A natural neuroactive substance (NAS) is a chemical synthesized by neurons that affects the actions of other neurons or muscle cells. Natural neuroactive substances include neurotransmitters, neurohormones, and neuromodulators.[1] Neurotransmitters work only between adjacent neurons through synapses. Neurohormones are released into the blood and work at a distance. Some natural neuroactive substances act as both transmitters and as hormones.
2.1 Natural Neuroactive Substance (NAS): A chemical agent synthesized by a neuron which affects the properties of other neurons and/or muscle cells. 2.2 Neurotransmitter (NT). 2.3 Neuromodulator (NM). 2.4 Neurohormone (NH)