A major challenge for the clinical treatment of cocaine addiction is the propensity for abstinent users to relapse upon re-exposure to environmental cues previously associated with cocaine. This vulnerability to relapse may increase after the acute drug withdrawal stage. Similarly, cue-induced cocaine seeking in rats intensifies or """"""""incubates"""""""" during the first months of withdrawal. This is mediated by an increase in GluA2-lacking, Ca2+ permeable (CP)-AMPARs in the nucleus accumbens (NAc). CP-AMPARs represent a very small percentage of the AMPARs in the NAc of drug-naive rats but accumulate in this region in association with the incubation of cue-induced seeking. These CP-AMPARs exhibit higher conductance than other AMPARs and are therefore likely to make NAc neurons more responsive to drug-related cues;in fact, blocking CP-AMPARs prevents the expression of incubated seeking. Thus, identifying the mechanism that leads to elevation of CP-AMPARs after cocaine withdrawal may help identify potential therapeutic targets for the treatment of cue-induced craving and relapse. In other brain regions, group I metabotropic glutamate receptor (mGluR) activation leads to the selective internalization of postsynaptic CP-AMPARs. While group I mGluRs do not seem to internalize AMPARs in the NAc, this has only been assessed in the NAc of drug-naive rodents, where CP-AMPAR levels are very low. Importantly, several studies report decreased group I mGluR levels in the NAc during withdrawal from repeated cocaine exposure. My central hypothesis is that group I mGluR activation selectively internalizes CP-AMPARs in the NAc and that CP-AMPARs accumulate during prolonged withdrawal from cocaine self- administration due to a decrease in group I mGluR levels in the NAc. I also hypothesize that group I mGluR activation in the NAc will prevent the expression of incubated cue-induced seeking by selectively internalizing CP-AMPARs in these cocaine-experienced rats.
Aim 1 will use cultured NAc neurons, which express CP- AMPARs, to test the working hypothesis that group I mGluR activation leads to the selective internalization of CP-AMPARs. Immunocytochemical experiments will determine if surface expression of CP-AMPARs is altered by acute and long-term group I mGluR activation or inhibition.
Aim 2 will test the working hypothesis that levels of group I mGluRs in the NAc decrease during prolonged withdrawal from extended access cocaine self- administration, and that pharmacological activation of NAc group I mGluRs in vivo reduces cue-induced cocaine seeking. Rats will self-administer cocaine or saline (controls) and biochemical studies will determine if group I mGluR surface, synaptic or extrasynaptic levels decrease in the NAc of """"""""incubated"""""""" rats. Behavioral studies will determine if acute intra-NAc injection of a group I mGluR agonist reduces incubated cue-induced cocaine seeking and internalizes CP-AMPARs. While these studies are underway, I will participate in a Training Plan that employs coursework, individual mentoring, and collaborative interactions to develop the non- bench skills needed to reach my goal of becoming a principal investigator in an academic setting.

Public Health Relevance

This proposal uses a rat model of addiction to study the cellular mechanisms that lead to intensification of cue- induced cocaine craving, a common trigger for relapse, after cocaine withdrawal. Our results may identify a molecular target (group I metabotropic glutamate receptors) for the development of medications to reduce cue- induced craving in abstinent cocaine addicts.

National Institute of Health (NIH)
National Institute on Drug Abuse (NIDA)
Postdoctoral Individual National Research Service Award (F32)
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Special Emphasis Panel (ZRG1-F02A-J (20))
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Avila, Albert
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Rosalind Franklin University
Schools of Medicine
North Chicago
United States
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Loweth, Jessica A; Scheyer, Andrew F; Milovanovic, Mike et al. (2014) Synaptic depression via mGluR1 positive allosteric modulation suppresses cue-induced cocaine craving. Nat Neurosci 17:73-80
Loweth, Jessica A; Tseng, Kuei Y; Wolf, Marina E (2014) Adaptations in AMPA receptor transmission in the nucleus accumbens contributing to incubation of cocaine craving. Neuropharmacology 76 Pt B:287-300
Reimers, Jeremy M; Loweth, Jessica A; Wolf, Marina E (2014) BDNF contributes to both rapid and homeostatic alterations in AMPA receptor surface expression in nucleus accumbens medium spiny neurons. Eur J Neurosci 39:1159-69
Plaza-Zabala, Ainhoa; Li, Xuan; Milovanovic, Mike et al. (2013) An investigation of interactions between hypocretin/orexin signaling and glutamate receptor surface expression in the rat nucleus accumbens under basal conditions and after cocaine exposure. Neurosci Lett 557 Pt B:101-6
Wang, Xiaoting; Cahill, Michael E; Werner, Craig T et al. (2013) Kalirin-7 mediates cocaine-induced AMPA receptor and spine plasticity, enabling incentive sensitization. J Neurosci 33:11012-22
Loweth, Jessica A; Tseng, Kuei Y; Wolf, Marina E (2013) Using metabotropic glutamate receptors to modulate cocaine's synaptic and behavioral effects: mGluR1 finds a niche. Curr Opin Neurobiol 23:500-6
Purgianto, Anthony; Scheyer, Andrew F; Loweth, Jessica A et al. (2013) Different adaptations in AMPA receptor transmission in the nucleus accumbens after short vs long access cocaine self-administration regimens. Neuropsychopharmacology 38:1789-97
Li, Xuan; DeJoseph, M R; Urban, Janice H et al. (2013) Different roles of BDNF in nucleus accumbens core versus shell during the incubation of cue-induced cocaine craving and its long-term maintenance. J Neurosci 33:1130-42
McCutcheon, James E; Loweth, Jessica A; Ford, Kerstin A et al. (2011) Group I mGluR activation reverses cocaine-induced accumulation of calcium-permeable AMPA receptors in nucleus accumbens synapses via a protein kinase C-dependent mechanism. J Neurosci 31:14536-41