Thursday, June 24, 2004
In this post, I review the recent news article, then discuss the broader scientific context to show why it is important. I then review some of the clinical applications of the basic science, including the role that the endogenous opiate system (and some other systems) may play is such conditions as addiction, eating disorders, and compulsive repetition of trauma.
Here is an excerpt of the article that inspired me to write this post:
Thursday, June 24, 2004
WASHINGTON (AP) - Newborn mice shriek frantically when mom's away - unless they have a defect in the same brain pathway that responds to morphine, says research that sheds new light on mother-infant bonding.
Beyond unraveling the biology of that most basic of bonds, the work also may offer new leads to better understand autism, a disorder characterized by poor social attachment, scientists from Italy's National Research Center report.
At issue is the brain's opioid system, best known for its role in pain, pleasure and addiction. Opioid drugs like morphine act on that system to block physical pain.
But there have long been clues that the pathway plays a role in some basic emotional pain, too, because giving morphine to animals can decrease their social behaviors.
Thus, one theory behind autism's symptom of social indifference is that the brain might be incapable of forming strong social bonds without feedback from its opioid reward system - like the pleasure a baby should feel from loving parental care.
To test that, Italian neuroscientist Francesca D'Amato and colleagues bred mice to lack a crucial opioid receptor in the brain, and compared them to normal baby mice.
First, they separated the newborns from their mothers for short periods. Normally that sparks nonstop shrieking from the babies. But the opioid-deficient pups hardly cried, the researchers report in Friday's edition of the journal Science.
And while normal mice babies always chose the nest built by their own mother over another mother's bed, only about a third of the opioid-deficient babies did. [...]
The researchers showed that mice who are lacking the gene needed to make a particular opiate receptor do not exhibit normal attachment behaviors. The receptor is the part of the nerve cell that detects the presence of the endogenous (coming from within) opiate, and causes the nerve cell to respond. For an introduction to the neurochemistry or receptors (and a lot more), you can download the primer, Brain Facts, from the Society for Neuroscience website. (The link takes you to the download page. The download itself is 984KB.)
The term opiate refers to a chemical that acts like morphine, which originally was derived from the opium poppy. The term endorphin refers chemicals, that are naturally found in the brain, that act like morphine. Endorphin is a portmanteau of endogenous and morphine. Opiates and endorphins are not the only brain chemicals that are involved in the attachment process.
Oxytocin and vasopressin are two hormones that are released in large quantities during childbirth. It has been postulated that they play a role in maternal-infant bonding. More specifically, they appear to heighten the acuity of memory to certain stimuli, such as the exact smell of the baby and the exact sound of its cry.
I remember when I was a fourth-year medical student, spending a month in a pediatric hospital, on a unit that cared for infants. Usually, there were 15 to 20 babies there at any time, and usually at least 5 or 6 were crying. As a result, there was a constant din of babies crying. It literally never stopped. Like a person living near the ocean, one soon learns to tune it out, at least on a conscious level. On an unconscious level, it still grates on the nerves.
From time to time, I would be talking with one of the mothers, out in the hallway. Invariably, within a few minutes, she would suddenly stop, hold up a finger, and say, "That one is mine." Somehow, she had discerned the sound of her own baby's cry out of the mind-numbing cacophony. I saw this dozens of times, and it amazed me every time. When I tell this to women who have had babies of their own, they just give me that pitiful "of course you don't understand, you're a man" look. It is true. I don't understand.
Back to the topic at hand. There is evidence for other brain chemicals playing a role in the attachment process. See this (45KB PDF) paper for a review.
Beyond the basic science, there is some clinical application to all of this. There is a pharmaceutical product, ReVia (naltrexone) blocks opiate receptors. It is used to help persons with chemical dependency refrain from using. It originally was marketed to help reduce craving for alcohol in alcoholics. It also has been used, with some success, for addiction to opiates such as heroin, Vicodin, etc.
Another clinical use for naltrexone is to reduce repetitive self-injury. Although no one really knows why some people cut or burn themselves over and over, the theory is that the self-injurious behavior causes the brain to release endorphins, and the experience of endorphin release rewards the behavior. For some people, naltrexone can help them stop hurting themselves. Likewise, naltrexone can reduce the frequency of gambling, and bingeing/purging (in patients with eating disorders).
Readers with an insatiable appetite for the clinical relevance of neurochemistry, especially as it relates to attachment, may want to read this article by the guru of PTSD, Bessel van der Kolk. The Compulsion to Repeat the Trauma is a pretty dense article about attachment gone awry. The basic idea is that people who have been traumatized form an attachment to the perpetrator of the trauma, and may even develop a tendency to do things to repeat the trauma. If you don't want to read the entire thing, here are the last two paragraphs:
Childhood abuse and neglect enhance long-term hyperarousal and decreased modulation of strong affect states. Abused children may require much higher external stimulation to affect the endogenous opioid system for soothing than when the biologic concomitants of comfort are easily activated by conditioned responses based on good early caregiving experiences. Victimized people may neutralize their hyperarousal by a variety of addictive behaviors, including compulsive re-exposure to victimization of self and others. Gaining control over one's current life, rather than repeating trauma in action, mood, or somatic states, is the goal of treatment. The only reason to uncover traumatic material is to gain conscious control over unbidden re-experiences or re-enactments. The presence of strong attachments provides people with the security necessary to explore their life experiences and to interrupt the inner or social isolation that keeps them stuck in repetitive patterns. In contrast with victimized children, adults can learn to protect themselves and make conscious choices about not engaging in relationships or behaviors that are harmful.
I think it is important to note that there is a lot of evidence that the neurochemistry of the endorphin system is involved in attachment, as well as in the response to trauma and the development of repetitive self-injurious behaviors. However, the way this actually works in humans is still speculative.
(Note: The Rest of the Story/Corpus Callosum has moved. Visit the new site here.)
E-mail a link that points to this post:
I know that many initial business contacts and business relationships form via the communication of 'sports information/trivia'. In fact, your knowledge of sports can well affect how you progress in a corporaton.
I've found this to be true. Now I question, 'why?' Why is so much money spent on moving sports information? Not just the construction of a basketball court, but an information infrastructure?
Is it solely due to the endorphin release on par of that from gambling? You emotionally invest, and in return you get an endorphin rush?
How much of the economy can be explained in just chemical terms?