Neurological Control

Presynaptic Control of Neurotransmitter Release

The release of a neurotransmitter from its nerve terminal is not only dependent upon the passage of an action potential , but also on the intersynaptic concentration of the transmitter. This is known as presynaptic inhibition. At certain synapses, such as noradrenergic, GABAergic, dopaminergic and serotonergic synapses, the release of the neurotransmitter may be reduced by the presence of high concentrations of the transmitter in the synaptic cleft . The release of a neurotransmitter can also be affected by a variety of other neurotransmitters , for example, stimulation of serotonin receptors on noradrenergic terminals can lead to an enhanced release of noradrenaline. Such receptors are termed heteroceptors.
Neurons  and synapses occur in specific patterns in the brain, giving rise to complex neuronal circuits. This results in the specialisation of different regions of the brain for different functions and allows us to integrate information such as sound, vision, smell, taste and touch. Each neurotransmitter is made by a small number of neurons whose cell bodies are clustered in specific areas of the brain. For example, noradrenaline is synthesised mainly by neurons in the brainstem  , specifically in the locus coeruleus , which is situated in the pons  ; the cell bodies of the dopamine neurons are clustered in a few brain regions, most importantly those deep within the
midbrain  , in the substantia nigra  . However, the axons  of these neurons extend throughout the brain and influence almost the entire organ.

Find out more about noradrenaline