Currently, when you want to investigate about mental disorders in animal experiments, mice are usually used genetically manipulated to produce these disorders, which is very invasive and, of course, harmful to these animals.
However, a recent discovery related to a curious fish opens the door to the possibility of investigating mental disorders without altering the genes of domestic species.
The case of the caveman fish without eyes
In nature we can find beings that fascinate the most curious and become the object of study by researchers who want to unravel all their secrets. A very specific case is the fish known as Mexican tetra (Astyanax mexicanus) .
This rare aquatic species has a special feature: it exists in two different forms, one with eyes and the other without them. The first form lives in rivers, while the other, besides being albino, lives in aquatic areas that are inside certain caves and their eye cells have been degraded over time to live in the dark, to save energy, so your study can reveal more data about which genes participate in the formation of the eyes.
And that's how Masato Yoshizawa (biologist at the University of Hawaii) and his team chose this animal to perform trials. The most surprising thing is that this animal could have more secrets, not only be a case of organ loss, but also become a good model for the study of mental illnesses in humans, such as autism or schizophrenia. Let's see how it happened.
The comparative study to understand mental disorders
Thanks to the existence of these two populations within the same species it has been possible to study their genetic code , making crossings between the two at the laboratory level, since reproduction between both is possible. In this process it is possible to quantify a characteristic and how it is distributed in their offspring, a technique used by Gregor Mendel, father of genetics, in his study of peas. To give an example, thanks to this it has been known that a mutation in a gene known as "cbsa" is responsible for a population that does not develop the eyes.
During their investigations, Yoshikawa and his collaborators contemplated that the two populations of tetra were not only differentiated by their physical appearance, but that there was also a great difference in their social behavior. Those who inhabit surface waters are sociable and even have a social structure between them. On the other hand, the cavemen are loners, in fact, they reject the company. In addition, they have symptoms of anxiety and hyperactivity and never sleep.
With this data in mind, in a first experiment, Yoshikawa crossed the populations again to see to what extent this difference in social behavior is genetically rooted or based on behaviors learned in a specific context.
Medicating the caveman fish
The results of their trials were presented at the 23rd International Conference on Underground Biology in Fayeteville, Arkansas. Yoshikawa says that 90% of the 101 classic genes that are related to the risk of developing mental illness in humans are present in the Mexican tetra genome. Data that could turn this animal into a new model for the study of these diseases.
But the thing does not end here, because with another trial he treated solitary fish with the antidepressant psychodrug Fluoxetine (also known by its trademark Prozac) in combination with the antipsychotic Clozapine, causing the fish to become sociable, lower their levels of anxiety, that they would swim less frequently and that they could sleep. With this, Yoshikawa's team wanted to demonstrate that these fish react in a similar way to how a human patient would.
The importance that you want to give with this finding is to have an animal that has "symptoms" that are present in autism or schizophrenia, such as the absence of sleep, hyperactivity or anxiety, and all this naturally.
There is still much to be done and more tests to be done, but for the moment the evidence indicates that the Mexican tetra fish can become a new tool to follow studies of psychic disorders, both at the genetic base level and in the investigation of new drugs. Even so, some experts emphasize that there is a limitation in this model, since it is a fish, since humans and fish are separated by 400 million years of evolution and the results can not be extrapolated so lightly.