receptor downregulation
Reduction in the number or sensitivity of cellular receptors in response to prolonged drug exposure.
Full Definition
Receptor downregulation is a cellular adaptation mechanism where continued exposure to a drug or neurotransmitter leads to decreased receptor density or reduced receptor sensitivity. This process involves internalization of receptors from the cell surface, decreased receptor synthesis, or increased receptor degradation. In psychopharmacology, receptor downregulation can contribute to tolerance development and may explain some delayed therapeutic effects. For example, antidepressants may initially block serotonin reuptake, but their therapeutic effects may depend on subsequent receptor adaptations including downregulation of presynaptic autoreceptors.
Usage
Usage note: Always hyphenate when used as a compound modifier; distinguish from upregulation in mechanism discussions.
In Context
- "The delayed onset of antidepressant effects may reflect time needed for receptor downregulation and synaptic adaptations." — Clinical pharmacology review
- "Chronic benzodiazepine use can lead to GABA receptor downregulation, contributing to tolerance and withdrawal symptoms." — Addiction medicine article