Acetylcholine deficiency

New experimental results suggest berberine may have a potential for inhibition and prevention of AD due to the multiple activities that berberine possesses including antioxidant activity, AChE and BChE inhibitory activity, MAO inhibitory activity, and its abilities to reduce Ap peptide level and to lower cholesterol. Many studies have proved AChE-inhibiting property of berberine [83-85]. AChE is mainly present in the central nervous system and its major role is to catalyze the hydrolysis of the neurotransmitter acetylcholine to choline. This process can return an activated cholinergic neuron to its resting state. The pathogenesis of AD is linked to acetylcholine deficiency in the brain. 

Choline was isolated from ox bile in 1849 by Strecker. During 1900 to 1920, observations led to interest in the vasodepressor properties of the esters of choline, and in the 1920s it was shown that acetylcholine was presumably the "vagus-substance." The nutritional importance of choline was recognized in the 1930s, when it was found that choline would prevent fatty infiltration of the Hver in rats. Subsequent observations showed that choline deficiency could produce cirrhosis (1) or hemorrhagic kidneys (2) in experimental animals under various conditions. 

Acetylcholine receptor deficiency. The degree of disease severity may vary from mild to very severe. In general, patients harboring low-expressor or even homozygous null mutations in the AChR subunit may experience... 

Deficiency of acetylcholine causes an imbalance in cholinergic-adrenergic activity and can increase the risk of manic episodes. 

Traditionally, most affective disorders have been treated with compounds that resemble the neurotransmitters that are deficient or in excess in specific brain regions. The aberrant levels of neurotransmitters (or their receptors), such as norepinephrine, dopamine, acetylcholine, and serotonin, have correlated with behavioral symptoms of schizophrenia, depression, anxiety, sleep disorders, motor dysfunctions, attention difficulties, and cognitive disorders. Most drugs discovered for these disorders resulted from screening compounds directly in rodent behavioral models that mimic the behavior of the disease. In these cases, the molecular target" or mechanism of action was assumed to be the deficiency or excess of a neurotransmitter. 

The only known change in neurotransmitter metabolism so far detected is a deficiency of acetylcholine in the brain. This has been shown in post-mortem studies on the brains of patients with Alzheimer s disease. Some success in reducing the symptoms of the disease has been obtained with drugs that inhibit the activity of acetylcholinesterase leading to an increase in the acetylcholine concentration, but the improvement is minimal so that its use is controversial. 

Pantothenic acid (vitamin B5) is both present in many nutrientcients and it is also produced by intestinal bacteria. Deficiency is therefore thought to be unlikely. Its active form, 4-phosphopantetheine, is an element of both coenzyme-A and acyl-carrier protein and thus participates in fatty acid synthesis and in the posttranslational modification of proteins. Acetylcoenzyme-A is important for the synthesis of the neurotransmitter acetylcholine. 

Medicinal chemistry has many examples of the development of successful therapeutics based on an exploration of endogenous compounds. The treatment of diabetes mellitus, for example, is based upon the administration of insulin, the hormone that is functionally deficient in this disease. The current treatment of Parkinson s disease is based upon the observation that the symptoms of Parkinson s disease arise from a deficiency of dopamine, an endogenous molecule within the human brain. Since dopamine cannot be given as a drug since it fails to cross the blood-brain barrier and enter the brain, its biosynthetic precursor, L-DOPA, has been successfully developed as an anti-Parkinson s drug. Analogously, the symptoms of Alzheimer s disease arise from a relative deficiency of acetylcholine within the brain. Current therapies for Alzheimer s-type dementia are based upon the administration of cholinesterase... 

The medicinal chemistry of Alzheimers is complicated by the fact that the etiology of this disease is still far from clear. Evidence points to an association with decreased levels of acetyl choline in the brain. Many of the drugs that have been introduced to date for treating this disease thus comprise agents intended to raise the deficient levels of that neurotransmitter by inhibiting the loss of existing acetylcholine due to the action of cholinesterase. A compound based on an indene that, perhaps surprisingly, inhibits that enzyme has been proposed for the treatment of Alzheimer s. Aldol condensation of piperidine aldehyde (4-2) with the indanone (4-1) from cyclization of 3,4-dimethoxycinnamic acid leads to the olefin (4-3). Catalytic reduction removes the double bond to afford donepezil (4-4) [3]. 

The devastating mental deterioration that characterizes Alzheimer s disease has been attributed to a mishandling of the neurotransmitter acetylchohne. Inhibitors of acetylcholinesterase, the enzyme that catabolizes that substance, would be expected to help restore deficient acetylcholine levels. Several partly reduced acridines have shown some activity in treating Alzheimer s disease. At least one of these, tacrine (14-5), is now approved for use in patients. The initial step in the synthesis of the first of these consists of the sodium amide catalyzed condensation of isatin (14-1) with cyclohexanone. The reaction can be visualized by assuming the first step to involve an attack of amide on isatin to give an amido-amide such as (14-2) (note that no attempt has been made to account for charges). This can then react with... 

In fact, the SSRI-RBD link sounds a lot like the Thorazine-tardive dyskinesia tie-in, doesn t it What possibly common underlying mechanism could unite these apparently disparate phenomena One answer is dopamine, whose production by the substantia nigra is deficient in spontaneous Parkinsonism. Dopamine is blocked, hence rendered functionally deficient, by the antipsychotics that produce both immediate and delayed Parkinsonian side effects. Serotonin inhibits dopamine, which means that potentiating serotonin with SSRIs could also render dopamine less functionally efficacious. Acetylcholine is in dynamic reciprocity with both serotonin and dopamine. Acetycholine causes an increase in dopamine s efficacy in some circuits and a decrease in others. 

FIGURE 11—10. This figure shows what happens to acetylcholine activity when dopamine receptors are blocked. As dopamine normally suppresses acetylcholine activity, removal of dopamine inhibition causes an increase in acetylcholine activity. Thus, if dopamine receptors are blocked, acetylcholine becomes overly active. This is associated with the production of extrapyramidal symptoms (EPS). The pharmacological mechanism of EPS therefore seems to be a relative dopamine deficiency and an acetylcholine excess. 

Anticholinergics (see Table 10-2) Inhibit excessive acetylcholine influence caused by dopamine deficiency. Use in Parkinson disease limited by frequent side effects. 

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