0
0
A recent breakthrough in neuroscience sheds new light on how cannabis interacts with brain development, especially during critical growth phases in adolescence. Scientists have discovered that cannabis affects brain cells in a way that disrupts brain plasticity—the brain’s ability to adapt and change—by targeting a key receptor on brain cells known as the CB1 receptor. The findings, which focus on the role of these receptors in astrocytes (a type of brain cell), offer new insights into how early cannabis exposure may impact learning and memory, particularly in young adults.
The Role of Cannabinoid Receptors in the Brain
Cannabis exerts its effects through binding to the Cannabinoid Receptor 1 (CB1), one of the most abundant receptors in the brain. These receptors function like switches, regulating various biological processes by turning them on or off. For years, researchers believed that CB1 receptors were predominantly located on neurons, the brain’s primary nerve cells. However, recent research has identified a surprising new player: astrocytes, glial cells that provide essential support to neurons.
Astrocytes and Brain Plasticity
Astrocytes play a critical role in brain development, particularly in early life, and are integral to brain plasticity—the brain’s ability to reorganize itself by forming new neural connections. During childhood and adolescence, there are “critical periods” of heightened plasticity when the brain is especially receptive to environmental influences. These periods are essential for learning and development, and disruptions during these windows can have lasting effects.
Christiaan Levelt, Professor of Molecular and Cellular Mechanisms of Cortical Development and Plasticity at VU Amsterdam, explains the importance of these periods. “In earlier studies from the ’80s, researchers injected astrocytes from a kitten into the visual cortex of an older cat, opening the critical period once more and allowing the brain to reorganize. We also know that CB1 receptor expression in astrocytes decreases with age—could this be related to the brain’s ability to adapt during these periods?”
Investigating CB1 Receptors in Mice
To explore the role of CB1 receptors on astrocytes in brain development, the research team conducted experiments using a special mouse model. They selectively disabled CB1 receptors in either nerve cells or astrocytes to observe the effects on brain function. Their study focused on the visual cortex, the brain region responsible for processing visual information, and examined how the absence of CB1 receptors affected the brain’s inhibitory system, which regulates neural activity.
The findings were striking: when CB1 receptors on astrocytes were removed, the brain’s ability to adapt to changes during development was significantly impaired. This was not the case in mice with CB1 receptors disabled on nerve cells, suggesting that astrocytes, rather than neurons, are essential for this adaptability.
Implications for Cannabis and Brain Development
These findings may explain why cannabis use during adolescence, when the brain is still undergoing critical developmental stages, can have negative effects on cognitive function. Although research on the long-term effects of cannabis is still ongoing, evidence suggests that disrupting the CB1 receptor on astrocytes during these critical periods can hinder the brain’s ability to adjust, potentially affecting learning, memory, and other cognitive functions.
Dr. Rogier Min, a Visiting Fellow in Integrative Neurophysiology at Amsterdam UMC, highlights the significance of these findings. “Cannabis is often considered relatively safe, but our research indicates that it can impact brain development, particularly in younger individuals. The CB1 receptor on astrocytes plays an essential role in early brain development, and disrupting this process can hinder the brain’s ability to adapt,” he says.
This research underscores the need for caution when it comes to cannabis use in adolescents and young adults. While the long-term consequences of cannabis on the brain are not yet fully understood, these findings provide a clearer picture of how cannabis may alter brain development during critical periods, affecting the brain’s flexibility and adaptability.
The study, titled “Inhibitory maturation and ocular dominance plasticity in mouse visual cortex require astrocyte CB1 receptors,” was published on November 15, 2024, in iScience.
For more details, you can refer to the study: DOI: 10.1016/j.isci.2024.111410.
