Alzheimer’s disease (AD), which is the most common form of dementia, accounts for 60-70% of cases. The causes of Alzheimer’s have not yet been fully found.
But one of the hypotheses to explain the causes is the deficit of acetylcholine, among others, and a structure of the brain known as the Meynert’s basal nucleus and the temporal lobes are the regions of greatest deficit in this aspect.

This clear biochemical anomaly was studied and associated with the disease. And not only with Alzheimer’s disease, but also with Parkinson’s disease where the basal nucleus undergoes degeneration.

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

What is Meynert’s basal core?

The Meynert basal nucleus is defined as a group of nerve cells located in the innominate substance with broad projections to the neocortex, rich in acetylcholine and choline o-acetyltransferase. It is named after 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 Meynert basal nucleus plays an essential role through its axons directed to the whole bark, providing to the latter the highest contribution of acetylcholine.

The release of acetylcholine in the sensory areas triggers a succession of cellular events that lead to a series of synaptic modifications . The Papez circuit (structures that according to James Papez were related to the affective aspects of memory) and the Meynert basal nucleus seem to be involved in a process of retroaction aimed at consolidating memory and making it lasting.

The importance of acetylcholine

The importance of acetylcholine was discovered by Henry Hallet Dale and Otto Loewi, who shared the Nobel Prize in Physiology and Medicine in 1936. Otto Loewi began his research on the basis of Elliot’s hypothesis that the nerve impulse was transmitted through a chemical substance. Loewi was able to prove 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 and central nervous systems of mammals. It is involved in the regulation of various functions, such as cortical activation, switching from sleep to wakefulness, memory and association processes .

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

Your link to Alzheimer’s

People with mild cognitive impairment show evident atrophy of the Meynert basal nucleus, the brain structure from which originates 80% of cholinergic neurons that facilitate a wide range of cognitive functions such as memory. It has been observed that the lesions in this area of the brain are clearer in those patients whose memory loss was more significant. Using neuroimaging markers, early changes in the brain of people at high risk of Alzheimer’s can be determined.

One study estimated that in 2006, 0.4% of the population was affected by Alzheimer’s and that it would triple by 2050. Alzheimer’s disease is currently incurable and terminal. However, there are pharmacological and non-pharmacological treatments that show signs of efficacy, such as anticholinesterase drugs that have an inhibitory action on cholinesterase , the enzyme responsible for breaking down acetylcholine. The first to be marketed was tacrine, which has been discontinued due to its hepatotoxicity.

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