CardiovascularStimulants

Question 1

What does epinephrine do locally? Systemically? What receptors is it specific for?

Answer 1

locally it is a vasoconstrictor. Systemically it will increase HR and CO. It will also decrease TPR by vasodilating skeletal muscles and high demand areas. No reflex inhibition of heart. Acts on A1, A2, B1, and B2 receptors.

Question 2

What will high dopamine dosage do? What will low dosage do?

Answer 2

at high doses (>10mcg/kg/min) dopamine will have A-agonist effect and incrase TPR and renal vasoconstriction

At low doses (<2) predominantly D1 action, renal and mesenteric vasodilation, improves GFR.

At moderate doses, D1 and B1, increase CO and vasodilates. Also increases NE release.

Question 3

What is dobutamine? What receptors is it specific for? What is its mechanism?

Answer 3

racemic mixture of B1-agonist, a1-antagonist and a1-agonist. Increases CO and SV without affecting HR. Decreases left ventricular filling pressures. Ultrashort duration.

Question 4

What is the mechanism behind alpha1 receptor signalling?

Answer 4

binding of alpha1 receptor triggers formation of IP3 and DAG, which increase intracellular Ca

Question 5

What is the mechanism of A2 receptor signaling?

Answer 5

A2 binding inhibits adenylyl cyclase, which decreases cAMP levels

Question 6

What is the mechanism of B1 receptor signaling?

Answer 6

B1 binding stimulates adenylyl cyclase, which increases cAMP

Question 7

What is the mechanism behind B2 receptor signaling?

Answer 7

B2 binding stimulates adenylyl cyclase, which increases cAMP. It also activates cardiac Gi under certain conditions

Question 8

What is the mechanism behind D1 and D5 receptor signaling?

Answer 8

D1 or D5 binding stimulates adenylyl cyclase, which increases cAMP

Question 9

What is the mechanism behind D2 receptor signaling?

Answer 9

binding of D2 decreases adenylyl cyclase, which reduces cAMP and increases K+ conductance across membrane, stabilizing it and making it harder to depolarize the cell.

Question 10

Which will increase cardiac output: epinephrine, norepinephrine, or both?

Answer 10

only epinephrine will increase CO.

Question 11

What is isoproterenol? What receptors is it specific for? What is its mechanism?

Answer 11

B1 and B2 agonist. It decreases TPR and BP, but HR dramatically increases, No reflex inhibition of heart. Used in cardiovascular emergencies.

Question 12

What is norepinephrine? What receptors is it specific for? What is its mechanism?

Answer 12

Norepinephrine is predominantly A1 mechanism, but also has vagus action, which decreases HR. This prevents it from increasing CO. It has action on A1, A2 and B1 receptors

Question 13

If epinephrine were given with an alpha-blocker, what change in BP would you expect?

Answer 13

a decrease in BP because the A1 activity of epinephrine will no longer have effects, but the B2 and B1 receptors will still work and create a parasympathetic effect on vasculature

Question 14

What effect will epinephrine have on renal blood flow? Renin levels?

Answer 14

epinephrine will restrict renal bloodflow, thus increase Renin production

Question 15

What is dopamine? What receptors is it specific for? What is its mechanism?

Answer 15

precursor of E and NE. acts on D1, B1 and A receptors depending on dose. GIven IV infusion, very short duration of action. At low doses, D1. At moderate dose (2-10 mcg/kg/min) D1 and B1. At high doses, alpha-agonist.

Question 16

What is phenylephrine? What receptors is it specific for? What is its mechanism?

Answer 16

A-agonist. Systemic arterial vasoconstriction increases BP, decreases HR and CO. Controls hypotension.

Question 17

What is ephedrine? What receptors is it specific for? What is its mechanism?

Answer 17

mixed sympathomimetic. Direct agonist at both A and B receptors. enhances NE release. Sustains BP. Increases HR and CO. Can cause fatal arrhythmia.

Question 18

What do M2 receptors do? How?

Answer 18

decelerate SA node and decrease atrial contractility in heart. Couples by Gi/Go. Inhibits Ach, decreasing caMP levels, activating K+ channels and inhibitng Ca channels. This hyperpolarizes neuron and inhibits it.

Question 19

What do M3 and M5 receptors do?

Answer 19

Gq coupling. Vasodilation and increase in intracellular Ca. synthesizes and releases EDRF in endothelium of vessels in heart brain and viscera.

Question 20

How do M3 receptors work?

Answer 20

couples Gq/11. Activates PLC, increasing IP3 and DAG, which increases Ca and PKC. This depolarizes and excites nuerons, activating PLD2, PLA2, and increases AA. Synthesis of NO, relaxing smooth muscle.

Question 21

What is atropine? What receptors is it specific for? What is its mechanism?

Answer 21

Non-selective antagonist of all muscarinic receptors. At low doses, blockade of presynaptic M1, decreases Ach release, causes decrease in HR.
At higher doses, progressive tachycardia due to blockade of M2 receptors on SA node. Only changes resting HR, has no effect on maximal HR. Can cause atropine blush, which is from dilation of cutaneous vessels. Used to reduce reflex vagal cardiac slowing.

Question 22

What effect does epinephrine have on systolic BP? Diastolic? Cardiac output? Pulse pressure? HR? TPR?

Answer 22

increases systolic. Almost no effect or decrease in diastolic. Pulse pressure increase. CO increased. HR increased. Decrease in TPR.

Question 23

What effect does norepinephrine have on systolic BP? Diastolic? Cardiac output? TPR?

Answer 23

increases both BP. Small pulse pressure increase. Decrease in CO. Reflexive decrease in HR. Increase in TPR.

Question 24

What effect does isoproterenol have on Systolic BP? Diastolic? HR?, TPR?

Answer 24

systolic increase. Diastolic decrease. (overall decrease in pressure). Widened pulse pressure. Decrease in TPR. Reflex increase in HR.

Question 25

What receptor will low dose dopamine act on?

Answer 25

predominantly D1 action. will improve GFR. Intermediate doses will also act on B1

Question 26

What receptor will high dose dopamine act on?

Answer 26

alpha-agonism. Increases TPR and decreases GFR.