RATS WHO ARE given alcohol for ten days prior to being given cocaine already exhibit cocaine addicted behaviour.
This is includes continuing to seek cocaine despite receiving a brief electric shock when they did so, a new study from Columbia University Medical Centre reports.
Results suggest alcohol increases compulsive cocaine use by promoting the breakdown of important proteins in the nucleus accumbens, a brain region critical for reward-based memory.
Edmund Griffin Jr and colleagues evaluated cocaine-seeking behaviours of rats that had been given alcohol for ten days prior to cocaine administration compared to rats without prior alcohol exposure, as well as rats given alcohol and cocaine concurrently.
The rats with longer-term prior alcohol exposure were more persistent in seeking cocaine. For example, those rats pressed a lever to release cocaine an average of 58 times during a period of the experiment when no drugs were released; rats without alcohol exposure pressed the lever 18 times.
While addiction to cocaine is commonly preceded by use of other substances such as alcohol, nicotine and marijuana, the biological mechanisms by which these “gateway drugs” contribute to cocaine addiction are only beginning to be understood.
Since only a fraction (about 21%) of cocaine users progress to compulsive use, it is thought that both genetic and environmental factors are involved in vulnerability to cocaine addiction.
Griffin Jr told the science news website Inverse that the research further raises the question about whether that vulnerability is societal or genetic.
“The mechanism was always a big question of social vs biological.”
He says some scientists think it depends on whether a potential user is hanging out with people who use drugs, while others think some people are genetically predisposed to drug use.
The researchers also found that alcohol promoted the degradation of two proteins – histone deacetylases 4 and 5 – in the rats’ brains. Breakdown of these proteins creates a permissive environment for cocaine-induced gene expression, they report.
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