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Flashcards in Drugs affecting Vasculature Deck (25):

What causes contraction of vascular smooth muscle?

GPCR coupled to Gq/11 stimulates the SR to release Ca, Ca induced Ca release and formation of Ca-CaM which activates MLCK which phosphorylates MLC and causes contraction


What causes relaxation of vascular smooth muscle?

cGMP activates PKG which activates MLC phosphatase, dephosphorylating MLC and causing relacation


How do organic nitrates cause relaxation?

Stimulate guanylate cyclase which phosphorylates GTO to cGMP activating protein kinase G and causing relocation


How to vasodilating substances such as bradykinin and NO work?

Increase cellular calcium, increasing the level of Ca-CaM which stimulates eNOS and the formation of NO, activating guanylate cyclase and hyper polarising the cell causing relaxation


Describe the effects of organic nitrates

-venorelaxation at small doses
-arteriolar dilatation higher doses
-increased coronary blood flow


Describe the effects of GTN

Extensive first pass metabolism and short acting


Describe the effects of isosorbide mononitrate

Longer acting
resistant to first pass metabolism


How does endothelin work?

Through ETa receptor to cause contraction


What does the RAAS system regulate?

Sodium excretion
Vascular tone


What causes Renin release?

Increased renal sympathetic nerve activity

Decreased renal perfusion pressure

Decreased glomerular filtration rate


Describe the effects of ACE inhibitors?

1. block the conversion of angiotensin I to angiotensin II meanwhile activating bradykinin (vasodilator)
2. no effect on cardiac contractility- CO increase as a result of decreased TPR
3. reduce release of aldosterone by the kidneys
4. greatest effect in brain, heart, kidneys
5. hypotension and dry cough


How do AT1 receptor antagonists work?

Block the agonist action of angiotensin II receptors in a competitive manner

Dont inhibit the metabolism of bradykinin


What are the clinical uses of AT1 receptor antagonists and ACE inhibitors

hypertension= benefit from
1) reduced TPR and MABP and
2) possible suppression of proliferation of smooth muscle cels in the media of resistance vessels

cardiac failure
1) decrease vascular resistance improving perfusion
2) increase excretion of Na and H20
3) regression of LVH

Post MI


What is the clinical use of B clockers?

Treatment of angina pectoris (particularly B1 blockers)

Treatmment of hypertension

Treatment of heart failure


How do B blockers work in angina?

decreased myocardial O2 requirement

counter elevated sympathetic activity associated with ischaemic pain

increase the time for diastole


What is the function of B blockers in heart failure?

in combo with other drugs to suppress adverse effects associated with elevated activity of the sympathetic nervous system and RAAS

cause reflex activity


How do Ca antagonists work?

Calcium antagonists block, or prevent the opening of L-type channels in excitable tissues
clinically useful Ca blockers act preferentially or solely with L type Ca channels in the hears and smooth muscle


What do L-type calcium antagonist mediate?

upstroke of the AP in the SA and AV node

reduce the rate of conduction through the AV node
reduce the ventricular force of contraction in phase 2


Describe verapamil

Relatively selective for cardiac L-type channels
Avoid in heart failure


Describe Amlodipine

Dihydropiridine compound- relatively selective for smooth muscle type L-channels

Preferred for minimisation of unwanted effects upon cardiac muscle

Systolic hypertension


Describe diltiazem

Intermediate selectivity


How do potassium channel openers work?

Open ATP-modulated K+ channels in vascular smooth muscle by antagonising intracellular ATP
Cause hyperpolarisating which switches of L-type channels
act potentially and primarily on arterial smooth muscle


Describe minoxidil

Last resort in severe hypertension
Counteract reflex tach with B-blocker
Counteract salt and water retention with diuretic


Describe nicorandil



How do a1-adrenoreceptors work?

Cause vasodilatation, reducing MABP
Prazosin and doxasosin- competitive antagonists
symptomatic relief in prostatic hyperplasia
may get dizzy