What is the preBötzinger Complex? Anatomy and functions

This part of the medulla oblongata helps us to breathe continuously and automatically.

As a general rule, an adult human being at rest breathes at a rate of twelve to eighteen breaths per minute. Breathing is essential for our survival, a process that we carry out in a semi-conscious way continuously throughout our lives.

But who makes sure we do it? What part of our organism causes us to carry out this basic function? The answer lies in the medulla oblongata, specifically in the preBötzinger complex..

The preBötzinger complex: description and basic localization

The preBötzinger complex is a set or network of neurons located in the spinal cord or medulla oblongataspecifically in its ventromedial part, forming part of the brainstem. This neuronal network appears in both hemispheres, being a bilateral and symmetrical structure. It is connected to the spinal cord, and as we have mentioned, it is fundamental for the generation and maintenance of the respiratory rhythm.

It is a structure located recently, specifically in 1991, and in it different types of neurons have been found that allow through their interaction the genesis and rhythmicity of the respiratory cycle. The preBötzinger complexes of both hemispheres seem to function partially independently, although they communicate in order to synchronize.

Main functions

Although this structure is still poorly understood, several important functions are attributed to it.

1. Basic respiratory rhythm

The preBötzinger complex is a fundamental element to keep us alive, and its injury may cause death due to respiratory depression. Its main function is the generation and management of the respiratory rhythm..

2. Matching respiration to environmental needs.

Interaction with other areas of the brain allows the preBötzinger complex to regulate the respiratory rhythm regulate the respiratory rhythm according to environmental needs.. For example, if we do sports, our breathing will accelerate.

3. Oxygen level uptake

It has been detected that this complex and its connections are able to detect and act according to the oxygen level in the organism. For example, if we are suffocating, it is frequent that our respiratory rhythm is acceleratedas the body seeks to acquire the oxygen it needs to survive.

An unknown mechanism of action

The way in which this structure functions is still not completely clear, but experiments with rodents have shown that it is linked to the neurokinin-1 hormone receptor and to the action of neurotransmitters.

The existence of "pacemaker" neurons has been observed (similar to what occurs with the cardiac rhythm), some of which are voltage-dependent and others voltage-independent. Their exact function is still debated, although it is speculated that the voltage-dependent ones are the most closely linked to the generation of the respiratory rhythm by allowing the emission of action potentials through the uptake of sodium.

In any case, the hypothesis the hypothesis with the greatest empirical support is the one that indicates that it is the action of the set of neurons and their interaction that allows the rhythm to be generated, being the result of the interaction and not the interaction of the neurons.being the result of the interaction and not of the activity of a single type of neuron.

Much more research is needed to know the exact functioning of this region, which is a field of study to be deepened.

Neurotransmitters involved

Regarding the neurotransmitters with the greatest effect in this area, it has been perceived that glutamatergic activity is essential for the pre-Bötzinger complex to act in order to allow respiration. Specifically, it is the activity of AMPA receptors that plays the most important role, although some participation of NMDA receptors in the process has also been observed (although in some studies the modification of NMDA did not generate real changes and they do not seem to be essential). Their inhibition can cause cessation of the respiratory rhythm, while the use of agonists causes an increase in the respiratory rhythm..

When it comes to reducing the respiratory rhythm, the neurotransmitters that seem to act the most are GABA and glycine.

In addition to the above, there are other neurotransmitters that influence the respiratory rhythm through this structure. Although they do not participate directly in the genesis of the respiratory rhythm, they do modulate it. Examples are serotonin, adenosine triphosphate or ATP, substance P, somatostatin, noradrenaline, opioids and acetylcholine. This is why many substances and drugs cause an alteration of the respiratory rhythm.

One aspect to take into account is that emotions also have an important effect on the respiratory rhythm, due to the effect on this area of the secreted neurotransmitters. For example, in the case of experiencing nervousness or anxiety, the respiratory rhythm increases, while in the case of despair and depression it tends to slow down.

Effects of the lesion of this area

Although the preBötzinger complex is not the only element involved in respiratory control, it is currently considered to be the main element responsible for its regulation. Alterations in this area can cause consequences of different magnitude, such as respiratory increase or depression. This can be caused by congenital lesions, trauma, Cardiovascular accidents or the administration of psychoactive substances. In extreme cases it can lead to the death of the patient.

It has been observed in postmortem analysis of people with dementia with Lewy bodies or atrophy usually observed a decrease in the population of neurons reactive to the above mentioned neurokinin-1, which may explain the presence of respiratory alterations in these diseases.

Bibliographic references:

• Beltran-Parrazal, L.; Meza-Andrade, R.; García-García, F.; Toledo, R.; Manzo- J.; Morgado-Valle, C. (2012). Central mechanisms of respiratory rhythm generation. Medical Journal. Brain mechanisms. Universidad Veracruzana, Mexico.

• García, L.; Rodríguez, O. and Rodríguez, O.B. (2011). Regulation of respiration: morphofunctional organization of its control system. University of Medical Sciences. Santiago de Cuba.

• Muñoz-Ortiz, J.; Muñoz-Ortiz, E.; López-Meraz, M.L.; Beltran-Parrazai, L. and Morgado-Valle, C. (2016). The pre-Bötzinger complex: generation and modulation of respiratory rhythm. Elsevier. Spanish Society of Neurology.

• Ramirez, J.M.; Doi, A.; Garcia, A.J.; Elsen, F.P.; Koch, H. & Wei, A.D. (2012). The Cellular Building Blocks of Breathing. Comprehensive Physiology; 2(4):2683-2731.