2. effect of some drugs on blood pressure and.ppt manal
TRANSCRIPT
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8/2/2019 2. Effect of Some Drugs on Blood Pressure and.ppt Manal
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Effect of some drugs on blood
pressure and heart rate of
anesthetized rat
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Test the effect of the following drugs on
BP and HR, record your observation?
Vasopressin
Angiotensin
Histamine
Propranolol
Atenolol
Prazosin
Saline
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Effect of vasopressin on BP and HR
Observation: increased BP with decrease in the HR .
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Explain the effect of vasopressin on BP.
Vasopressin activates Vasopressin receptor type
1(V1) on blood vessels leading tovasoconstriction. VC PVR BP
The negative chronotropic effect is due to the
baroreceptor response to increased BP.
Does vasopressin have a therapeutic benefit?
It is used IV to control gastrointestinalbleeding e.g. esophageal varices
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Effect of angiotensin on BP and HR
Observation: angiotensin increases both BP and HR
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Explain the effect of angiotensin on BP
Angiotensin activates angiotensin receptors on blood
vessels vasoconstriction. VC PVR BP Angiotensin increases sympathetic nervous system
activity increases sympathetic discharge to the bloodvessels vasoconstriction
Suggest an experiment to prove your explanation?
Injection of angiotensin receptor
antagonist(e.g. losartan) will blockthe effect of angiotensin on BP
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Explain the effect of angiotensin on HR?
Angiotensin increases sympathetic nervoussystem activity increases sympatheticdischarge to the heart increased HR
Suggest an experiment to prove your explanation?
Injection of propranolol before
angiotensin
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Observation: propranolol abolishes the
effect of angiotensin on HR
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Does angiotensin has a therapeutic
benefit?
No
Angiotensin receptor blockers and convertingenzyme inhibitors are used for treatment ofhypertension
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Effect of histamine on BP and HR
Observation:
low dose histamine reduces BP
High dose histamine reduces BP and
increase HR
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Explain the effect of histamine on BP
Histamine activates H1 receptors in bloodvessels which leads to:
Vasodilation : By releasing endothelial-derived NO
Increased capillary permeability edema& decreased blood volume
Injection of H1 receptor antagonist(mepyramine) before histamine
Suggest an experiment to prove your explanation?
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Observation: mepyramine reverses the
effect of histamine on BP but not HR
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Explain the effect of histamine on HR
Histamine stimulates H2 receptors on Heart Cardiac stimulation (heart rate &SV)
Suggest an experiment to prove your explanation?
Injection of H2 receptor antagonist(ranitidine) before histamine
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Observation: ranitidine decrease the effect
of histamine on HR but not BP
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What is the therapeutic implication of this
experiment?
Anaphylactic shock
There is a massive release of histamine
1. VD & capillary permeability hypotension
2. Bronchospasm
H1 antagonists play a secondary role can noteasily overcome the effect of massive histaminerelease
Epinephrine is a physiological antagonist ofhistamine drug of choice for anaphylactic shock
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Effect of prazosin on BP and HR
Observation: It decreases blood pressure with slight increase in HR
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It is a selective competitive alpha 1 adrenoceptorantagonist
Blocks 1adrenoceptors
a.
Dilation of arterioles
PVRb. Dilation of veinsvenous returnCOP
Since the drug has no effect on beta receptors, lowering
of BP reflex tachycardia
Explain the effect of prazosin on BP
& HR
Suggest an experiment to prove your explanation?
Injection of a selective alpha 1 agonist(phenylephrine) before & after prazosin
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Observation: Prazosin abolishes the effect
of phenylephrine
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Effect of propranolol on BP and HR
Observations: Propranolol decreases both HR & BP
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What are the types of receptors blocked by
propranolol
Propranolol blocks both Beta 1 and beta 2adrenoceptors
Suggest an experiment to prove your answer
Inject a beta adrenoceptor agonist(isoprenaline) before and after propranolol
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Propranolol abolishes the effect of
isoprenaline on BP and HR
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Does propranolol have an effect on alpha
receptors? Inject phenylephrine (a selective alpha adrenoceptor agonist) before and
after propranolol
Propranolol doesnt alter the effect of phenylephrine
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Effect of nifedipine on BP and HR
Observation: nifedipine decreases BP with no effect on heart rate
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Explain the effect of nifedipine on BP &
HR
Nifedipine is a calcium channel blocker
It has a selective action on vasculature
It leads to arterial vasodilation, PVR andblood pressure
Eff f li d i i i bl d P &
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Effect of saline administration on blood Pressure &
Heart rate
Saline causes a transient increase in BP and HR
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Saline 0.9% is a crystalloid whose infusion in blood volume stroke volume
BP.
HR is attributed to Bainbridge reflex, forwhich the effective stimulus was an adequate
rise in central venous pressure The effect on BP & HR is transient because
H2O content freely travels outside the
vasculature. Can be used in transient treatment of
hypovolemic shock to replace fluids that havebeen lost .