n, probably via microglial activation.
The antibiotic minocycline reduces microglial activation. It would be interesting to see if minocycline might have antidepressant effects in people with depression symptoms and elevated translocator protein binding.
Depression and bipolar disorder have been linked to high levels of inflammatory proteins in the blood (namely CRP, IL-1, IL-6, and TNF-alpha), but the relationship between these illnesses and inflammation in the brain has not been well-characterized.
At the 2015 meeting of the Society for Biological Psychiatry, researcher Ghanshyan Pandey discussed findings from autopsy studies of people who died with a diagnosis of unipolar depression or bipolar disorder, and teens who died of suicide. The studies compare data from these ill people with those of controls who are matched for demographic characteristics.
Pandey found that the brains of those who died of unipolar depression and bipolar disorder showed more signs of inflammation compared to the controls. This included elevated levels of the inflammatory proteins IL-1B, IL-6, and TNF-alpha, in addition to elevated levels of the mRNA that leads to their production. Pandey also found that those with depression and bipolar disorder had higher levels of mRNA for the receptors to which TNF-alpha and other inflammatory proteins attach themselves.
Pandey performed similar autopsy studies of teens who died of suicide, the second leading cause of death for this age group, compared to teens who died of other causes. There were more signs of inflammation in the prefrontal cortices of teens who died of suicide. These included mRNA and proteins for IL-1B and TNF-alpha, and IL-6 proteins. In contrast to the ill adults, the teens who died of suicide had lower levels of the receptors for inflammatory proteins than controls. Another type of receptor known as toll-like receptors was higher in the ill teens, particularly the mRNA and proteins TLR3 and TLR4.
George Koob, Director of the National Institute on Alcohol Abuse and Alcoholism, discussed the neuroscience of chronic drug use at the 2015 meeting of the Society of Biological Psychiatry. His basic message was that chronic drug use is associated with A) loss of the reward value of the drug and B) a progressive increase in dysphoria and stress when off the drug. Both factors drive craving and drug seeking.
Access to high as opposed to moderate doses of a drug lead to an escalation in drug intake, and associated persistent increases in withdrawal dysphoria, which Koob called “the dark side.”
Koob explained that a month of detoxification is not sufficient, and that people quitting a drug need more time to let dopamine increase and to let levels of corticotropin releasing factor (CRF), which drives the anxiety and dysphoria of withdrawal, normalize. He stressed that for people addicted to opiates, it is important to taper levels of the drug to minimize withdrawal symptoms.
In addition to CRF, dynorphin also plays a role in chronic drug abuse. This opiate peptide acts at kappa opiate receptors and is associated with anxiety, dysphoria, and psychosis as opposed to morphine, which acts at mu opiate receptors and is associated with euphoria and decreased pain. Koob found that administration of the kappa opiate antagonist norbinaltorphimine (nor-BNI) blocks dose escalation of methamphetamine and brings abstinence-related compulsive drug seeking back to baseline.
At the 2015 meeting of the Society of Biological Psychiatry, Bruce McEwen, professor of neuroscience at Rockefeller University, gave an overview of stress’s effect on the brain. He explained that “chronic stress makes you stupid,” and said that while one can compensate for the effects of chronic stress, one cannot reverse them.
Short-term stress can be helpful, increasing cortisol, with generally positive effects. When stress lasts longer, the chronic increase in cortisol starts to cause problems: impaired memory, endangered neurons, decreased bone and muscle, and metabolic abnormalities.
McEwen said that chronic stress shrinks the dendrite