Pharmacology for Anaesthesia and Intensive Care

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3 Drug action

TP

NH 2

α

GDP

COOH

γ

β

agonist

(b)

(a)

α

Adenylyl

cyclase

GDP

COOH

γ

β

NH 2

Extracellular

Intracellular

Adenylyl

cyclase

Figure 3.2.Effect of ligand-binding to G-protein Coupled Receptor (GPCR). Ligand binding to

the 7-TMD GPCR favours association with the G-Protein, which allows GTP to replace GDP. Theα

unit then dissociates from the G-protein complex to mediate enzyme and ion-channel

activation/inhibition.