Glutamatergic plasticity and alcohol dependence-induced alterations in reward, affect and cognition.
BACKGROUND
Alcohol dependence is characterized by a reduction in reward threshold, development of a negative affective state, and significant cognitive impairments. Dependence-induced glutamatergic neuroadaptations in the neurocircuitry mediating reward, affect and cognitive function are thought to underlie the neural mechanism for these alterations. These changes serve to promote increased craving for alcohol and facilitate the development of maladaptive behaviors that promote relapse to alcohol drinking during periods of abstinence.


OBJECTIVE
To review the extant literature on the effects of chronic alcohol exposure on glutamatergic neurotransmission and its impact on reward, affect and cognition.


RESULTS
Evidence from a diverse set of studies demonstrates significant enhancement of glutamatergic activity following chronic alcohol exposure. In particular, up-regulation of GluN2B-containing NMDA receptor expression and function is a commonly observed phenomenon that likely reflects activity-dependent adaptive homeostatic plasticity. However, this observation as well as other glutamatergic neuroadaptations are often circuit and cell-type specific.


CONCLUSIONS
Dependence-induced alterations in glutamate signaling contribute to many of the symptoms experienced in addicted individuals and can persist well into abstinence. This suggests that they play an important role in the development of behaviors that increase the probability for relapse. As our understanding of the complexity of the neurocircuitry involved in the addictive process has advanced, it has become increasingly clear that investigations of cell-type and circuit-specific effects are required to gain a more comprehensive understanding of the glutamatergic adaptations and their functional consequences in alcohol addiction.


CONCLUSIONS
While pharmacological treatments for alcohol dependence and relapse targeting the glutamatergic system have shown great promise in preclinical models, more research is needed to uncover novel, possibly circuit-specific, therapeutic targets that exhibit improved efficacy and reduced side effects.
Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425. Electronic address: burnete@musc.edu.
Elizabeth J
EJ
Burnett
Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425.
L Judson
LJ
Chandler
Department of Neuroscience, Medical University of South Carolina, Charleston, SC 29425.
Heather
H
Trantham-Davidson
D000339:Affect / Q000187:drug effects / Q000502:physiology; D000437:Alcoholism / Q000503:physiopathology* / Q000523:psychology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000503:physiopathology*; D003071:Cognition / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D012201:Reward
D018698:Glutamic Acid
Addiction; Glutamate; Negative affect; Plasticity; Relapse; Withdrawal