General introduction and definitions

Abstract

The term“neurotransmitter” was coined by Elliot as long ago as 1904 to describe chemical compounds which are stored in the nerve cells of the brain, and indeed of other organs, and which are released from their stores by physiological or pathological stimuli. After release the neurotransmitter molecules cross the synaptic cleft, i.e. the gap between the nerve fibres, to act upon the receptors, where they produce their specifiic effects. This transmission of nervous activity may involve voluntary movement of some kind, involuntary actions such as breathing, digestion etc., an emotion or a change of mood, intellectual or creative thought processes or the experiencing of some kind of sensory input.