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![Explanation for acetylcholine reversal
• Atropine injection A parasympatholytic blocks muscarinic receptors. It blocks
the effect of small dose of Ach.
• Ach injection [big dose] Stimulates nicotinic receptors Nn after muscarinic
receptors have been blocked by atropine ABP
• Due to activation of Nn at :
• Adrenal medulla release epinephrine BP
• Autonomic ganglia release of catecholamines from post-synaptic adrenergic nerve endings
BP
• The BP by Ach [big dose] after muscarinic receptor block [by atropine]
Ach reversal](https://image.slidesharecdn.com/practicalpharmacology2ndupload-151228191412/75/Practical-pharmacology-CNS-46-2048.jpg)
Uploaded byHazem Abo Shousha
Practical pharmacology CNS
This document discusses the effects of various drugs on blood pressure and heart rate. It begins by explaining that blood pressure is determined by cardiac output and peripheral vascular resistance. It then examines the effects of drugs that act on adrenoreceptors, including norepinephrine, epinephrine, isoproterenol, phenylephrine, and drugs that block various receptors. The effects of acetylcholine and drugs that modify its effects are also discussed. Experiments are proposed to prove the mechanisms of action of the various drugs.
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Similar to Practical pharmacology CNS
Practical pharmacology CNS
- 1. 2ND YEAR MEDICALSTUDENTS MODULE IX BY DR. HAZEM ABO SHOUSHA
- 2. Main rules •ABP: pressureof blood on arterial wall
- 3. ABP= COP XPVR COP= HR X SV Main rules
- 4.
- 5. Main rules β1 AgonistM2 blocker β1 blocker M2 agonist HEART RATE
- 6.
- 7. Main rules BLOOD PRESSURE(Bl.V) VC α1 agonist β2 blocker VD α1 blocker β2 agonist M3 agonist
- 8.
- 9.
- 11. Observation: increased ABPwith minimal effect on HR, which increases only with high doses Explanation of effect of NE on ABP & HR: NE acts mainly on 1 receptors vasoconstriction PVR With higher doses of NE, it activates also cardiac 1 receptors some increase in the heart rate
- 12.
- 14. What is theeffect of Prazosin on ABP and HR? •it blocks 1 adrenoceptors vasodilationPVRABP •ABP slight reflex tachycardia
- 15. Noradrenaline cause veryminimal in HR β1 stimulation minimal in BP
- 16.
- 18. Observation: ABP& HR late The ABP before returning to base line level Explanation of the effect of epinephrine on HR & ABP Epinephrine stimulates 1 , 1, 2 adrenoceptors Beta receptors are more sensitive to the effect of epinephrine On heart: 1 activation +ve inotropic & chronotropic effects COP leading to increased ABP On BV : - 1 activation vasoconstriction PVR. - 2 activation vasodilatation PVR
- 19. •The net effectof these two opposing effects (1 & 2 ) on bl.v is an in PVR (1 wins at 1st ) •At High concentration: EPI stimulates 1 •At Low concentration: EPI stimulates 2
- 20. AdrenalineNoradrenalineparameters More increaseMild orno increaseHeart rate Less increase than noradrenaline More increaseBlood pressure BP decreases before reaching base line Reach base line directlyBP before Base line
- 21. β1 blocker Cardioselective betablocker ATENOLOL
- 23. Observation: blocking 1receptors by atenolol blocks the effect of epinephrine on HR & decreases the effect on ABP
- 24. block alpha1 &beta1 receptors & then inject epinephrine
- 25. EPINEPHRINE REVERSAL: The pressereffect of epinephrine is reversed due to 1 & 1 blockade, leaving the 2 vasodilating effect acting ABP
- 26. β1 + β2blocker Non-selective beta blocker PROPRANOLOL
- 27. How to confirmthe cause of epinephrine reversal? No epinephrine reversal since propranolol blocks not only cardiac 1 receptors but also vascular 2 receptors
- 28. What is theeffect of propranolol on ABP and HR?
