Those substances involved in production of exciters or inhibitory postsynaptic potentials, due to immediate effect of action on synaptic receptors, are known as neurotransmitters. Neuromodulators are another class of substances. These substances modify a specific response by acting in concert with the more direct acting neurotransmitters.

Neuromodulators and neurotransmitters those are most important in those parts of the CNS (central neural systems that are especially reactive to drugs are listed here.

1, Acetylcholine: especially active in the Hippocampus, Neocortex and

caudate nucleolus.

2, Biogenic monoamine.

3, Amino acids

Some peptides present in the neural system act as local hormones or act to neurotransmitters, thus giving a finer level of control. These are neuromodulators. As methods of identification become more sophisticated, the list of neurotransmitters and modulators substance is constantly being upgraded. Recent additions are: aspartic acid, which has an exciter action similar to that glutamate these drugs are used widely distributed in the central neural system areas associated with the control of pain.