This presentation deals with the in-depth analysis of various cardiac stimulants & depressants both directly & indirectly acting on frog's heart. Also, includes a nice quiz, a good exercise for the grey cells of the brain at the end of the presentation.

1. CAL  Effect of drugs on
frog’s heart

4. Following parameters noted
1. Force of contraction 
amplitude (N, ↑, ↓)
2. Tone (N, ↑, ↓)
3. Heart rate (bpm)

6. Addition of unknown drug (UD) to frog’s heart
↓ ↓
↑ HR, tone, amplitude ↓ HR, tone, amplitude
↓ ↓
UD  Cardiac stimulant UD  Cardiac depressant
↓ ↓
Ppnl (0.2 ml) inj. foll. By UD Atr (0.2 ml) inj. foll. by UD
↓ ↓ ↓ ↓
No effect ↑ tone No effect ↓ tone
↓ ↓ ↓ ↓
UD - Indir. UD - Directly UD – Indir. UD -Directly
Acting cs acting cs acting cd acting cd
(E,NE, Iso) (CaCl2) (Ach) (KCl)

7. Regulation of the heart
Dominant tone = parasympathetic
Sympathetic
Increases heart rate
and contractility via
beta-1 and 2
(primarily beta-1)
Parasympathetic
Decreases heart
rate and atrial
contractility via M2

8. PREDOM

14. 1. Ach Cardiac effects  ↓ impulse formation in
SAN by ↓ the rate of diastolic depolarization (↓
HR) & ↑ PR interval (Time from SAN to AVN)
2. Atr Cardiac eff.  ↑ HR & AV conduction velocity
by blocking the effects of the vagus nerve on sa,av
• Low i.v. atropine  paradoxical slowing of HR
(stimulation of the vagal motor nucleus in the brain
stem). After full dose  heart rate ↑

15. CVS eff. Of NE, E, Isoprenaline
• NE  Activation of α1 receptors (V.c. & ↑ TPR)
Reflex bradycardia if blood pressure increases
sufficiently to activate the baroreceptor reflex
• E  ↑ SBP but can ↑ or ↓ DBP
• Isoproterenol  Activates β1 and β2 receptors
• Propranolol  Blockade of β1 receptors

16. Baroreceptor reflex

19. Dopamine
• Low doses (< 2 μg/kg per min)  D1 dopaminergic
receptors in renal, mesenteric, and coronary
vascular beds. (vasodilation)
• Moderate dose (2–10 μg/kg per min)  β1 recept.
• Higher dose (10 μg/kg per min)  α1 receptors

20. Adrenaline
Uses (ABCD)
1. Anaphylactic shock (DOC)  0.5 mg (0.5 ml of 1
in 1000 solution for adult) i.m.
2. Bronchial asthma
3. Cardiac arrest  10 ml of 1:10000 i.v.
4. Control of local bleeding  Adr 1 in 10,000
5. During LA combined with Lignocaine (1:50,000 or
1:2,00,000)

21. Acetylcholine
• Choline ester of acetic acid
• Uses
1. During cataract surgery (Miosis) NO topical
2. Diagnostic coronary angiography  intracoronary
injection to cause coronary artery spasm
3. Vasospastic angina pectoris, however,
intracoronary injection of acetylcholine can
provoke a localized vasoconstrictive response,
and this helps establish the diagnosis of
vasospastic angina

22. Atropine & Scopolamine (t.a.)
• t1/2  2 hrs (oral route)
• After topical ocular administration, they have
longer-lasting effects because they bind to
pigments in the iris that slowly release the drugs.
• People with darker irises bind more atropine and
experience a more prolonged effect than do people
with lighter irises. The ocular effects gradually
subside over several days.
• “dry as a bone, blind as a bat, red as a beet, and
mad as a hatter.” Atr. toxicity

23. Effects
• Ocular eff.  Myd. + cycloplegia
• Cardiac eff.  ↑ HR & AV conduction velocity by
blocking the effects of the vagus nerve on SAN,AVN
Low i.v. atropine  paradoxical slowing of HR
(stimulation of the vagal motor nucleus in the brain
stem). After full dose  heart rate ↑
• Resp. tract eff.  bronchial smooth muscle
relaxation and bronchodilation, inhibitors of
secretions in the upper and lower respiratory tract.

24. Indications
• Ocular Indications  mydriasis (facilitate peripheral
retina), cycloplegia (refractive errors), iritis and
cyclitis (↓ muscle spasm and pain)
• Cardiac Indications  Sinus bradycardia after MI.
AV block to ↑ AV conduction velocity
• Respiratory Tract Indications  ↓ salivary and
respiratory secretions & prevent airway obstruction
in patients who are receiving general anaesthetics.
Glycopyrrolate is often used for this purpose today

25. • GIT Indications  Relieve intestinal spasms & pain
• UT indications  Relieve urinary bladder spasms in
persons with overactive bladder.
• CNS Indications  A transdermal formulation of
scopolamine can be used to prevent motion
sickness (blocking Ach neurotransmission from the
vestibular apparatus to the vomiting center in the
brain stem). Also, PD.
• Other Indications
1. Prevent muscarinic side effects when chE
inhibitors are given to patients with myasthenia
gravis.
2. Reverse the muscarinic effects of cholinesterase
inhibitor overdose.

