Many insecticides work by disrupting ACh synapses. Acetylcholine in manufactured directly in the presynaptic terminal. 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. Cell bodies found in the midbrain, pons and medulla, most near the midline of the brain stem. The behavioral effects are complex. LSD effects serotonergic receptors.