Intracellular signalling is the chain of events inside a cell after a receptor is activated. Dopamine receptors influence enzymes, second messengers, ion channels and proteins that regulate cellular activity. D1-like receptors generally increase cyclic AMP signalling, while D2-like receptors generally reduce it through different G proteins.
Dopamine acts through five recognised receptor subtypes: D1, D2, D3, D4 and D5. They are proteins that convert chemical binding into changes inside a cell. D1-like and D2-like families use different signalling pathways, but their overall effects depend on the cells and networks in which they operate.
These broad patterns do not mean one receptor family always excites behaviour and the other always inhibits it. A change in an inhibitory neuron can have a different network effect from the same change elsewhere. Receptors also engage multiple pathways, and chronic exposure can produce adaptations. This complexity helps explain why binding alone cannot predict the full experience of a medicine. Molecular models are valuable for drug development, but direct clinical evidence is needed to establish whether a proposed signalling difference improves symptoms or tolerability in people.
Second messengers translate a receptor event into changes within a cell. Their effects can alter firing, transmitter release or longer-term cellular responses. Network consequences then depend on which cells are involved. This sequence explains why a molecular action may be well established while its contribution to a complex outcome, such as motivation or cognition, remains uncertain and requires clinical investigation.
Further reading: Research record 10739409; Research record 17277774; Research record 8584611; Research record 8935801.
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