Understand the Brain Chemistry


By combining approaches of neuroscience and physics, mathematics and computing, a group of researchers and students from the UNAM explores the fine mechanisms of release of serotonin, essential for neurotransmitter rule of behavior, emotions, sleep, appetite and sex drive. The arrival of an electrical desire to the sites of connection between neurons causes the release of chemical neurotransmitters.

In addition, serotonin and other neurotransmitters can be released from several neuronal sites and reach distant points so that the responses of entire sets of these change over long periods. The quantitative study dynamics of vesicle fusion during exocytosis serotonin is part of a multidisciplinary project coordinated by Francisco Fernandez de Miguel at the Institute of Cellular Physiology (IFC) of the National University.

brain chemistry

Guillermo Ramirez Santiago and his students of the Institute of Physics (IF) of the UNAM have analyzed the experimental information of the laboratory of Miguel Fernandez by molecular diffusion models to understand the release of serotonin. In the Leech, the Anatomists from the 19th century have observed an invertebrate nervous system whose role neurophysiologists have questioned intensely since 1960.

Fine mechanisms

The study of neurons in the leech has generated the greatest quantity of knowledge about the fine mechanisms of serotonin release. The models developed by the group of Santiago Ramirez consider this to be out of the vesicles by diffusion, advection, or electro-diffusion. In humans, 90 percent is in the gastrointestinal tract; the rest is synthesized in serotonergic neurons of the nervous system. Its functions include the rule of behavior, emotional state, sleep, appetite and sex drive.

In particular, depression has been associated with lower levels in the nervous system, explained Ramirez Santiago. Why university researchers used leech neurons? First, because their physiology is similar to human and second because of their nervous scheme has few large neurons making them accessible to scientific experimentation.

Third, because of the 400 that exist in each of the 21 intermediate nodes nervous, seven are serotonergic system and their form, function, position, connections and contributions to behavior, has identified almost all. Finally, because of contrast, mammals have around 400,000 neurons that secrete serotonin, depending on class.


The process of exocytosis is a cellular transduction occurred in all eukaryotic cells. In response to certain stimuli, the membrane vesicle and the cell melt and produce a pore through which initiates the release of the contents to the outside of the cell membrane. The vesicles are filled with neurotransmitters, peptides, or hormones “he said. How exocytosis of serotonin occurs? Leech neurons keyed up by applying an electrical stimulus, which releases stored in vesicles.

Once that happens, each vesicle is recycled, ie back into the cell for serotonin refilled, which results in a cyclical process. It is possible to detect the release referred by their chemical properties: oxidation. In experimental conditions may favor this process, wherein four electrons per molecule are released. Thus, oxidation of the set of molecules produces an electric current whose strength is of the order of pico-amperes (9.10 amperes). Is detected with a carbon electrode located at a relatively short coldness, on the order of 40 nanometers from the outer mouth of the pore.

The long-term goal of the project, in which the IFC, the IF and the Faculty of Medicine, UNAM involved, is to better understand the molecular processes involved in the release to generate knowledge to design more efficient drugs, and the basis molecular exocytosis. The human body is a complex system in which the cells forming tissues and organs communicate with each other by biochemical and electrical signals consisting of a transportation of molecules that define intricate pathways of cell intercommunication.

One of the current challenges and the coming decades is to understand, from a molecular point of view (qualitative and quantitative), how cell-signaling processes occur. This will be possible to design drugs at the molecular level to correct the malfunction of the corresponding cell transduction pathway.