lecture 7

Question 1

Define what a drug does to receptors if its an agonists and antagonist

Answer 1

agonists; drugs will stimulate the receptors and mimic the parasympathetic nervous system
antagonist; drug which blocks the receptors

Question 2

For parasympathometics list what it does

main types

Answer 2

parasympathometics; mimics what ACh does
there are 3 main types which are;
-direct acting esters e.g carbachol and methacholine (have longer half life than ACh which helps with clinical use this is because they are resistant to the enzyme which breaks ACh down) these drugs also act upon the main systems eg heart, GIT etc.
want to highen rest and digest
-alkaloids
not commonly used in vet medicine
they are agnostics so they are activators
e.g muscarine
important in toxics
-indirect, AChE, inhibitors
very common
they don’t care about the receptor for ACh
they stop the hydrolysis of ACh
its useful for when a dog become exposed to a cattle drip it the indirect AChE inhibitors which kills it

Question 3

List the clinical uses of parasympathometics

Answer 3

clinical uses parasympathometics
-urinary bladder atony (muscle has lost its strength) in cats (urolithiasis, bladder stones)
-rumen atony
-colic and impaction of the intestinal tract
-retained placenta/ still birth
-glaucoma (vision is lost due to damage to the optic nerv)
-anti-curare (opposite of muscle relaxant) & myasthenia (weakness of certain muscles) like symptoms in dogs
if a drug produces a lot of ACh it will reverse the effects of muscle relaxin

Question 4

If a cat comes in with a very low heart rate wha drug will you administered and why

Answer 4

if your cats hr is dropping give the cat atropin which will block the parasympathetic system and stimulate the sympathetic nervous system which will increase the HR

Question 5

Which of the following statements in incorrect in relation to typical application of eye ointments containing pilocarpine? pilocarpine causes?

a. contraction of circular virus muscles via alpha-receptors
b. contraction of circular iris muscle via muscarinic receptors
c. loss of accomodation
d. pupillary dilation overall

Answer 5

d. pupillary dilation overall

it causes the eyeball to constrict

Question 6

For which of the following conditions would you recommend the use of muscarinic receptors agonists such as carbachol or bethenecol

a. a dog wth peptic ulcers and increase acid secretion
b. a cat with increased bronchial secretions and asthma
c. a horse with increased plumbery secretions and oedema
d. a dog with urinary bladder stones but with a mechanism blockage at the neck of urinary blocker
e. explosion of a retained placenta following farrowing in a pig

Answer 6

e. explosion of a retained placenta following farrowing in a pig

Question 7

Cholinomimetic agents are self for their ability to modulate parasympathetic autonomic activity. One important groups of these cholinergic agents are acetylcholinesterase inhibitors? which of the following is an irreversible acetylcholinesterase inhibitor and therefore poisonous?

a. physostigmine
b. neostigmine
c. pyridostigmine
d. edrophonium
e. o-isopropyl-methylphosphono, fluoridate, sarin

Answer 7

e. o-isopropyl-methylphosphono, fluoridate, sarin

Question 8

For which of the following clinal conditions would you NOT use neostigmine as a drug?

a. intestinal smooth muscle paralysis/atony
b. induction of mitosis tp drain aqueous humour in glaucoma
c. myasthenia graves-auto immunity against nicotinic receptors
d. paralysis of smooth muscles of the unrinary bladder and a patent urinary tract
e. organophosphate poisoning

Answer 8

e. organophosphate poisoning

Question 9

A dog that was treated with a liquid organophosphate parasiticide, later the dog show several signs including; excessive panting, salivation and trouble walking. his muscles suddenly contracted and his whole body appears rigid. The dog was taken to the hospital and the examination revealed, excessive salivation, ataxia, constricted pupils an muscle fasciculation. The rectal temp was 39.5C, HR 60 bpm and there was frequent intestinal movement via auscultation with hypersensitivity to touch and sound. Treatment was initiated immediately and this dog was released from hospital 48 hr after the initial admission.

• what receptor subtypes are involved?
• what are the organ function specific effects?
• Treatment options and rationales

Answer 9

-what receptor subtypes are involved?
M2, M3

-what are the organ function specific effects?
lung function and respiration
smooth muscle tone in the fungus of urinary bladder
The organophsophate will act a as an inhibitor of the enzyme ACHe, which is the important of the inactivation of Ach, there will be an excess of parasympathetic effects like GIT there will be an increase in moltity and relaxation of the sphincters
Eyes will constrict

-Treatment options and rationales
Use atropine to block muscarinic receptors but this is only useful if this applied early before the bond between the organophosphate and acetlcholinesterase becomes irreversible