2. Effect of Some Drugs on Blood Pressure and.ppt Manal

8/2/2019 2. Effect of Some Drugs on Blood Pressure and.ppt Manal

1/26

Effect of some drugs on blood

pressure and heart rate of

anesthetized rat


2/26

Test the effect of the following drugs on

BP and HR, record your observation?

Vasopressin

Angiotensin

Histamine

Propranolol

Atenolol

Prazosin

Saline


3/26

Effect of vasopressin on BP and HR

Observation: increased BP with decrease in the HR .


4/26

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


5/26

Effect of angiotensin on BP and HR

Observation: angiotensin increases both BP and HR


6/26

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


7/26

Explain the effect of angiotensin on HR?

Angiotensin increases sympathetic nervoussystem activity increases sympatheticdischarge to the heart increased HR


Injection of propranolol before

angiotensin


8/26

Observation: propranolol abolishes the

effect of angiotensin on HR


9/26

Does angiotensin has a therapeutic

benefit?

No

Angiotensin receptor blockers and convertingenzyme inhibitors are used for treatment ofhypertension


10/26

Effect of histamine on BP and HR

Observation:

low dose histamine reduces BP

High dose histamine reduces BP and

increase HR


11/26

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



12/26

Observation: mepyramine reverses the

effect of histamine on BP but not HR


13/26

Explain the effect of histamine on HR

Histamine stimulates H2 receptors on Heart Cardiac stimulation (heart rate &SV)


Injection of H2 receptor antagonist(ranitidine) before histamine


14/26

Observation: ranitidine decrease the effect

of histamine on HR but not BP


15/26

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


16/26

Effect of prazosin on BP and HR

Observation: It decreases blood pressure with slight increase in HR


17/26

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


Injection of a selective alpha 1 agonist(phenylephrine) before & after prazosin


18/26

Observation: Prazosin abolishes the effect

of phenylephrine


19/26

Effect of propranolol on BP and HR

Observations: Propranolol decreases both HR & BP


20/26

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


21/26

Propranolol abolishes the effect of

isoprenaline on BP and HR


22/26

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


23/26

Effect of nifedipine on BP and HR

Observation: nifedipine decreases BP with no effect on heart rate


24/26

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 &


25/26

Effect of saline administration on blood Pressure &

Heart rate

Saline causes a transient increase in BP and HR


26/26

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 .

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2. Effect of Some Drugs on Blood Pressure and.ppt Manal