Central Nervous System Neurotransmitters, Receptors, and Drug Targets
substances within the CNS modulate neurotransmitter actions.
ACh and norepinephrine (NE), predominant in the PNS, also function in the CNS.
Dopamine and 5HT (serotonin)—more prominent in the CNS—and peptides such as
endorphins are important in CNS function. Transduction mechanisms for
neurotransmitter action are similar to those in the PNS: ionotropic types
include voltagegated ion channels (respond to membrane potential changes) and
ligandgated ion channels (alter membrane ion
permeability in response to ligands such as neurotransmitters or drugs).
Metabotropic types include GPCRs and involve secondmessenger pathways (affect
ion channels or biochemical reactions). Drugs affect various sites along neuronal
pathways, including neurotransmitter synthesis, storage, and release; receptor
activation and inhibition; modulation of intrasynaptic neurotransmitter
metabolism or reuptake; and direct secondmessenger