function across doses and half learning point exhibited a negative relationship to dose (i.e., the higher the dose the fewer sessions to reach h). These findings suggest that some rats acquire nicotine self-administration without using procedures that confound measures of acquisition rate. Furthermore, the modeling approach provides a new way of defining acquisition of drug self-administration that takes advantage of using all data generated from individual subjects and is less arbitrary than some criteria that are currently used.
ContributorsCole, Natalie (Author) / Neisewander, Janet L (Thesis advisor) / Sanabria, Federico (Thesis advisor) / Bimonte-Nelson, Heather A. (Committee member) / Olive, Michael F (Committee member) / Arizona State University (Publisher)
Created2011
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Description
The capability of cocaine-associated stimuli in eliciting craving in human addicts, even after extended periods of abstinence, is modeled in animals using cue reinstatement of extinguished cocaine-seeking behavior. This study aimed to examine brain activation in response to cocaine cues in this model apart from activation produced by test novelty

The capability of cocaine-associated stimuli in eliciting craving in human addicts, even after extended periods of abstinence, is modeled in animals using cue reinstatement of extinguished cocaine-seeking behavior. This study aimed to examine brain activation in response to cocaine cues in this model apart from activation produced by test novelty using a novel cue control. Rats trained to self-administer cocaine paired with either an oscillating light or tone cue underwent daily extinction training and were then tested for reinstatement of extinguished cocaine-seeking behavior elicited by response-contingent presentations of either their assigned cocaine-paired cue or the alternate, novel cue. Additional controls received saline infusions and cue presentations yoked to a cocaine-trained rat. Brains were harvested for Fos immunohistochemistry immediately after the 90-min reinstatement test. Surprisingly, conditioned and novel cues both reinstated responding to a similar degree; however magnitude of reinstatement did vary by cue modality with the greatest reinstatement to the light cues. In most brain regions, Fos expression was enhanced in rats with a history of cocaine training regardless of cue type with the exception of the Cg1 region of the anterior cingulate cortex, which was sensitive to test cue modality. Also Fos expression within the dorsomedial caudate-putamen was correlated with responding in the novel, but not conditioned, cue groups. In subsequent experiments, we observed a similar pattern of reinstatement in rats trained and tested for sucrose-seeking behavior, whereas rats trained and tested with the cues only reinstated to a novel light and tone, but not a familiar cue. The results suggest that novel cues reinstate responding to a similar extent as conditioned cues regardless of whether animals have a history of operant-delivered drug or a natural reinforcer. Furthermore, similar brain circuits as those involved in cocaine-seeking behavior are activated by novel cues, suggesting converging processes exist to drive conditioned and novel reinforcement seeking.
ContributorsBastle, Ryan (Author) / Neisewander, Janet L (Thesis advisor) / Sanabria, Federico (Committee member) / Olive, Michael F (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Nicotine self-administration is associated with decreased expression of the glial glutamate transporter 1 (GLT-1) and the cystine-glutamate exchange protein xCT in the nucleus accumbens core (NAcore). N-acetylcysteine (NAC), which is an antioxidant, anti-inflammatory, and glutamatergic agent, restores these proteins associated with increased relapse vulnerability. However, the specific molecular mechanisms driving

Nicotine self-administration is associated with decreased expression of the glial glutamate transporter 1 (GLT-1) and the cystine-glutamate exchange protein xCT in the nucleus accumbens core (NAcore). N-acetylcysteine (NAC), which is an antioxidant, anti-inflammatory, and glutamatergic agent, restores these proteins associated with increased relapse vulnerability. However, the specific molecular mechanisms driving NAC inhibitory effects on cue-induced nicotine reinstatement are unknown. Thus, the present study assessed NAC’s effects on cue-induced nicotine reinstatement are dependent on NAcore GLT-1 expression. Here, rats were treated with NAC in combination with intra-NAcore vivo-morpholinos to examine the role of GLT-1 in NAC-mediated inhibition of cue-induced nicotine seeking. Subchronic NAC treatment attenuated cue-induced nicotine seeking in male rats and an antisense vivo-morpholino (AS) designed to selectively suppress GLT-1 expression in the NAcore blocked this effect. NAC treatment was also associated with an inhibition of pro-inflammatory tumor necrosis factor alpha (TNFα) expression in the NAcore. As well, GLT-1 AS markedly increased expression of CD40, a known marker of pro-inflammatory M1 activation of microglia and macrophages. To further examine whether NAC-induced decreases in nicotine seeking involve suppression of TNFα, we manipulated a downstream mediator of this pathway, nuclear factor kappa B (NF-kB). Considering the putative role of NF-κB in learning, memory, and synaptic plasticity, separate experiments were performed where rats were treated with herpes simplex virus (HSV) vectors designed to increase (HSV-IKKca) or decrease (HSV-IKKdn) NF-κB signaling through interactions with IκB Kinase (IKK). The goal was to examine the role of NF-κB signaling in mediating nicotine seeking behavior and if NF-κB signaling regulates GLT-1 expression. HSV-IKKdn alone and in combination with NAC inhibited cue-induced nicotine reinstatement, while HSV-IKKca blocked the attenuating effect of NAC on reinstatement. Interestingly, both HSV-IKKdn and HSV-IKKca, regardless of NAC treatment, inhibited GLT-1 expression. Taken together, these results suggest that while GLT-1 may be a conserved neurobiological substrate underlying relapse vulnerability across drugs of abuse, immunomodulatory mechanisms may regulate drug-induced alterations in glutamatergic plasticity that mediate cue-induced drug-seeking behavior through GLT-1-independent mechanisms.
ContributorsNamba, Mark Douglas (Author) / Gipson-Reichardt, Cassandra D (Thesis advisor) / Conrad, Cheryl D. (Committee member) / Neisewander, Janet L (Committee member) / Arizona State University (Publisher)
Created2019