Overview G protein-coupled receptors (GPCR) login to view 3 more bullets 3 types of GPCR second messengers and functions login to view 10 more bullets Receptor Types Adrenoceptor: Sympathetic System Receptor GPCR Class Locations and Major Functions α1 q GI and GU: contraction of sphincters Eye: contraction of iris radial muscle (mydriasis) Vasculature: vasoconstriction α2 i GI: ↓ motility Vasculature: vasoconstriction of veins and arteries in heart BUT vasodilation of arteries Presynaptic adrenergic nerve terminals: ↓ sympathetic outflow by inhibiting NE release Lipocytes: ↓ decreases lipolysisPancreas: ↓ insulin and ↑ glucagon Platelets: stimulation of platelet aggregation β1 s Heart: positive chronotrope and inotrope Kidney: ↑ renin release Lipocytes: ↑ lipolysis β2 s Vasculature: vasodilation (specifically skeletal muscle vasculature) Lung: bronchodilation GI and GU: bladder and uterus relaxation Heart: positive inotrope and chronotrope Eye: ciliary muscle relaxation Lipocytes: ↑ lipolysis Pancreas: ↑ insulin release Liver: ↑ gluconeogenesis and glycogenolysis Cholinoreceptors: Parasympathetic System Receptor GPCR Class Locations and Major Functions M1 q CNS: excitatory in the CNSGlands: ↑ salivary, sweat, and stomach secretions M2 i Heart: negative chronotrope and ↓ contractility of atria M3 q Glands: ↑ salivary, sweat, stomach glands GI and GU: ↑ motility, ↑ bladder and uterus contraction Lung: bronchoconstriction Eye: ciliary and iris circular muscle contraction Dopaminergic Receptors Receptor GPCR Class Locations and Major Functions D1 s Kidney: renal vascular smooth muscle relaxation D2 i Brain: modulates neurotransmitter release Other G Protein-Coupled Receptors (Histamine and Vasopressin) Receptor GPCR Class Locations and Major Functions H1 q Glands; ↑ nasal and bronchial mucus secretion Lung: bronchoconstriction Skin: pruritus (itching), ↑ pain and irritation H2 s GI: ↑ gastric acid secretion V1 q Vasculature: vasoconstriction V2 s Kidney: antidiuretic, ↑ water permeability and reabsorption in the collecting tubules