Lecture 14-16 - Scrogin - Adrenergics (Receptors) Flashcards
What are the 5 adrenergic receptor sub-types we should know?
Alpha 1 and 2
Beta 1 and 2
Dopamine 1
Where are alpha-1 receptors found?
pupillary dilator muscle and most vascular smooth muscle
Where are alpha-2 receptors found?
Adrenergic and Cholinergic nerve terminals (pre-synaptic)
Where are dopamine-1 receptors found?
Renal and other splanchnic blood vessels
Where are beta-1 receptors found?
heart and JG (juxtaglomerular) cells
Where are beta-2 receptors found?
Respiratory/Uterine/Vascular smooth muscle
Somatic motor cholinergic nerve terminals (voluntary muscle)
What are the actions of dopamine-1 receptors?
relaxation/decreased resistance of renal/splanchnic blood vessels
What are the actions of alpha-1 receptors on the pupillary dilator muscle?
Mydriasis (contraction)
What are the actions of alpha-1 receptors on vascular smooth muscle?
Vasoconstriction (increased vascular resistance)
What are the actions of alpha-2 receptors on adrenergic/cholinergic nerve terminals?
Inhibit NT release
*you can also get some vasoconstriction
What are the 2 actions of beta-1 receptors on the heart and where specifically in the heart do they target?
Stimulate HR (chronotropy in SA Node pacemakers)
Increase force (contractility in ventricle myocytes)
What are the actions of beta-1 receptors on JG cells?
Stimulate renin release
What are the actions of beta-2 receptors on respiratory/uterine/vascular smooth muscle?
Relaxation (bronchodilation, increased blood flow via vasodilation, etc.)
It regulates the degree of airway constriction and peripheral vascular resistance
What are the actions of beta-2 receptors on somatic motor nerve terminals (voluntary muscle)?
Stimulates NT release and causes tremor
Alpha-1 receptors are coupled to what signaling pathway?
Phospholipase C via G-alpha-q/11 to increase IP3 and DAG
What is the mechanism of effect for vasoconstriction mediated by alpha-1 receptors?
Ligand activates G-alpha-q –> activate PLC –> PIP split into IP3 and DAG
IP3 binds IP3 receptor and gives Ca2+ release which binds calmodulin and activates myosin light chain kinase
What is the mechanism of effect for inhibited NT release mediated by alpha-2 receptors?
Coupled to G-alpha-i –> inhibits adenylyl cyclase –> dec cAMP –> dec PKA activation –> inhibit Ca2+ release/influx –> dec NE release
What is the mechanism of effect for + chronotropy mediated by beta-1 receptors?
Coupled to G-alpha-s –> activates adenylyl cyclase –> inc cAMP –> PKA activation –> phosphorylate Ca2+ channels –> inc inward Ca2+ current and get faster nodal cell depolarization to firing threshold (faster process and lower threshold)
What is the mechanism of effect for + intotropy mediated by beta-1 receptors?
Inc cAMP –> PKA activation –> inc phosphorylation of LTCC –> larger trigger for Ca2+ release from SR
*Trigger Ca2+ also enters SR which increases SR storage and gives larger Ca2+ efflux in the next round
What is the mechanism of effect for smooth muscle relaxation mediated by beta-2 receptors?
cAMP activates PKA which phosphorylates and inactivates MLCK which reduces its affinity for Ca2+-calmodulin and gives decreased phosphorylation of MLC
Get less smooth muscle conraction
What is the mechanism of effect for peripheral vasoconstriction mediated by alpha-2 receptors?
Inhibition of PKA leads to activation of MLCK and vascular smooth muscle constriction
