A Brief Overview of Neurotransmitter Distribution and Function
(abstracted from Physiology of Behavior 7th Ed, 2001, by Neil Carlson)


Category Where found. Actions Odds & Ends
Acetylcholine Motor neurons from CNS Control of all voluntary muscle movement Many insecticides work by disrupting ACh synapses.  Humans have a blood enzyme that destroys the insecticides; insects don't.

Acetylcholine in manufactured directly in the presynaptic terminal.  In view of some of its functions, can you think of an advantage to this?

Target organs of the parasympathetic system Parasympathetic responses
Widely distributed in the brain:  
     --dorsolateral pons REM sleep involvement
     --basal forebrain cortical activation & perceptual learning
     --medial septum regulation of hippocampus & memory formation
Category Where found. Actions Odds & Ends
Monoamines Neuron cell bodies located in the brainstem, w/ multi-branching axons that terminate throughout many brain regions.  neuromodulation  
     --dopamine Axons terminate in many places, including the basal ganglia (movement) and limbic system (emotions & memory) Implicated in: movement, attention, learning and the reinforcing effects of abused drugs. Degeneration of dopaminergic neurons in the substantia nigra produces Parkinson's disease. 
Cell bodies are primarily in the pons and medulla.  Axons terminate widely throughout the brain. In general, the behavioral effects are excitatory.  Important in vigilance and attention.  
     --serotonin Cell bodies found in the midbrain, pons and medulla, most near the midline of the brain stem. The behavioral effects are complex. Involved in mood regulation, eating, sleep, arousal, pain and the control of REM. Prozac acts on serotonin receptors.

LSD effects serotonergic receptors.

Category Where found. Actions Odds & Ends
Amino Acids These are the most common neurotransmitters in the CNS. neuromodulation  
     --glutamate  Prevalent  in very primitive organisms--early evolutionary development.   Glutamate is the primary excitatory neurotransmitter in the CNS.  
     --GABA Prevalent  in very primitive organisms--early evolutionary development.   GABA is the primary inhibitory neurotransmitter in the CNS; abnormalities may be involved in seizure disorders.   GABA agonists include: Valium and Librium (anti-anxiety) and barbiturates (sedatives & seizure disorder treatment)
    --glycine spinal cord General inhibitory effects.   Strychnine, which causes death via convulsions, is a glycine antagonist.
Category Where found. Actions Odds & Ends
Peptides Many different peptides are formed in the cell bodies of neurons located throughout the CNS. Endogenous opioids (endorphins) are involved in analgesia, species-specific defense reactions and reinforcement.   Heroin and percodan are opiod agonists.  Naloxone is an antagonist used to treat opiate intoxication. Endorphins were discovered by accident.  In 1973, Solomon Snyder & Candace Pert at Johns Hopkins identified receptor sites for heroin molecules.  Since it seemed unlikely that there would be brain sites specific to chemicals found in the sap of flowers which grow in Asia, this pointed toward naturally occurring neurotransmitters chemically similar to the opiates. [thanks Chris] 
Category Where found. Actions Odds & Ends
Soluble gases NO is widely used by neurons throughout the body.  CO is less well understood. Involved in control of muscles in intestinal walls, dilates blood vessels in active brain areas and dilates blood vessels that produce penile erections. An off-the-wall question for you:  Is there any chance that NO or CO as neurotransmitters might be involved in asphyxiophilia?