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

Neonatal exposure to nicotine alters the reward circuity in the brains of newborn mice, increasing their preference for the drug in later adulthood, report researchers at University of California San Diego School of Medicine in a study published “in press” April 24, 2019 in Biological Psychiatry.

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.

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A new target for marijuana

Cellular-level changes to a part of the brain’s reward system induced by chronic exposure to the psychoactive component of marijuana may contribute to the drug’s pleasurable and potentially addictive qualities, suggests a study in young mice published in JNeurosci. The results could advance our understanding of marijuana’s effects on the developing brain as the drug’s rapidly changing legal status increases its recreational and medical use in the United States.

Drugs of abuse impact the ventral tegmental area (VTA) of the brain, which is rich in dopamine neurons. Using juvenile and adolescent mice, Jeffrey Edwards and colleagues investigated the effects of tetrahydrocannabinol (THC), the chemical in marijuana responsible for its effects on cognition and behavior, on VTA GABA cells, an understudied inhibitory cell type in the reward system that regulates dopamine levels.

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