Neurotransmitter

Definition

A chemical signaling molecule released from the presynaptic terminal of a neuron into the synaptic cleft, where it binds to receptors on a postsynaptic cell—typically another neuron, muscle fiber, or gland cell—to propagate or modulate an electrical signal. In arthropods, neurotransmitters mediate rapid neuromuscular control, sensory processing, and central pattern generation for behaviors such as flight, web-building, and escape responses.

Etymology

From Greek neuron (nerve, sinew) + Latin transmittere (to send across)

Example

The insecticide fipronil blocks GABA-gated chloride channels, prolonging inhibitory neurotransmitter signaling and causing lethal convulsions in target insects; in spiders, glutamate serves as the primary excitatory neurotransmitter at neuromuscular junctions.

Related Terms

• Synapse
• neuromuscular junction
• Acetylcholine
• GABA
• glutamate
• biogenic amine
• neuropeptide
• receptor
• Axon
• synaptic vesicle

Usage Notes

Distinguish from neuromodulators (diffuse, slower-acting) and neurohormones (released into circulation). Arthropod neurotransmitter systems differ markedly from vertebrates: insects use glutamate rather than acetylcholine at most excitatory neuromuscular synapses, and many pesticides exploit these phylogenetic differences. The term is sometimes used loosely for any synaptic messenger, but purists reserve it for small-molecule fast transmitters (acetylcholine, amino acids, biogenic amines), excluding neuropeptides.