Block 1 Autonomics Flashcards
Primary NTs in autonomic and somatic NS
ACh, NE, epi (adrenal)
Direct acting drugs
Activate or block receptors directly
Cholinergic receptor types & locations
Muscarinic - neuroeffector junctions
Nicotinic - all autonomic ganglia and somatic NMJ
Sympathetic NTs
Pregang: ACh -> nicotinic
Postgang: NE -> adrenergic, ACh -> muscarinic (sweat glands)
Parasympathetic NTs
Pregang: ACh -> nicotinic
Postgang: ACh -> muscarinic
Somatic NTs
ACh -> nicotinic
SNS location, length & ratio of fibers, discharge pattern
Thoracic, lumbar region SC; short pre-gang, long post-gang, low pre to post ratio; unit discharge = diffuse activation targets
PSNS location, length & ratio of fibers, discharge pattern
Cranial, sacral SC; long pre-gang, short post-gang, high pre to post ratio; can discretely activate targets
Baroreceptor reflex & importance for BP drugs
Stretch receptors (aortic arch, carotid sinus) w/ inc arterial pressure -> brain stem VMC -> vagal dec heart rate (reflex bradycardia) *Drugs affecting BP can cause reflex brady- or tachycardia
Vesamicol & Botulinum toxin
V: blocks ACh/H+ exchange so no ACh in vesicles
B: blocks ACh vesicle fusion/release
AChE inhibitor & Hemicholinium
I: blocks ACh breakdown to choline + acetate by AChE on post-syn neuron
H: blocks choline/Na+ cotransport back into pre-syn neuron
Muscarinic receptor subtypes
M1 - CNS and autonomic ganglia
M2 - cardiac muscle
M3 - SM and glandular tissue
M4, 5 - CNS
Muscarinic receptor effects on: heart SA and AV nodes, blood vessels, GI, iris, ciliary mm, bladder, lung, exocrine glands
SA: bradycardia
AV: slow conduction
BV: vasodilation
GI: increased tone, secretions, sphincters relax
Iris: miosis (contraction)
CM: accommodation (contraction)
UB: detrusor contraction, sphincter relaxes
Lung: bronchi contract, increase secretions
Glands: increase tears, sweat, saliva
Nicotinic receptor effects on ganglia, adrenal medulla, skeletal muscle
Gang: at high doses -> SNS and PSNS responses
AM: release epi and NE
SkM: depolarization of end plate
Types of cholinergic receptor agonists and antagonists
Ag: direct-acting, indirect-acting reversible, indirect irreversible
Ant: muscarinic, nicotinic
Main types of direct and indirect cholinergic receptor agonists
Direct: choline esters (highly polar 4’ amines), plant alkaloids (lipid soluble)
Indirect: reversible and irreversible cholinesterase inhibitors
Acetylcholine
Choline ester, short duration, nonselective, no therapeutic use
Methacholine
Choline ester, muscarinic, longer duration than ACh
Carbachol
Choline ester, predominantly nicotinic, topical agent for glaucoma
Bethanechol
Choline ester, predominantly muscarinic, to stimulate bladder/GI without cardiac effects
Muscarine
Plant alkaloid, from poisonous mushrooms
Nicotine
Plant alkaloid, from tobacco; oral, nasal, transdermal for smoking cessation
Pilocarpine
Plant alkaloid, from a small shrub, predominantly muscarinic, topical agent for glaucoma, oral agent for xerostomia
Cevimeline (Evoxac)
Synthetic direct cholinergic agonist for xerostomia, dry eyes after radiation or Sjogren’s syndrome
Primary open angle glaucoma & treatment
Inc intraoc pressure due to narrowed ant chamber angle, decreased aq humor outflow -> optic nerve damage
Tx: inc AH outflow w/ PG analogs, muscarinic receptor agonist; dec AH production w/ a2 agonists, beta antagonists, carbonic anhydrase inhibitors
Neostigmine
Indirect reversible chol inh, 4’ amine - poor CNS penetration, antidote for NMJ blocking-drugs like d-tubocurarine
Contra: GI/bladder obstruction, asthma
Edrophonium (Tensilon)
Neostigmine analog with shorter duration of action
Physostigmine
Indirect reversible chol inh, 3’ amine - can penetrate CNS, alkaloid from alabar bean
Myasthenia gravis & treatment
AI ab’s against nicotinic receptor in skm -> weakness
Edrophonium - to diagnose MG
Tx: neo-, pyridostigmine
Donepezil (Atricept)
Once daily reversible chol inh for dementia/AD a/w dec ACh production in brain; high doses can cause adverse effects (GI, bladder fxn, dec heart rate)
Galantamine (Rizatidine)
Reversible chol inh for dementia/AD a/w dec ACh production in brain; high doses can cause adverse effects (GI, bladder fxn, dec heart rate)
Rivastigmine (Exelon)
Reversible chol inh for dementia/AD a/w dec ACh production in brain; high doses can cause adverse effects (GI, bladder fxn, dec heart rate)
Examples of irreversible chol inh
Organophosphates (pesticides, sarin gas), malathion
Signs and symptoms of organophosphate toxicity
Musc: bradycardia, hypotension, salivation, sweating, lacrimation, miosis
Nic: muscle fibrillation, fasciculation, paralysis
CNS: confusion, ataxia, coma, resp paralysis
SLUDGE: salivation, lacrimation, urination, diarrhea, gastric emptying
Muscarinic receptor antagonists
*Most common cholinergic drug aka “anticholinergic”, most are competitive antagonists
Belladonna alkaloids, semi- and synthetic antagonists
Nicotinic receptor antagonists
Ganglionic blocking agents, non depolarizing and depolarizing neuromuscular blocking agents
Atropine
Belladonna alkaloid anticholinergic, widely distributed, T½ 2 hours, blocks M1,2,3; for sinus bradycardia, chol inh overdose antidote
Scopolamine
Anticholinergic plant alkaloid; greater CNS effects than atropine, isolated from henbane; for motion sickness
Anticholinergic response from eye, sweat, secretions, lungs, heart, GI, bladder
Eye: mydriasis, no accommodation Sweat: blocked, inc body temp Sec: drying (*COPD) Lungs: bronchodilation, reduced secretions Heart: increased rate GI: decreased motility UB: atony, urinary retention
Hyoscyamine
L isomer of atropine, for GI spasms
Belladonna alkaloid toxicity profile
Tox: dry mouth, blurred vision, tachycardia, palpitations, urinary retention, delirium, hallucinations
Belladonna alkaloid relative contraindications
Glaucoma, prostatic hyperplasia, dementia, delirium