To explain this, I need to describe synaptic function. As you may know the nervous system consists of chains of nerve cells. When a nerve signal arrives at the junction or synapse between nerve cells, the first one releases vesicles containing chemicals called neurotransmitter which lock onto receptors on the next nerve cell. At the junction between an auditory nerve fibre, and the next nerve cell in the ' where is it' part of the auditory pathway, there is one of the largest and most efficient nerve endings in the brain. The size of these nerve endings and the multiple synapses which they make are an indication of how important it is to survival to know exactly where danger is coming from as a predator prepares to pounce on you.
Different neurotransmitters act to send or block nerve signals in different pathways in our brain.
Depending on which one is being used, different drugs can act on the pathway to stimulate or block it. So we need to know which neurotransmitter the auditory nerve uses so that we can deduce which drugs might be useful in enhancing or blocking auditory signals. In collaboration with Norwegian scientists from Oslo University, we have recently shown at Keele that the synapse made by the auditory nerve contains an amino acid called glutamate, and that this is released when the nerve is stimulated. This was shown by labelling the large nerve endings for glutamate and for its precursor glutamine, and seeing how the labelling decreased when the nerve terminals were depolarised. Well, glutamate is known to be a fast excitatory neurotransmitter in other parts of the nervous system.