Abstract
Adolescents are especially prone to drug addiction, but the underlying biological basis of their increased vulnerability remains unknown. We reveal that translational control by phosphorylation of the translation initiation factor eIF2α (p-eIF2α) accounts for adolescent hypersensitivity to cocaine. In adolescent (but not adult) mice, a low dose of cocaine reduced p-eIF2α in the ventral tegmental area (VTA), potentiated synaptic inputs to VTA dopaminergic neurons, and induced drug-reinforced behavior. Like adolescents, adult mice with reduced p-eIF2α-mediated translational control were more susceptible to cocaine-induced synaptic potentiation and behavior. Conversely, like adults, adolescent mice with increased p-eIF2α became more resistant to cocaine's effects. Accordingly, metabotropic glutamate receptor-mediated long-term depression (mGluR-LTD)-whose disruption is postulated to increase vulnerability to drug addiction-was impaired in both adolescent mice and adult mice with reduced p-eIF2α mediated translation. Thus, during addiction, cocaine hijacks translational control by p-eIF2α, initiating synaptic potentiation and addiction-related behaviors. These insights may hold promise for new treatments for addiction.
Highlights
In humans, adolescence is a period of heightened susceptibility to drug addiction (Chambers et al, 2003; Kandel et al, 1992)
Adolescence is a period of heightened susceptibility to drug addiction (Chambers et al, 2003; Kandel et al, 1992), but little is known about the underlying biological mechanisms
Changes in gene expression in key reward areas have been shown to play a critical role in drug-induced changes in synaptic potentiation and reward-related behavior (Hyman et al, 2006; Robison and Nestler, 2011)
Summary
Adolescence is a period of heightened susceptibility to drug addiction (Chambers et al, 2003; Kandel et al, 1992). Some molecular and cellular adaptations associated with drug use have been identified (Bowers et al, 2010; Luscher and Malenka, 2011), the biological basis of heightened vulnerability to substance abuse during adolescence remains elusive. Converging evidence supports the notion that addictive drugs hijack the cellular and molecular mechanisms underlying long-term changes in synaptic strength in the mesocorticolimbic dopamine (DA) system (including the ventral tegmental area (VTA), a key brain reward area implicated in the development of addiction (Kauer, 2004)) in a way that reinforces drug-seeking behavior An explanation for why young people are vulnerable to the effects of addictive substances remains elusive
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