Nanoplastics found to disrupt dopamine system and social adaptation

Tiny plastic particles, or nanoplastics, could significantly alter brain development and behavior, according to a new study on mice published in Neuroscience. Researchers found that these particles affect the dopamine system – a key player in motivation and mood – and impact social behaviors during critical stages of development.

Nanoplastics, which measure less than 1,000 nanometers, are an emerging environmental concern. They are small enough to penetrate biological barriers and have been found in human organs, raising questions about their potential health effects. Earlier studies linked nanoplastics to inflammation and neurotoxicity in animals, but little was known about their impacts upon development.

To address this, Na-Hyun Kim and colleagues from Daegu Catholic University in South Korea examined how nanoplastics affected mice at different life stages. Using a carefully controlled study, the team administered nanoplastics orally once daily to pregnant mice during gestation, as well as directly to their offspring at different developmental stages.

The researchers divided male offspring mice into groups exposed to nanoplastics during mid-gestation, late-gestation, postnatal, juvenile, adolescent, or adult stages. They conducted behavioral tests such as locomotion, social behavior, and nest-building. Brain activity was also measured in regions tied to dopamine.

Upon analysis, the results revealed that the timing of exposure played a crucial role in determining its effects.

Social behaviors were notably altered, particularly in mice exposed during late gestation and early adulthood. These groups showed reduced social familiarity and increased anxiety-like behaviors, such as freezing when exposed to new environments.

Additionally, neural activity in key dopamine-related brain areas, such as the prefrontal cortex and amygdala, was disrupted.

Meanwhile, mice exposed during mid-gestation showed reduced movement, and those exposed during adolescence had heightened neural activity but no significant behavioral changes.

Evidently, the study highlighted differences in vulnerability based on developmental stages. “Overall… neural function influenced by nanoplastic administration influences the neurodevelopmental period from prenatal to postnatal, and their effects are different according to the timing of nanoplastic administration,” Kim and colleagues concluded.

While the study provides important insights, it also has limitations. It focused solely on male mice, leaving questions about potential sex differences unanswered. Additionally, maternal stress due to nanoplastic exposure was not evaluated, which could influence offspring development.

Despite these caveats, the research underscores the growing need to address nanoplastic pollution. With evidence mounting about their effects on the brain, these particles could have far-reaching implications for human health. For now, the study raises an urgent question: How can we reduce exposure to these invisible but impactful pollutants?

The study, “Effect of Nanoplastic Intake on the Dopamine System During the Development of Male Mice,” was authored by Na-Hyun Kim, Hye-In Choo, and Young-A Lee.