The Development of the False Neurotransmitter Concept of Hepatic Encephalopathy
The concept of weak, or false, neurochemical transmitters arose in the early 60’s to describe a series of potential neurotransmitters which were similar in structure to true aminergic neurotransmitters, norepinephrine and epinephrine, and which, when tested pharmacologically, manifested weak, or in some cases, almost absent Pharmacological action.l According to this concept, the sympathetic nerve or, by extension, the central nervous system, is unable to select between amines presented to it, that is unable to detect or choose between various aminergic neurotransmitters, provided they meet minimum structural requirements. In the case of the catecholamine and aminergic nerves, these structural requirements include a phenolic ring and a beta hydroxy group on a short carboxyl side change. It is curious that the normal adrenergic nervous system is incapable of distinguishing between these various potential neurotransmitters and that the maintenance of normal neurotransmitter profiles within the peripheral sympathetic nerve or the central nervous system is apparently dependent on the regulating ability of the liver to regulate different metabolites, including the precursors of these various adrenergic transmitters, namely the aromatic and heterocyclic amino acids.
KeywordsHepatic Encephalopathy Aromatic Amino Acid Neutral Amino Acid Plasma Amino Acid Hepatic Coma
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