Early life exposure to nicotine alters neurons, predisposes brain to addiction later

ScienceDaily | 5/21/2019 | Staff
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A UC San Diego School of Medicine team of scientists, headed by senior author Davide Dulcis, PhD, associate professor in the Department of Psychiatry, with colleagues at Veterans Affairs San Diego Healthcare System and Michigan State University, found that exposure to nicotine in the first few weeks of life (through maternal lactation) induced a variety of long-term neurological changes in young mice.

Specifically, it caused a form of neuroplasticity that resulted in increased numbers of modified neurons in the ventral tagmental area (VTA) of the brain following nicotine re-exposure as adults. These neurons displayed a different biochemistry than other neurons, including greater receptivity to nicotine and a greater likelihood of subsequent addictive behavior.

Studies - Smoking - Postnatal - Exposure - Children

"Previous studies have already shown that maternal smoking and early postnatal exposure to nicotine are associated with altered children's behaviors and an increased propensity for drug abuse in humans," said Dulcis. "This new research in mice helps elucidate the mechanisms of how and why. Neonatal nicotine exposure primes VTA neurons for a fate they normally would not have taken, making them more susceptible to the effects of nicotine when the animals are again exposed to nicotine later in life."

When young neurons are exposed to a foreign drug, such as nicotine, they create a molecular "memory," said first author Ben Romoli, PhD, a postdoctoral fellow in the Dulcis' lab. By increasing the expression of nicotine receptors and the molecular marker Nurr1, a protein that is normally found only in dopaminergic neurons, these GABA- and Glutamate-expressing neurons acquire the "readiness" to switch to a dopaminergic program when properly motivated by nicotine in the adult.

Animals - Adulthood - Fraction - Neurons - Reward

"We found that when the same animals are exposed to nicotine in adulthood, a fraction of these 'primed' glutamatergic neurons in the reward center begins to express genes required to produce dopamine. More dopamine in...
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