Receptoroperated

Receptor-operated refers to cellular processes in which activation of a cell-surface receptor directly modulates ion channel activity or intracellular signaling without a primary reliance on membrane depolarization. The term is used to describe both ligand-gated ion channels that open a pore upon receptor binding and receptor-initiated signaling pathways where a receptor activates second messengers that influence channels or execute cellular responses.

Directly gated ligand-activated channels include nicotinic acetylcholine receptors, GABA_A and glycine receptors, and the serotonin 5-HT3 receptor, which open their ion-conducting pore when a specific neurotransmitter binds. P2X purinergic receptors are another class of receptor-operated ion channels activated by extracellular ATP. In addition, many receptors that are not ion channels, such as G protein-coupled receptors (GPCRs), trigger receptor-operated signaling cascades. Activation of GPCRs can stimulate phospholipase C to generate IP3 and DAG, leading to calcium release from stores and subsequent activation of calcium-sensitive channels, or to the opening of certain channels directly via G protein subunits.

Receptor-operated processes are distinct from voltage-operated channels, which require depolarization to open. In practice, the same ion channel can be influenced by both receptor-operated and voltage-dependent mechanisms in different cellular contexts. The term is sometimes used variably in the literature, and "ligand-gated" is often used to describe receptor-operated channels with direct ligand-gating, while "GPCR-activated" or "second-messenger" pathways describe the signaling side.