A recent American study looked at the hypothalamus. This region of the brain is none other than the control center for several functions such as hunger, stress or wakefulness. According to the researchers, an excess of salt would reduce blood flow there, a rather surprising phenomenon.
When neurons are active in our brain, they need oxygen and glucose . They are then transported through the blood for a supply in phase with the demand of the neurons. Thus, several biological mechanisms are at work to increase blood flow. Science has already observed this phenomenon in the cerebral cortex, a region of the brain also called "gray matter". Researchers at Georgia State University (United States) have focused their interest on the same phenomenon, this time at the level of the hypothalamus. Their work was published in the journal Cell Reports on November 2, 2021. However, their observations are very surprising.
Recall in passing that the hypothalamus is a structure of the central nervous system located on the ventral side of the brain. The size of a simple almond, the hypothalamus is involved in the regulation of the autonomic nervous system and endocrine functions. It also plays a role in many behavioral bodily functions such as thermoregulation, stress, hunger, circadian rhythm or even reproduction.
The supraoptic nucleus of the hypothalamus contains neurons whose main activity is the secretion of vasopressin. This is a hormone that plays an important role in regulating blood salt concentration . However, if the neurons see their activity favored by the increase in blood flow, an excess of salt should logically be linked to the increase in blood flow to feed the neurons which are activated precisely to correct this excess.
Yet researchers have observed the opposite phenomenon. Within the supraoptic nucleus of the hypothalamus, excess salt in the bloodcauses vasodilation, i.e. an increase in the diameter of blood vessels by dilation of their muscle fibres. However, the blood flow decreases significantly, which generates hypoxia (oxygen deprivation) that affects the cells in a localized way.
Javier Stern, neuroscientist and lead author of the study, says that eating very salty causes sodium levels in the body to stay high for a long time. One of the hypotheses is that hypoxia makes it possible to reinforce the capacity of neurons to respond to continuous saline stimulation and to remain active for a significant period of time. For scientists, this work could provide details on the phenomenon of hypertension, which is often caused by a diet that is too high in salt.
