Source Cells | Release | Reuptake | Removal Mechanism | Synaptic Transmission | Receptors | |
---|---|---|---|---|---|---|
Neurotransmitters | Neuron | Exocytotic vesicle | Yes | Enzyme-dependent | Pre- to postsynaptic membrane | Membrane receptors a necessity |
Gasotransmitters | All cell types, including neurons | Released as produced, (usually) not stored | No | Nonenzymatic: diffusion, oxidation, scavenging, methylation, etc. | Forward and retrograde diffusion | No classic membrane receptors needed |