- 29. Propranolol mechanism asantihypertensive: 1-Block β1 in heart so low COP BP 2- central sympathetic discharge BP 3- Block β1 in kidney Renin BP 4- resetting of Baroreceptors BP 5- Block β2 presynaptic NE release BP
- 30. β1 + β2agonist Non-selective beta agonist ISOPRENALINE
- 32. Observation: • Isoprenaline increasesHR • Isoprenaline initially decreases ABP. • As HR reaches its maximum increase, ABP shows minimal increase before returning to normal Explanation for the effect of isoprenaline on HR & ABP • Isoprenaline activates mainly beta adrenoceptor • It activates cardiac 1 receptors leading to increase in HR & force of contraction (which increases COP) • Activation of 2 receptors—Vasodilation decrease in PVR • The net effect of the two factors (COP & PVR) is a decrease in blood pressure initially. • However, when force of contraction is markedly elevated, the increase of COP overcomes the effect of decrease in PVR and thus ABP starts to increase.
- 33. Design an experimentto prove the explanation for the effect of Isoprenaline on HR & ABP
- 34. Observation: atenolol abolishesthe effect of isoprenaline on HR The initial ABP-lowering effect of isoprenaline is maintained, while its pressor effect is abolished
- 35. PROPRANOLOL FOLLOWED BYISOPRENALINE Observation: Propranolol blocks 1 & 2 receptors thus abolishes the effect of isoprenaline on ABP
- 36. 1 agonist selective Alphaagonist PHENYLEPHRINE
- 37. Observation: Small dose phenylephrineleads to slight increase in ABP with no effect on HR High dose phenylephrine increases markedly ABP with decrease in the HR ( reflex bradycardia)
- 38. Explanation of theeffect of phenylephrine on ABP & HR •Activation of 1 receptors vasoconstrictionPVR •High dose of phenylephrine marked elevation of ABP reflex in sympathetic activity. Parasympathetic activity will take the upper hand HR
- 39. prove the explanationof the effect of phenylephrine on HR and ABP Observation: prazosin abolishes the effect of phenylephrine on ABP & reflex bradycardia disappears
- 40. prove that reflexbradycardia is due to relative increase in parasympathetic activity Observation: decreased HR is abolished by atropine despite of elevation of ABP
- 41. Nicotinic Nn , Nm ACETYLCHOLINE( Ach ) Muscarinic M1 , M2 ,M3
- 43. Observation: small doses ofacetylcholine lower only ABP Higher doses produce both in the HR & more significant lowering of ABP Explanation for the effect of acetylcholine on HR and ABP •on heart: M2 activation - ve chronotropic effect COP •on BV: endothelial cells M3 activation release of NO from vascular endothelial cells vasodilatation PVR • Decrease in heart rate & decrease in PVR lead to ABP
- 44. Inject ATROPINE &then test the effect of ACETYLCHOLINE
- 45. ACETYLCHOLINE REVERSAL 1. Injecta test dose of Ach 2. Inject atropine 3.Inject the same dose of acetylcholine 4.Inject a dose of Ach which is 10 times the test dose
- 46. Explanation for acetylcholinereversal • Atropine injection A parasympatholytic blocks muscarinic receptors. It blocks the effect of small dose of Ach. • Ach injection [big dose] Stimulates nicotinic receptors Nn after muscarinic receptors have been blocked by atropine ABP • Due to activation of Nn at : • Adrenal medulla release epinephrine BP • Autonomic ganglia release of catecholamines from post-synaptic adrenergic nerve endings BP • The BP by Ach [big dose] after muscarinic receptor block [by atropine] Ach reversal
- 47. oAch reversal by: Nn receptors oEPI reversal by : β2 receptors
- 48. Reversible anticholinesterase So Ach‘ ’augment Ach effect ‘ ’ NEOSTIGMINE
- 49. prove the mechanismof action of neostigmine