26. Atropine
Uses (ATROPA)
1. As mydriatic-cycloplegic in refraction error
testing, fundoscopy, iridocyclitis
2. Traveller’s diarrhea
3. Rapid onset mushroom poisoning
4. Organophospohorous poisoning
5. Preanaesthetic medication
6. Arrhythmias (brady-arrhythmias)

27. Propranolol (Uses  THAPPAD)
1. Thyrotoxicosis & Tremors
2. HTN & Hypertrophic cardiomyopathy
3. Angina & Acute MI
4. Prophylaxis of migraine
5. Phaeochromocytoma (along with alpha blockers)
6. Anxiety & Arrhythmias
7. Dissecting aortic aneurysm
8. Digitalis toxicity

28. MUSCARINIC effects (OP poisoning)
M  Miosis
U  Urination
S  Secretions ↑ (salivation, lacrimation, sweating)
C  Cardiac contraction & conduction slows
A  Abdominal cramps
R  Redn. In i.o.t. esp. in glaucoma
I  ↑ GI motility
N  NO dependent vasodilatation
I  Inc. secretion from GIT & tracheobronchial tract
C  Constriction of tracheobronchial tract

29. Adverse effects of Atropine
(DHATURA)
1. Dry mouth, difficulty in swallowing & speaking
2. Hot dry skin & hypotension
3. Accommodation paralysis (blurring of near vision)
4. Tachycardia
5. Urinary retention & fecal retention (constipation)
6. Respiratory depression
7. Ataxia & acute congestive glaucoma may
precipitate

30. Adverse effects of beta blockers
(BBC Loses Viewers in Rochedale)
• Bradycardia
• Bronchoconstriction
• Claudication
• Lipids (profile altered)
• Vivid dreams & nightmares
• Negative ionotropic action
• Reduced sensitivity to hypoglycemia

31. Contraindications of Propranolol
• Don’t Prescribe Him Propranolol
1. Diabetes mellitus
2. Pulmonary diseases (Asthma, COPD)
3. Heart block, bradycardia
4. Prinzmetal’s angina
5. Peripheral vascular disease

32. Review Questions

33. Q.1. 1. A 3-year-old child has swallowed the contents
of 2 bottles of a nasal decongestant whose primary
ingredient is a potent, selective α-adrenoceptor
agonist drug. Which of the following is a sign of α-
receptor activation that may occur in this patient?
(A) Bronchodilation
(B) Cardiac acceleration (tachycardia)
(C) Pupillary dilation (mydriasis)
(D) Renin release from the kidneys
(E) Vasodilation of the splanchnic vessels

34. Q.2. Ms Green is a 60-year-old woman with poorly
controlled hypertension of 170/110 mm Hg. She is to
receive minoxidil. The active metabolite of minoxidil
is a powerful arteriolar vasodilator that does not act
on autonomic receptors. Which of the following
effects will be observed if no other drugs are used?
(A) Tachycardia and increased cardiac contractility
(B) Tachycardia and decreased cardiac output
(C) Decreased mean arterial pressure and decreased
cardiac contractility
(D) Decreased mean arterial pressure and increased
salt and water excretion by the kidney
(E) No change in mean arterial pressure and
decreased cardiac contractility

36. Q.3. Full activation of the sympathetic nervous
system, as in the fight-or-flight reaction, may occur
during maximal exercise. Which of the following
effects is likely to occur?
(A) Bronchoconstriction
(B) Increased intestinal motility
(C) Decreased renal blood flow
(D) Miosis
(E) Decreased heart rate (bradycardia)

37. Q.4. Nicotinic receptor sites do not include which
one of the following sites?
(A) Bronchial smooth muscle
(B) Adrenal medullary cells
(C) Parasympathetic ganglia
(D) Skeletal muscle end plates
(E) Sympathetic ganglia

38. Q.5. Which one of the following is the
neurotransmitter agent normally released in the
sinoatrial node of the heart in response to a blood
pressure increase?
(A) Acetylcholine
(B) Dopamine
(C) Epinephrine
(D) Glutamate
(E) Norepinephrine

40. Q.6. A 30-year-old woman undergoes abdominal
surgery. In spite of minimal tissue damage, complete
ileus (absence of bowel motility) follows, and she
complains of severe bloating. She also finds it
difficult to urinate. Mild cholinomimetic stimulation
with bethanechol or neostigmine is often effective in
relieving these complications of surgery. Neostigmine
and bethanechol in moderate doses have
significantly different effects on which one of the
following?
(A) Gastric secretion
(B) Neuromuscular end plate
(C) Salivary glands
(D) Sweat glands
(E) Ureteral tone

