Teens exposed to nicotine at higher alcoholism risk: study

People exposed to nicotine during adolescence may drink more alcohol than those not exposed to the stimulant, a study has found.

Exposure to nicotine at a young age changes the neuronal circuitry in the brain's reward pathways, according to the research published in the journal Cell Reports.

"This work on adolescent rats is particularly important because in recent years nicotine vaping with electronic cigarettes has increased among high school and middle school students," said John Dani from the University of Pennsylvania in the US.

The researchers administered nicotine via daily injections to the animals during adolescence or adulthood, then measured alcohol self-administration after a delay, enabling the adolescent rats to reach adulthood.

The rats exposed to adolescent nicotine pushed a lever to obtain a slightly sweetened alcohol drink more often for a greater daily intake of ethanol compared to rats that did not experience nicotine or rats or that only experienced nicotine during adulthood.

The researchers found that adolescent, but not adult, nicotine exposure altered the function of the normally inhibitory midbrain circuitry mediated by the neurotransmitter, gamma-Aminobutyric acid (GABA).

Specific GABA signals that were normally inhibitory in response to alcohol began to shift toward excitatory.

By altering the midbrain "reward-mediating" circuitry of the brain, this shift in alcohol-induced GABA signalling led to a long-lasting enhancement of alcohol self-administration in rats that were given nicotine at a young age.

The long-term neuronal changes are caused by a decreasing function in a chloride transporter called KCC2 in rat midbrain neurons.

Specifically, they found that these neurons less efficiently regulated chloride movement across the outer cell membrane, and this basic function altered alcohol's influence over the midbrain reward center.