Neurotransmitters naturally occurring

Several naturally occurring amines mediate the transmission of nerve impulses and are referred to as neurotransmitters Two examples are epinephrine... 

Naturally Occurring Compounds. Many derivatives of iadole are found ia plants and animals where they are derived from the amino acid tryptophan. Several of these have important biological function or activity. Serotonin [50-67-9] (12) functions as a neurotransmitter and vasoconstrictor (35). Melatonin [73-31-4] (13) production is controlled daily by the circadian cycle and its physiological level iafluences, and seasonal rhythms ia humans and other species (36). Indole-3-acetic acid [87-51-4] (14) is a plant growth stimulant used ia several horticultural appHcations (37). 

Neurotransmitter (Section 22.4) Substance, usually a naturally occurring amine, that mediates the transmission of nerve impulses. 

Has no action when binding on its own to the receptor but only modulates the actions of the naturally occurring hormone or neurotransmitter when it is released. Therefore, the temporal aspects of the natural signaling mechanism are retained and desensitization is minimized. 

Many psychoactive drugs act to alter neurotransmitter functions either through effects on their synthesis, metabolism or reuptake or by directly affecting the receptors for naturally occurring compounds. For example, drugs such as prozac increase serotoniner-gic activity by selective serotonin reuptake inhibition (SSRI). 

GHB is a naturally occurring compound found in every cell of mammals. It occurs in greatest concentrations in tbe heart, kidney, and skeletal muscles. GHB is chemically related to gamma amino-butyric acid (GABA), a well-known neurotransmitter, and is thought by some researchers to itself act as a neurotransmitter in some parts of the GNS. 

Many naturally occurring compounds and an increasing number of synthesized chemicals work by influencing the effectiveness of a specific neurotransmitter. Typically, neurotransmitters are released from one neuronal cell and are picked up by specific receptors in the adjacent cell, which causes the receiving cell to react. The receptor then releases the neurotransmitter into the gap between the cells. At this time the neurotransmitter must be removed either by being broken down by a specific enzyme or it can be taken back up by the releasing cell to be reused. A compound can influence a neurotransmitter and thus the response of the receiving cell in several ways ... 

Glutamic Acid A non-essential amino acid naturally occurring in the L-form. Glutamic acid (glutamate) is the most common excitatory neurotransmitter in the central nervous system. 

Optical isomerism of drug molecules is widespread. Many drug molecules only contain one or two chiral centres. A simple example is the naturally occurring neurotransmitter adrenaline. When a compound has no symmetry about a particular carbon atom the carbon atom is said to be a chiral centre. When a compound contains one or more chiral centres it is able to rotate plane-polarised light to the right (+) or the left (-). A chiral centre arises when a carbon atom has four structurally different groups attached to it. 

Dopamine is a naturally occurring catecholamine it is the immediate biochemical precursor of the norepinephrine found in adrenergic neurons and the adrenal medulla. It is also a neurotransmitter in the CNS, where it is released from dopaminergic neurons to act on spe-cihc dopamine receptors (see Chapter 31). 

Baclofen (Lioresal) is the parachlorophenol analogue of the naturally occurring neurotransmitter y-aminobu-tyric acid (GABA). 

Atropine is an antagonist for the naturally occurring neurotransmitter (nerve signal carrier) acetylcholine. Its structural similarity to acetylcholine makes it very specific for acetylcholine receptors. How about its effects ... 

The first generation of antidepressants, MAO (monoamine oxidase) inhibitors, inhibited neurotransmitter degradation by inhibiting monoamine deoxidase, a flavin containing enzyme, found in the mitochondria of neurons and other cell types, that oxidatively deaminates naturally occurring sympathomimetic monoamines, such as norepinephrine, dopamine, and serotonin within the presynapse. In 1952, isoniazid and its isopropyl derivative, iproniazid (1), were developed for the treatment of tuberculosis, where it was subsequently found that these agents had a mood enhancing effect on... 

The discovery of a multitude of naturally occurring, bioactive peptides has generated a rich source of pharmacophores from which medicinal chemists are developing new useful therapeutic drugs. After binding to an enzyme, or a membrane receptor, peptide-based inhibitors, neurotransmitters, immunomodulators, and hormones influence cell-to-cell communications and control a variety of vital functions such as metabolism, immune defense, digestion, respiration, sensitivity to pain, reproduction, and behavior. 

Some naturally occurring neurotransmitters may be similar to drugs we use. For example, it is well known that the brain makes its own morphine (i.e., beta endorphin), and its own marijuana (i.e., anandamide). The brain may even make its own antidepressants, it own anxiolytics, and its own hallucinogens. Drugs often mimic the brain s natural neurotransmitters. Often, drugs are discovered prior to the natural neurotransmitter. Thus, we knew about morphine before the discovery of beta-endorphin marijuana before the discovery of cannabinoid receptors and anandamide the benzodiazepines diazepam (Valium) and alprazolam (Xanax) before the discovery of benzodiazepine receptors and the antidepressants amitriptyline (Elavil) and fluoxetine (Prozac) before the discovery of the serotonin transporter site. This un-... 

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