Inhibitory Neurotransmitters:

Inhibitory neurotransmitters are chemical messengers that block or prevent messages from being passed along any farther. Also see Excitatory Synapse, Excitatory Neurotransmitters, andInhibitory Synapse. For example:

• GABA (Gamma-AminoButyric Acid) helps control muscle activity and is an important part of the visual system. Drugs increasing the brain’s GABA levels can treat epileptic seizures and tremors in patients with Huntington’s disease.
• Serotonin constricts blood vessels, brings on sleep, and helps regulate temperature. Low levels of serotonin may cause sleep problems and depression. Too much can lead to seizures.