Propensity toward relapse is a hallmark feature of addiction. Hence, understanding the cellular mechanisms responsible for relapse vulnerability represents an important focus of addiction research. One significant and long-lasting cellular adaptation observed in response to multiple drugs of abuse is downregulation of astroglial glutamate transporter GLT-1. However, relatively very little is known about how drug self-administration affects astrocytes beyond GLT-1 expression, or how astrocytes may contribute to mechanisms of drug seeking. Results collected during the preceding K99/R00 award indicate that restored expression of GLT-1 is pivotal to the mechanism of action of multiple compounds that reduce behavioral measures of relapse in the rat self- administration and reinstatement model of addiction. Preliminary data also indicate that downregulation of GLT-1 by cocaine is accompanied by reduced expression of glial fibrillary acidic protein (GFAP) and a retraction of astrocytes in the nucleus accumbens core. Astrocyte retraction is characterized by decreased surface area, volume, and decreased synaptic contacts. This finding represents a heretofore-unappreciated fundamental consequence of cocaine use on astrocyte cell biology. Thus, decreased GLT-1 expression is a component of larger-scale adaptions in astrocyte biology that occur following chronic cocaine use. These findings have led to the hypothesis that astrocyte retraction in the nucleus accumbens of cocaine-withdrawn rats contributes to synaptic adaptations that drive cocaine seeking. In order to test this hypothesis, the specific goals of this proposal are: (1) to determine when during the addiction cycle the morphological effects on astrocytes are induced (2) to determine the functional relationship between astrocyte retraction and synaptic adaptations believed to underlie cocaine seeking, and (3) to determine the relationship between astrocyte retraction and drug seeking after cessation of drug use. These questions will be addressed by combining rat cocaine self-administration with behavioral measures of cocaine seeking, high-resolution imaging of fluorescently labeled astrocytes, and whole cell patch-clamp electrophysiology. These studies will provide novel insight into how cocaine-dependent adaptations in astrocyte dynamics contribute to the cellular and behavioral pathologies characteristic of psychostimulant addiction. These studies will also provide important information toward the translational potential of astrocytes as a pharmacotherapeutic target for substance use disorders.

Public Health Relevance

The considerable public health burden of psychostimulant addiction creates a priority for intervention. Recent studies indicate that the cellular effects of cocaine use include astrocytes and neuron-astrocyte communication within the brain?s reward circuitry. This proposal seeks to determine how long-lasting cocaine-dependent adaptations in astrocyte structure and function mediate drug seeking, and to establish avenues for therapeutic intervention indicated by these adaptations.

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA041455-02
Application #
9293285
Study Section
Molecular Neuropharmacology and Signaling Study Section (MNPS)
Program Officer
Sorensen, Roger
Project Start
2016-06-15
Project End
2021-03-31
Budget Start
2017-04-01
Budget End
2018-03-31
Support Year
2
Fiscal Year
2017
Total Cost
$303,199
Indirect Cost
$100,699
Name
University of North Carolina Chapel Hill
Department
Psychology
Type
Schools of Arts and Sciences
DUNS #
608195277
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Kim, Ronald; Healey, Kati L; Sepulveda-Orengo, Marian T et al. (2018) Astroglial correlates of neuropsychiatric disease: From astrocytopathy to astrogliosis. Prog Neuropsychopharmacol Biol Psychiatry 87:126-146
Sepulveda-Orengo, Marian T; Healey, Kati L; Kim, Ronald et al. (2018) Riluzole Impairs Cocaine Reinstatement and Restores Adaptations in Intrinsic Excitability and GLT-1 Expression. Neuropsychopharmacology 43:1212-1223
Testen, Anze; Sepulveda-Orengo, Marian T; Gaines, Christiann H et al. (2018) Region-Specific Reductions in Morphometric Properties and Synaptic Colocalization of Astrocytes Following Cocaine Self-Administration and Extinction. Front Cell Neurosci 12:246
Kim, Ronald; Sepulveda-Orengo, Marian T; Healey, Kati L et al. (2018) Regulation of glutamate transporter 1 (GLT-1) gene expression by cocaine self-administration and withdrawal. Neuropharmacology 128:1-10
LaCrosse, Amber L; O'Donovan, Sinead M; Sepulveda-Orengo, Marian T et al. (2017) Contrasting the Role of xCT and GLT-1 Upregulation in the Ability of Ceftriaxone to Attenuate the Cue-Induced Reinstatement of Cocaine Seeking and Normalize AMPA Receptor Subunit Expression. J Neurosci 37:5809-5821