Traditional Approaches-Psychopharmacology:  Background Material

Effective Treatments Index

Neurotransmitters have two general effects:

1) to hyperpolarize or excite or stimulate, and 

2) to depolarize or inhibit or block.To date, more than fifty substances are either known or strongly suspected as neurotransmitters within the brain.The list grows longer each year as more becomes known about the physiology and the chemical processes within the human body. The table below attempts to summarize what is currently known about each.

Substance Site of Action Action Effect
Primary neurotransmitter of the CNS.  May excite or inhibit
Elicit REM sleep  
Acetylcholine Basal forebrain Activate cerebral cortex Facilitate learning especially perceptual learning
Acetylcholine Located in the medial septum Acts on hippocampus  Control electrical rhythms and modulate its functions including those involved with memory formation

May excite or inhibit, Generally excitatory in terms of behavior

Majority of norepinephrine neurons are located in the pons, medulla, and thalamus Acts on almost every region of the brain, released through axonal variscosities versus terminal buttons Involved in sexual behavior and in control of appetite

Generally inhibitory

Brain and spinal cord primarily in the midbrain, pons, and medulla

Interesting fact: At least nine different types of serotonin receptors have been identified to date 

Released from variscosities versus teminal buttons affecting the cerebral cortex, basal ganglia, and hippocampus Implicated in mood regulation, control of eating, sleep and dreaming, arousal, and in pain regulation

Generally excitatory, depends on the postsynaptic receptor

Brain contains multiple dopaminergic neuron systems, most important is located within the midbrain in the substantianigra and the ventral tegmental area Acts primarily on the limbic system, the basal ganglia, and the frontal cortex Implicated in a variety of functions including movement, attention, learning, planning and strategizing,formation of memory, and reinforcing the effects of drugs of abuse
Gamma aminobutyric acid (GABA)

Postsynaptic inhibition

Brain and spinal cord Believed to be interconnected with the functions of glutamate to maintain the body’s balance Investigators surmise that one of the causes of epilepsy is an imbalance of GABA secreting neurons or in the number of GABA receptors

Postsynaptic inhibition

Spinal cord and lower portions of the brain Controls a chloride channel and produces an inhibitory effect.Some terminal buttons release both glycine and GABA which is believed to produce rapid onset, long lasting postsynaptic potentials  
Lipids Chemical substances derived from these may be involved in the transmission of messages within or between individual cells May affect calcium and potassium channels  

Generally inhibitory

Neurons of the CNS Synthesis of these peptides occurs within the cell body of the neuron, released from all parts of the terminal button and not just the active zone resulting in only a portion being present in the synaptic cleft Most appear to work as neuromodulators although some work as neurotransmitters, of particular interest are the endorphins and enkephalins and their receptor sites


Present in all cells Functions as a neuromodulator
Suppresses neural activity and generally has an inhibitory effect on behavior

Caffeine produces excitatory effects through blocking adenosine receptors. 

Nitric Oxide

(Soluble gas)

Produced by the activity of an enzyme found in certain neurons, can be produced in several parts of the neuron including the dendrites and is released immediately – used as a messenger in numerous parts of the body Acts on blood vessels and the muscular wall of the intestines Involved in control of the muscular wall of the intestines, stimulates changes in blood vessels that result in penile erection,dilates blood vessels in regions of the brain that are metabolically active Nitric oxide is produced by metabolic processes in the brain with may contribute to brain degeneration