A neuroscience dictionary and reference manual for the curious.

A neurotransmitter is a chemical messenger used by neurons and other excitable cells. In the classical model, it is made by a neuron, released from the presynaptic terminal, crosses the synaptic cleft, and binds to receptors on a postsynaptic cell. This binding can excite the receiving cell, inhibit it, or modulate how it responds to other signals.