[This article was published on Sep 3, 2009 in the Science section. © 2009 The Varsity. It may point to one of the mechanisms that also changes the brain to make porn use / frequent orgasm addictive.]
Switch protein in the brain can turn on drug-dependent response without drug exposure
by Andrew Rusk
A joint study by researchers at the University of Toronto and Brigham Young University has clarified the potential role of a naturally occurring protein in drug addiction.
Researchers found that injecting rats with Brain-Derived Neurotrophic Factor resulted in the display of drug-dependent behaviour without any exposure to opiates. Irrespective of the drug being taken, BDNF triggers the brain to form a habit or addiction. In addition to their psychotropic effects, all addictive substances release BDNF upon chronic use. Although opiate exposure was absent in these rats, the addiction trigger, BDNF, caused a shift from a dopamine-independent to a dopamine-dependent opiate reward system, thus mimicking an addictive state.
“This work may reveal a mechanism that underlies drug addiction,” says Hector Vargas Perez, a post-doctoral fellow with U of T’s Department of Molecular Genetics, “Our work suggests that BDNF is crucial for inducing a drug-dependent state, one important aspect of drug addiction.”
The study builds upon prior research linking chronic drug exposure with an increase in BDNF in the Ventral Tegmental Area of the brain. The VTA is a group of neurons near the midline of the midbrain. This area houses the mesocortocilimbic dopamine system, which is involved in cognition, motivation, drug addiction, and multiple psychiatric disorders.
Increased BDNF excites the neurons in the VTA, whose activity would otherwise be inhibited. This “switch” commonly occurs when people become dependent on drugs, and it triggers several behavioural responses such as psychomotor sensitization and cue-induced drug seeking.
The breakthrough in this study lies in being able to trigger this “switch” through the use of BDNF without exposure to opiates. It is part of a larger project in determining how the brain handles drug addiction.
“If we can understand how the brain’s circuitry changes in association with drug abuse, it could potentially suggest ways to medically counteract the effects of dependency,” says psychology Professor Scott Stevenson at BYU, who adds that this study suggests that inducing a drug-dependent state requires BDNF.
While using BDNF to treat human addiction is a long way off, Perez believes this study confirms that addiction is “something real that we can see.”
Perez is quick to add that BDNF in only one of many factors at play in the study of addiction, and in many ways it’s an enigma that is still difficult to understand.
Low levels of BDNF have also been linked to conditions including depression, schizophrenia, obsessive-compulsive disorder, Alzheimer’s disease, Huntington’s disease, Rett syndrome, dementia, and eating disorders such as anorexia nervosa and bulimia nervosa.