September 2015 In mice, a cocaine-induced imbalance in the activity of two key populations of neurons in the reward system persists for a longer period after repeated exposure to the drug. For long-term users, this change could both weaken the cocaine “high” and strengthen the compulsion to seek the drug.
Researchers monitored the activity of two types of neurons in mice: “urge” neurons, which promote feelings of reward and repeating behaviors that have produced rewards, and “control” neurons, which dampen those feelings and inhibit behavior.
January 2015 Dr. Paul E. M. Phillips spoke on “Phasic Dopamine Transmission During Substance Abuse,” describing investigations that he has led into the role of brief, seconds-long bursts of dopamine signaling in addictive processes. Dr. Rita Z. Goldstein spoke on “Targeting the Brain, Cognition, and Motivation for Intervention in Addiction.”
This study demonstrated that cocaine increases expression of the protein E2F3a in the brain’s reward system. The changes in E2F3a levels in the nucleus accumbens are tied to addiction-related behaviors and to altered gene expression.
June 2015 A stressed rat will seek a dose of cocaine that is too weak to motivate an unstressed rat. Researchers traced the physiological pathway that links stress and the stress hormone corticosterone to increased dopamine activity and heightened responsiveness to cocaine.