Purkinje Neurons, The Enigmatic Cells Of The Cerebellum And The Heart

Viewed under the microscope, Purkinje neurons look like little Christmas trees. Neuroscience experts define them as a challenge and a mystery. It is known, for example, that they are in the cerebellum and also in our heart, and that according to several very recent studies they could have some kind of link with the appearance of autism spectrum disorder (ASD).

The neurological universe is almost as fascinating as the cosmos itself. Seen through a lens, these types of cells are not only striking because of their striking shape and large size. Purkinje neurons, in turn, receive up to ten times more connections than any other type of neuron.

Scientists have been looking to these types of structures for years because, unlike other inhibitory neurons, they also have the ability to “turn off” the functioning of other cells outside the cerebellum. Its electrophysiological activity is so unique that it opens the door to the possibility of developing new treatments and approaches for various conditions.

However, it takes time. Thus, universities, such as Tokyo, have been carrying out studies and observations at the laboratory level with zebrafish for years, trying to understand many of its functions, as well as its possible implication in the development of certain neurological disorders.

So let’s try to learn more about the interesting Purkinje neurons.

Purkinje neurons: what are they and where are they

Purkinje neurons are a type of brain cell of the GABAaergic type (that is, they have inhibitory functions). There are about 30 million of these neurons in the cerebellum and as many in the heart muscle. Thus, and thanks to the large number of Purkinje fibers existing in the heart muscle, the electrical impulse is also produced and transmitted.

Its discoverer was Jan Evangelista Purkyně. He was a neurologist at the University of Breslau, Prussia, who in 1832 was able to observe them for the first time using a type of achromatic microscope. Five years later, he would present his find to the scientific community in former Bohemia, now the Czech Republic.

Years later, Camillo Golgi, from the University of Pavia, in Italy, examined Purkinje cells by staining them with silver nitrate, trying to understand a little more about how they work. Also Santiago Ramón y Cajal, from the University of Barcelona, ​​would carry out his own research. It was in 1906 that both scientists received the Nobel Prize in Medicine for their contribution to understanding the structure of the nervous system.

As they are?

As we have already noted, Purkinje cells are inhibitory neurons. We also know that they are very large and that they receive a large number of connections. Dr. Thomas Launey, director of the molecular research unit at the Riken Institute in Japan, is one of the leading experts on these brain structures.

• As he himself explains in different works, they are tree-shaped, with highly branched dendrites and a single axon from which to send electrical impulses.
• Each cell body has a diameter of about eighty microns. It also has a very strong potential to inhibit excitatory neurons in the spinal cord.
• One of its main characteristics is that it can “turn off” other neurons that are outside the cerebellar cortex.
• On the other hand, it should be noted that there are two types of Purkinje neurons : mossy cells (which come from the brain stem) and climbing cells (which rise from the brainstem).

Purkinje neurons and their inhibitory functions

Purkinje cells are involved in motor processes and also in learning. We cannot ignore the large number of discoveries that are being made in recent years about the functions of the cerebellum, where these cells will undoubtedly be of key importance.

• Most Purkinje cells release a neurotransmitter called GABA (gamma-aminobutyric acid), which exerts inhibitory actions on other neurons. In this way, nerve impulses are reduced to be able, in this way, to regulate and coordinate our motor movements.
• This electrophysiological regulation is achieved in two ways. It can do so through its simple dendrites (or spikes), which exert an electrical activity that ranges from 17 to 150 Hz. Likewise, it can also activate a more intense type of electrical impulse that would have a potential between 1 and 3 Hz.

• Finally, it is interesting to know that they also facilitate concentration during learning processes.

Purkinje cells and autism

In early 2018, the journal  Molecular Psychiatry published an interesting study carried out at Harvard Medical University. According to this work, a dysfunction of the Purkinje cells of the cerebellum could mediate the onset of autism spectrum disorder (ASD). It is one more hypothesis that has been handled for a very short time.

The origin of this alteration would be genetic and would receive the name of tuberous sclerosis (TSC). It has been seen, for example, that many patients with autism have a very low level of this type of neurons. This leads to problems regulating behavior, movements, the constant hyperstimulation felt by these people, as well as the resulting social deficits.

Currently, work is being done on the production of Purkinje neurons from stem cells. A type of protein is also being designed that could help children reactivate the functionality and production of this important yet decisive type of structure. We will therefore be awaiting more data and information on a subject that, without a doubt, opens up multiple possibilities.