Neurotransmitter

Neurotransmitters are chemicals that are used to relay, amplify and modulate electrical signals between a neuron and another cell. According to the dogma of the 1960's, a chemical can be classified as a neurotransmitter if it respects the following conditions:

Post-synaptic effect

A neurotransmitter's effect is determined by its receptor. For example, GABA can act on both rapid or slow inhibitory receptors (the GABA-A and GABA-B receptor respectively). However many other neurotransmitters can have excitatory or inhibitory actions depending on which receptor they bind to.

Related Topics:
GABA - GABA-A - GABA-B

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Neurotransmitters may cause either excitatory or inhibitory post-synaptic potentials. That is, they may help the initiation of a nerve impulse in the receiving neuron, or they may discourage such an impulse, by modifying the local membrane voltage potential. In the central nervous system, combined input from several synapses is usually required to trigger an action potential. Glutamate is the most prominent of excitatory transmitters; GABA and glycine are well-known inhibitory neurotransmitters.

Related Topics:
Glutamate - GABA - Glycine

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Many neurotransmitters are removed from the synaptic cleft by a process is called reuptake (or often simply uptake). Without reuptake, the molecules might continue to stimulate or inhibit the firing of the postsynaptic neuron. Another mechanism for removal of a neurotransmitter is digestion by an enzyme. For example, at cholinergic synapses (where acetylcholine is the neurotransmitter) the enzyme acetylcholinesterase breaks down the acetylcholine. Neuroactive peptides are usually removed from the cleft by diffusion, and eventual break down by proteases.

Related Topics:
Reuptake - Enzyme - Acetylcholine

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