You may recall learning bits and pieces of ancient psychiatric history in some physiology or psychology course. I am referring to the four temperaments proposed by Galen who believed that four bodily fluids were uniquely responsible for some aspect of human behavior: blood, bile, black bile, and phlegm. After Galen, the medical and psychiatric community became cerebral-centric, believing that most aspects of human behavior manifested from operations of the brain and feedback with other parts of the body. The best example would be reflexes and muscle memory which don’t really require the brain but simply the spinal cord.
Thankfully, some scientists have reverted back to hypotheses proposed in ancient medical texts. The most recent incidence was this year when scientists in California did blood transfusions and gave mice systemic injections of another mouse’s blood to study whether biological factors in the blood control the rate of neurodegeneration. Ponce de Leon would have been proud.
In this study, the researchers created a parabiotic mouse which means that these researchers made a post-natal Siamese mouse for the purpose of having a young adult mouse share a circulatory system with an aged mouse. I can only imagine the amount of surgical skill that it requires to do this in a mouse! In a second set of experiments, aged mice were injected with the blood of young mice. In both cases of blood transfusion or systemic injection of plasma, the rate of neurodegeneration was slowed in aged mice that had been introduced to young adult blood. Nothing happened when aged blood was introduced into another aged mouse. Because of the journal in which the study was published in–Nature–it is no surprise that this protection from neurodegeneration was confirmed at many levels, behaviorally, electrophysiologically, histologically, and molecularly.
Moreover, the experimental design of this study has paved a path to investigate many other neurological events that may be controlled by biological factors circulating in the blood. Even Steven Colbert agrees. You know you’ve made it in science when your sh*t ends up on the Daily Show or Colbert Report to be poked fun of.
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Villeda, S., Plambeck, K., Middeldorp, J., Castellano, J., Mosher, K., Luo, J., Smith, L., Bieri, G., Lin, K., Berdnik, D., Wabl, R., Udeochu, J., Wheatley, E., Zou, B., Simmons, D., Xie, X., Longo, F., & Wyss-Coray, T. (2014). Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice Nature Medicine, 20 (6), 659-663 DOI: 10.1038/nm.3569