21 -G Protein-Coupled Receptors (GPCRs) and Adrenergic Signalling - Vocabulary Flashcards

Vocabulary flashcards covering GPCR signaling, adrenoceptor subtypes, their G protein coupling, second messengers, key agonists/antagonists, and clinical uses.

GPCR (G Protein-Coupled Receptor)

A family of cell-surface receptors with seven transmembrane helices that activate intracellular G proteins to relay signals inside the cell.

Adrenoceptors

Receptors for catecholamines, divided into alpha (a) and beta (b) subtypes that mediate sympathetic responses.

a1 Adrenoceptor

A Gq-coupled receptor that activates phospholipase C, increasing IP3 and DAG, leading to Ca2+ mobilization and smooth muscle contraction.

a2 Adrenoceptor

A Gi-coupled receptor that inhibits adenylyl cyclase, reducing cAMP and transmitter release.

b1 Adrenoceptor

A Gs-coupled receptor that stimulates adenylyl cyclase, increasing cAMP and enhancing heart rate and contractility.

b2 Adrenoceptor

A Gs-coupled receptor that stimulates adenylyl cyclase, increasing cAMP; causes bronchodilation and vascular/uterine relaxation.

b3 Adrenoceptor

A Gs-coupled receptor that increases cAMP, promoting lipolysis and thermogenesis in adipose tissue.

G proteins (Gs, Gi, Gq)

Intracellular proteins that transduce signals from GPCRs to effectors: Gs stimulates AC, Gi inhibits AC, Gq activates PLC.

Adenylyl cyclase

Membrane enzyme converting ATP to cAMP; stimulated by Gs and inhibited by Gi.

cAMP

Second messenger that activates PKA and modulates various cellular processes.

PKA (Protein Kinase A)

Kinase activated by cAMP; phosphorylates multiple intracellular targets.

PLC (Phospholipase C)

Enzyme activated by Gq that cleaves PIP2 into IP3 and DAG.

IP3 (Inositol trisphosphate)

Second messenger that releases Ca2+ from the endoplasmic reticulum.

DAG (Diacylglycerol)

Second messenger that activates protein kinase C (PKC).

Ca2+ (Calcium)

Key intracellular second messenger involved in muscle contraction and secretion; mobilized by IP3.

Noradrenaline (Norepinephrine)

Primary sympathetic postganglionic transmitter; acts on adrenergic receptors.

Adrenaline (Epinephrine)

Hormone from the adrenal medulla; acts on both alpha and beta adrenergic receptors.

Phenylephrine

Selective alpha-1 adrenergic receptor agonist.

Clonidine

Selective alpha-2 adrenergic receptor agonist.

Dobutamine

Selective beta-1 adrenergic receptor agonist; primarily increases cardiac output.

Salbutamol (Albuterol)

Selective beta-2 adrenergic receptor agonist; bronchodilator.

Terbutaline

Selective beta-2 adrenergic receptor agonist.

Salmeterol

Long-acting selective beta-2 adrenergic receptor agonist.

Mirabegron

Prodrug for a selective beta-3 adrenergic receptor agonist; used for overactive bladder.

Yohimbine

Alpha-2 adrenergic receptor antagonist.

Idazoxan

Alpha-2 adrenergic receptor antagonist.

Prazosin

Alpha-1 adrenergic receptor antagonist.

Doxazosin

Alpha-1 adrenergic receptor antagonist.

Atenolol

Beta-1 adrenergic receptor antagonist.

Metoprolol

Beta-1 adrenergic receptor antagonist.

Butoxamine

Beta-2 adrenergic receptor antagonist.

Propranolol

Non-selective beta-adrenergic receptor antagonist.

Phenoxybenzamine

Non-selective alpha-adrenergic antagonist used before pheochromocytoma surgery.

Adrenergic agonists (uses)

Drugs that activate adrenergic receptors; used for conditions like cardiac arrest, anaphylaxis, asthma, and local anaesthetic duration.

Adrenergic antagonists (uses)

Drugs that block adrenergic receptors; used to treat hypertension, BPH, pheochromocytoma, and other conditions.