41. Q.7. Ms Brown has been treated for myasthenia
gravis for several years. She reports to the
emergency department complaining of recent onset
of weakness of her hands, diplopia, and difficulty
swallowing. She may be suffering from a change in
response to her myasthenia therapy, that is, a
cholinergic or a myasthenic crisis. Which of the
following is the best drug for distinguishing between
myasthenic crisis (insufficient therapy) and
cholinergic crisis (excessive therapy)?
(A) Atropine
(B) Edrophonium
(C) Physostigmine
(D) Pralidoxime
(E) Pyridostigmine

42. Q.8. A crop duster pilot has been accidentally
exposed to a high concentration of a highly toxic
agricultural organophosphate insecticide. If
untreated, the cause of death from such exposure
would probably be
(A) Cardiac arrhythmia
(B) Gastrointestinal bleeding
(C) Heart failure
(D) Hypotension
(E) Respiratory failure

43. Q.9. Actions and clinical uses of muscarinic
cholinoceptor agonists include which one of the
following?
(A) Bronchodilation (asthma)
(B) Improved aqueous humor drainage (glaucoma)
(C) Decreased gastrointestinal motility (diarrhea)
(D) Decreased neuromuscular transmission and
relaxation of skeletal muscle (during surgical
anesthesia)
(E) Increased sweating (fever)

44. Q.10. Which of the following is the primary second-
messenger process in the contraction of the ciliary
muscle when focusing on near objects?
(A) cAMP (cyclic adenosine monophosphate)
(B) DAG (diacylglycerol)
(C) Depolarizing influx of sodium ions via a channel
(D) IP3 (inositol 1,4,5-trisphosphate)
(E) NO (nitric oxide)

45. Q.11. Probable signs of atropine overdose include
which one of the following?
(A) Gastrointestinal smooth muscle cramping
(B) Increased heart rate
(C) Increased gastric secretion
(D) Pupillary constriction
(E) Urinary frequency

46. Q.12. Accepted therapeutic indications for the use of
antimuscarinic drugs include all of the following
except
(A) Atrial fibrillation
(B) Motion sickness
(C) Parkinson’s disease
(D) Postoperative bladder spasm
(E) To antidote parathion poisoning

47. Q.13. A 7-year-old boy with a previous history of bee
sting allergy is brought to the emergency department
after being stung by 3 bees. If this child has signs of
anaphylaxis, what is the treatment of choice?
(A) Diphenhydramine (an antihistamine)
(B) Ephedrine
(C) Epinephrine
(D) Methylprednisolone (a corticosteroid)
(E) Phenylephrine

48. Q.14. A 65-year-old woman with long-standing
diabetes mellitus is admitted to the ward from the
emergency department, and you wish to examine
her retinas for possible changes. Which of the
following drugs is a good choice when pupillary
dilation—but not cycloplegia—is desired?
(A) Isoproterenol
(B) Norepinephrine
(C) Phenylephrine
(D) Pilocarpine
(E) Tropicamide

49. Q.15.An anesthetized dog is prepared for recording
blood pressure and heart rate in a study of a new
blocking drug. Results show that the new drug
prevents the tachycardia evoked by isoproterenol?
Which of the following standard agents does the
new drug most resemble?
(A) Atropine
(B) Hexamethonium
(C) Phentolamine (an α blocker)
(D) Physostigmine
(E) Propranolol (a β blocker)

50. Q.16. Your new 10-year-old patient has asthma, and
you decide to treat her with a β2 agonist. In
considering the possible drug effects in this patient,
you would note that β2 stimulants frequently cause
(A) Direct stimulation of renin release
(B) Hypoglycemia
(C) Increased cGMP (cyclic guanine monophosphate)
in mast cells
(D) Skeletal muscle tremor
(E) Vasodilation in the skin

51. Q.17. A patient is to receive epinephrine. She has
previously received an adrenoceptor-blocking agent.
Which of the following effects of epinephrine would
be blocked by phentolamine but not by metoprolol?
(A) Cardiac stimulation
(B) Increase of cAMP in fat
(C) Mydriasis
(D) Relaxation of bronchial smooth muscle
(E) Relaxation of the uterus

52. Q.18. When given to a patient, phentolamine blocks
which one of the following?
(A) Bradycardia induced by phenylephrine
(B) Bronchodilation induced by epinephrine
(C) Increased cardiac contractile force induced by
norepinephrine
(D) Miosis induced by acetylcholine
(E) Vasodilation induced by isoproterenol

53. Q.19. A 56-year-old man has hypertension and an
enlarged prostate, which biopsy shows to be benign
prostatic hyperplasia. He complains of urinary
retention. Which of the following drugs would be the
most appropriate initial therapy?
(A) Albuterol
(B) Atenolol
(C) Metoprolol
(D) Prazosin
(E) Timolol

55. Q.20. Which of the following agents does the new
drug most closely resemble?
(A) Atenolol
(B) Atropine
(C) Labetalol
(D) Phenoxybenzamine
(E) Propranolol

56. Thank you