ANS and Parasympathetic Pharmacology

What synthesizes acetylcholine?

choline acetyltransferase enzyme

What synthesizes norepinephrine and epinephrine?

amino acid phenylalanine

What metabolizes acetylcholine?

acetylcholinesterase

What is another term for parasympathetic nervous system?

cholinergic

What is another term for sympathetic nervous system?

adrenergic

What is the preganglionic neurotransmitter for both PNS and SNS?

acetylcholine

What is the receptor for preganglionic neurotransmitter for both PNS and SNS?

nicotinic ACh receptor

What is the receptor for postganglionic neurotransmitter for PNS?

muscarinic ACh receptor

What is the receptor for postganglionic neurotransmitter for SNS?

norepinephrine adrenergic receptors (alpha and beta)

What is autonomic tone?

one branch of the autonomic nervous system is dominant and sets the tone of that tissue

What is a cholinergic drug?

compound that causes physiological responses to those of endogenous acetylcholine (cholinomimetic, parasympathomimetic)

What is a anticholinergic drug?

compound that decreases cholinergic nerve activity (anticholinergic, cholinergic blocking, parasympatholytic)

What is a direct acting parasympathetic drug?

mimic the action of acetylcholine

What is an indirect acting parasympathetic drug?

inhibit acetylcholinesterase

What are the main direct-acting cholinomimetic drugs?

Carbachol and Bethanechol

What is carbachol used for?

nicotinic and muscarinic receptor sites allow this to be used orally to improve GI motility in animals with intestinal or rumen impaction

What is bethanechol used for?

muscarinic receptor sites allow this to be used orally to improve contraction of urinary bladder; treatment of urinary retention and stimulates gastric emptying in foals and horses

What is the SLUD response?

salivation, lacrimation, urination, defecation

What is pilocarpine used for?

prevent synechiae (adhesions of iris to lens) during inflammation of anterior chamber; strong constrictor of pupil, and tear inducer

What do large doses of physostigmine do to the CNS?

first stimulate than depress (passes blood-brain barrier)

What is used to treat myasthenia gravis?

neostigmine, pyridostigmine, ambenonium (reversible inhibitors)

What are commonly seen in flea collars?

organophosphate compounds

What is pralidoxime (2-PAM)?

irreversible inhibitor commonly used with atropine to help cross BBB

What is cholinergic antagonists?

block the action of acetylcholine and prevent cholinergic action; anticholinergics, parasympatholytic

What are examples of muscarinic receptors antagonists?

atropine and scopolamine; prevent acetylcholine from binding to muscarinic receptor (competitive antagonist)

What originates from nightshade plant “belladonna alkaloid”?

scopolamine; dilate pupils

What do rabbits have that breaks down atropine and results in short half-life?

atropinase, atropinesterase

What is an essential antidote for organophosphates and overdoses of cholinergic (direct or indirect) agents?

atropine because inhibits muscarinic receptor to block parasympathetic response

What can be given to treat atropine toxicosis?

physostigmine can cross BBB and bind to acetylcholine or give emetics

What can be used as safer alternative to atropine?

glycopyrrolate does not penetrate BBB and is 2-4 times more potent making duration 4 time longer, less likely to induce tachycardia

What is N-butylscopolammonium bromide used for?

IV anticholinergic drug used to control abdominal pain associated with spasmodic colic; DON’T use with impacted horse that has glaucoma, yes it decreases GI motility but also decreases lacrimation and impairs drainage