Dopamine receptors can be quantified using PET scans. For cannabis researchers this is tremendous news. A pair of studies demonstrate how stressful environments decrease the dopamine receptors of songbirds, while the other clarifies marijuana’s effects on dopamine release, PTSD and depression:
19-JUL-2019 – Louisiana State University Department of Biological Sciences Assistant Professor Christine Lattin, and colleagues conducted this study of wild songbirds showing that dopamine is important in responding to chronic stressors, which can help wildlife conservation efforts in response to environmental stressors such as habitat destruction, natural disasters, extreme weather events and increases in predation. […]
They found that one type of dopamine receptor decreased over time during captivity, which suggests that birds became less resilient to stress over time. The greater the decrease in dopamine receptors, the more they exhibited anxiety-related behaviors such as feather ruffling. All of the wild birds also decreased body mass.
“These physiological, neurobiological and behavioral changes suggest that songbirds are not able to habituate to captivity, at least over short periods of time. It is very important that scientists studying stress in wildlife find more ways to study them in their natural habitat,” Lattin said. […]
In a previous study, marijuana’s endocannabinoids were shown to affect the firing of dopamine neurons. University of Maryland School of Medicine scientists revealed the process:
…dopamine causally drives animals to avoid unpleasant or painful situations and stimuli. The results greatly expand the role that dopamine plays in driving behavior.
The researchers also examined the role that endocannabinoids play in this process. Endocannabinoids, brain chemicals that resemble the active ingredients in marijuana, play key roles in many brain processes. Here, Dr. Joseph F. Cheer and his colleagues found that endocannabinoids essentially open the gate that allows the dopamine neurons to fire. When the researchers reduced the level of endocannabinoids, the animals were much less likely to move to avoid shocks.
In both depression and PTSD, doctors already sometimes treat patients with medicine to increase dopamine and there are now clinical trials testing use of endocannabinoid drugs to treat these conditions. Dr. Cheer suggests that this approach may need to be used more often and should certainly be studied in more detail.
Dr. Cheer argues that the research sheds light on brain disorders such as post-traumatic stress disorder and depression. In depression, patients feel unable to avoid a sense of helplessness in the face of problems, and tend to ruminate rather than act to improve their situation. In PTSD, patients are unable to avoid an overwhelming sense of fear and anxiety in the face of seemingly low-stress situations. Both disorders, he says, may involve abnormally low levels of dopamine, and may be seen on some level as a failure of the avoidance system. […]
About 34% of medicinal cannabis use is directed at treating depression. For many patients marijuana reduces the anxiety and emotional pain that form links in the chain to their illnesses. The current findings raise another possibility, and not just for house sparrows (Passer domesticus). Cannabis may be the treatment of choice for people arrested and confined in cages for consuming marijuana or any other illicit drug.