Basal nucleus of Meynert: what is it and what are its functions?

This part of the brain, a cluster of neurons, is closely related to Alzheimer's disease.

Alzheimer's disease (AD), the most common form of dementia, accounts for 60% to 70% of cases. The causes of Alzheimer's disease have not yet been fully understood. But one of the hypotheses to explain the causes is a deficit of acetylcholine, among other things, and a brain structure known as the nucleus of the brain. a brain structure known as the nucleus basalis of Meynert and the temporal lobes are the regions of greatest deficit in this respect.

This clear biochemical abnormality has been studied and associated with the disease. And not only with Alzheimer's disease, but also with Parkinson's disease where the basal nucleus suffers degeneration.

In this article we will see what the Meynert nucleus basalis is and what we know about this part of the nervous system and its involvement in the disease.

What is the nucleus basalis of Meynert?

The nucleus basalis of Meynert is defined as a group of nerve cells located in the substantia innominata, with extensive projections to the neocortex with extensive projections to the neocortex, rich in acetylcholine and choline o-acetyltransferase. It is named after the psychiatrist, neuropathologist and anatomist Theodor Meynert, who believed that alterations in brain development could be a predisposition to psychiatric diseases. He also argued that certain psychoses are reversible.

The nucleus basalis of Meynert plays an essential role through its axons directed to the whole cortex, it provides the latter with the major supply of acetylcholine.

The release of acetylcholine in the sensory areas triggers a succession of cellular events that lead to a series of modifications without a series of synaptic modifications that lead to. The Papez circuit (structures that according to James Papez were related to the affective aspects of memory) and the basal nucleus of Meynert seem to be involved in a feedback process aimed at consolidating the memory and making it lasting.

The importance of acetylcholine

The importance of acetylcholine was discovered thanks to Henry Hallet Dale and Otto Loewi, who shared the Nobel Prize in physiology and medicine in 1936. Otto Loewi began his research based on Elliot's hypothesis that the nerve impulse was transmitted through a chemical substance. Loewi was able to demonstrate that in the parasympathetic nervous system this substance was mainly acetylcholine, a substance that Henry Hallet Dale had previously isolated.

Acetylcholine was the first neurotransmitter characterized in both the peripheral nervous system and the central nervous system of mammals. It is involved in the regulation of several functions, such as cortical activation cortical activation, sleep-wake transition, memory and association processes..

Acetylcholine is synthesized in neurons by the enzyme cholinacetyltransferase from choline and acetyl-CoA in the synaptic cleft.

Its link to Alzheimer's disease

People with mild cognitive impairment show obvious atrophy of the nucleus basalis of Meynert, the brain structure from which 80% of the choline-acetyltransferase neurons in the brain are derived. 80% of the cholinergic neurons that facilitate a Wide range of functions. that facilitate a wide range of cognitive functions such as memory. It has been observed that lesions in this area of the brain are clearer in those patients whose memory losses were more significant. Neuroimaging markers can determine early changes in the brains of people at high risk for Alzheimer's disease.

One study estimated that in 2006, 0.4% of the population was affected by Alzheimer's disease and that it would triple by the year 2050. Alzheimer's disease is currently incurable and terminal. However, there are pharmacological and non-pharmacological treatments that show signs of efficacy, for example anticholinesterase drugs that have an inhibitory action on cholinesterase, the enzyme responsible for the breakdown of cholinesterase.the enzyme responsible for breaking down acetylcholine. The first to be marketed was tacrine, which is no longer used because of its hepatotoxicity.

The anticholinesterase drugs available are donepezil (Aricept), rivastigmine (Exelon or Prometax) and galantamine (Reminyl). None of these four drugs is indicated to slow or stop the progression of the disease. However, these drugs have been reported to have some efficacy in mild and moderate stages of the condition, but no effect in advanced stages.