Amines 381 Chemical messengers

The gap across the synapse is so small that the chemical messenger (neurotransmitter) crosses the cleft in less than a millisecond. Within the brain there are more than 50 neurotransmitters, which include amino acids, amines, purines, peptides and some gases. In contrast, in the peripheral nervous system there are only two, acetylcholine and noradrenaline. One of several questions concerning the concept of neurotransmitters is whether they differ, in principle, from local hormones (See below and Chapter 12). 

Neurotransmitters are not only chemical messengers for the nervous system, they may also be partly responsible for our moods. A simplified biochemical theory of mental illness is based on two amines found in the brain. The first is norepinephrine (NE). When an excess of norepinephrine is formed in the brain, the result is a feeUng of elation. Extreme excesses of NE can even induce a maific state, while low NE levels may be a cause of depression. 

Neurotransmitters are the chemical messengers of the nervous system. They carry nerve impulses from one nerve cell (neuron) to another. The most important neurotransmitters are acetylcholine and three other amines norepinephrine, dopamine, and serotonin. 

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