pharmacology 6 - autonomic ns Flashcards
co-transmission….what is it? what is special about dopamine?
involves other neurotransmitters eg. GABA (CL-) dopamine (precursor of NA and also a transmitter itself) NO, NPY, VIP, substance P.
what is the enteric nervous system? where?
intrinsic nerve plexuses of the GI tract. cell bodies are in interstitial wall. PNS and SNS modulate it. many neuropeptides have an effect - eg. serotonin
what are the 9 ways that drugs can act on the PNS/SNS system. ?
- efefct synthesis of NT
- compete for the same metabolic pathway
- block reuptake of the precursors eg. tyrosine, choline.
- displace the NT
- block the release of the NT
- act as an agonist to receptors
- act as an antagonist
- block transport and affect storage
- inhibit the degradation (not removed and so stays high) eg. achei
3 classes of PNS drugs? what do they act on primarily?
- muscarinic agonists
- achei - stops breakdown of ACH)
- muscarinic antagonists
these all act on the postsynaptic PNS nerve terminal as nicotinic would also affect the SNS.
2 classes of muscarinic agonists? what is their action?
- synthetic choline esters/ach
- naturally occuring alkaloids.
they are parasymoathomimetics.
choline esters are what? what do they do? eg’s? what is different about carbacol? what is their topical use?
they are muscarinic agonists. they mimic the PNS.
bethanecol, carbacol, methacholine
slowly degraded by ACHE. affect the CVS. ( slow the HR reduce force and speed etc. ) they also cause vasodilation.
resistant to ACHE. also affect the GI tract (increased)
carbacol also has some nicotinic action?
topically used for miosis!!
cholinomimetic alkaliods are what? eg? what do they do? what is galucoma and how do they help?
they are muscarinic agonists. eg. pilocarpine.
topically to eye for miosis.
treat glaucoma!!…..increased intraocular pressure esp. dogs. durg can open up the drainage angle and also reduce the amount of aqueous humour by doing this therefore….reduce pressure within the eye.
what are ACHEI? what is their effect? 2 types? eg of very bad one used in country?
Acetylcholine esterase inhibitors. can be reversible or irreversible. they cause an increased amount of ACH at receptors.
sarin gas used in syria is non-reversible.
what are the factors of toxicity of ACHEI?
volatility and solubility. - how easily A and E. whether they are reversible or irreversible.
what are the uses of ACHEI? eg of one? diagnose what ? what is myasthenia gravis? edrophonium chloride, neostigmine, pyridostigmine
cause mydriasis of the eye. contract muscle. increase heart rate etc and reduce GI tract.
edrophonium chloride: reverse muscle relaxants
diagnose myasthenia gravis. rapid onset and short duration, give by slow I/V injection.
Neostigmine: moderate duration reverse muscle relaxants treat myasthenia gravis oral or i/v TID orally - but taylor.
pyridostigmine: moderate action
treat myasthenia gravis
orally BID
i/v half life = shorter (2hrs)
myasthenia gravis = congenital (not enough receptors - reduce muscle movement)
immune mediated = little exercise tolerance, increase ach to diagnose and should improve.
ACHEI - toxicity? increased ACH? WHAT WOULD HAPPEN AND WHAT COULD YOU TREAT IT WITH?
salivation, muscle tremors, defeacation, miosis, collapse by lowered HR, lowered BP, lowered CO. vasodilation.
use atropine to reverse it (antagonist) - used to treat in syria as reduces ACH.
what do muscarinic antagonists do? what kind of antagonists? why no efficacy? eg’s?
parasympatholytics. competitive antagonists for ach.
no efficacy as bulkier aromatic group.
eg. atropine and scopolamine. (pupils dilate)
what does atropine do? what is it used to treat? why dont use in horse? SIDE EFFECTS? what can be used for toxicity.
lowers ach. given i/v, i/m, s/c, p.o.
metablosied in liver and excreted by kidney.
ionised so crosses into the CNS.
used as pre-med to decrease salivation.
dont use in horse as GI recued and central excitation. lowered secretion too. dilate pupils. increases HR. act against ACHEI.
side effects: CNS stimualtion constipation tachycardia urinary retention ACHEI can also be used to treat toxicity!!
scopolamine does what? what is it? eg’s? glycopyrronium bromide, ipratopium bromide, cyclopentoalte?
drys secretions, reduce Gi tract contractility. antiemimetic properties.
glycopronium bromide: does not cross BBB/placenta. (wont cause abortion) less CNS effects use in c-sections less tachycardia ocular surgery (dilate)
ipratopium bromide: bronchdilates RAO. in horses. given by inhalation so no other side effects.
cyclopenolate: mydriatic long duration and helps with ureitis. its relaxs the ciliry mm that suspends iris.
