Abstract
Of relevance to the field of psychopharmacology, the largest group of receptors are proteins. These include receptors for endogenous hormones, growth factors, and neurotransmitters; metabolic enzymes or signaling pathways; transporters and pumps; and structural proteins. Usually the drug effect is measured at a much more complex level than a cellular response, such as the organism level. Receptor occupancy theory assumes that drug action is dependent on concentration and the attendant quantitative relationships are plotted as dose- or concentration- response curves. Drugs often act at receptors for endogenous hormones and neurotransmitters, and these receptors have evolved to recognize their cognate signaling molecules. Most neuron-to-neuron communication in the central nervous system involves chemical neurotransmission at up to a quadrillion of synapses. The chapter illustrates the comparison of presynaptic terminals for the biogenic amine neurons: dopamine, norepinephrine, and 5-hydroxytryptamine. The role of biogenic amines in affective disorders has a long history, beginning in the 1950s.