Published 17 October 2017
THC restricts synaptic recovery
In their experiments, the researchers injected THC into the young mice, focusing on its effect on the GABA cells in the VTA. The team noted that just one THC injection did not have a significant impact on the functioning of GABA cells. But administering multiple injections — one injection of THC per day for 7 to 10 consecutive days — blocked a function called "synaptic recovery" in the GABA cells of the mice's brains.
Dr. Edwards explained to MNT that "all psychoactive substances that alter synaptic plasticity [...] of VTA dopamine cells, even once the drug is out of the system, are addictive, while non-addictive psychoactive substances do not alter plasticity. Therefore, we attempted chronic THC injections and noted that synaptic plasticity (long-term depression) was occluded."
The cumulative effect of repeated THC absorption in the brains of the young mice was to impact how GABA nerve cells normally function, leading to a dysregulation of dopamine levels.
Since dopamine "motivates" us to keep engaging in certain behaviors — such as eating or sexual intercourse — by rendering them pleasurable, if this neurotransmitter is not properly regulated, it could lead to addiction.
'Negative impact of THC on adolescents'
This could explain why marijuana use disorder is so common among consumers in the U.S., where almost 6 million people experienced it in 2016 alone, according to the National Institutes of Health (NIH).
Dr. Edwards explained that he saw clinical potential in the study's findings, and he said that his team's reasearch could offer new insight into mechanisms of addiction and withdrawal.
"It is important to note," he explained, "that these studies were carried out in juvenile/adolescent aged mice. This is important as adolescent humans have worse THC-induced outcomes compared to adults."
"[A]dolescents who use THC have decreased IQ, decreased cognition, and increased change of further drug abuse with other drugs," he said