This presentation provides an overview of agents that inhibit acetylcholinesterase. This lecture was delivered to 2nd year pharmacy students enrolled in a pharmacology & toxicology course and accompanies chapter 10 of Goodman & Gillman (12e).

1. Anticholinesterase Agents
Brian J. Piper, Ph.D., M.S.

2. Goals
• Synthesis & Breakdown of Acetylcholine
• Therapeutics & Toxicology

3. Dietary Sources of Choline
http://lpi.oregonstate.edu/infocenter/othernuts/choline/

4. Biosynthesis of Acetylcholine
ACh: Acetylcholine
AcCoA: acetyl coenzyme A
CAT: choline acetyltransferase
Stahl (2008). Essential Psychopharmacology. p. 914.

5. Stahl (2008). Essential Psychopharmacology.

6. Anatomy of cholinergic pathways
• Nucleas basilis (Basal Forebrain): connections to
frontal cortex, important for cognition
• Caudate-Putamen: important for motor function
Meyer & Quezner (2001). Psychopharmacology.

7. Acetylcholine (ACh) in PNS
Receptors
N: Nicotinic
M: Muscarinic
Katzung et al. (2012). Basic & Clinical Pharmacology. p 80.

8. Acetylcholine Breakdown
BuChE: butyrylcholinesterase (pseudo), liver,
plasma
VAChT: Vesicular Acetylcholine Transporter
See also Animation:
Cholinergic Neuroeffector Junction
Stahl (2008). Essential Psychopharmacology. p. 915.

9. Oneata Gorge, OR
Acetycholinesterase (AChE) Gorge
Structure
Colombia River
Acyl Pocket (AP):
Pheylalanine 295 & 297
Choline Subsite (CS):
Tryptophan 86
CS Glutamic Acid 202
Tyrosine 337
AP CT Catalytic Triad (CT):
Glutamic Acid 334
Histidine 447
Serine 203 (phophorylation)
Bourne et al. (1995). Cell, 83, 493-506.

10. Acetycholinesterase
Gorge Structure
PBS
Acyl Pocket (AP):
Choline Subsite (CS):
Catalytic Triad (CT):
CS
Peripheral (Rim) Binding Site (PBS):
Tryptophan 286
AP CT Tryptophan 124
Tryptophan 72
Bourne et al. (1995). Cell, 83, 493-506.

11. Physostigmine
• Found in seed (Calabar bean) of African plant Physostigma
venenosum
• Reversible acetylcholinesterase inhibitor
• Ordeal Poison: accusation of demonic possession
– Winner: vomited (or didn’t chew beans)
– Loser: miosis, excessive salivation, decreased
bowel/bladder control, seizures, asphyxiation!
• Used for glaucoma & belladonna overdose
Pronunciation: http://dictionary.reference.com/browse/Physostigmine?s=t

12. Sarin (GB)
• Colorless, odorless, liquid named after
German scientists (Schrader, Ambros,
Rudinger & Van der LINde) in 1938
• Used in Subway Sarin Incident of 1995 (killed
13, injured 50)
• Inhalation & skin absorption

13. Pesticides
• herbicides (plants), fungicides, pediculicides (lice),
acaracide (ticks & mites), biocides
(microorganisms), rodenticides
• Insecticides
– Organophosphates (malathion): long-acting,
irreversible, phosphorylate active site
– Carbamates: short-acting, reversible, carbamylation of
active site
– “One-million people are poisoned by ACh-E inhibitor
insecticides and several hundred thousand die” (world-
wide)
Gupta et al. (2012). Organophosphate and carbamate pesticides. In Reproductive Toxicology.

14. Organophosphate Pesticide (OP)
http://depts.washington.edu/opchild/acute.html

15. Chyka (2008). Clinicical toxicology. In Pharmacotherapy: A Pathophysiological Approach.

16. Antidote(s) to Acetycholinesterase
Inhibitors
• Atropine: mACh antagonist
• Diazepam: GABAA allosteric modulator, seizures
• Reactivators: attach to inhibitor & separate inhibitor
from acetylcholinesterase (dephosphorylate)
– Examples: pralidoxime (2-PAM), HI-6
– Concern: not one reactivator for all AChE-Inhibitors
Bagjar (2010). Acta Medica, 53, 207-211.

17. Myasthenia Gravis
• Autoimmune disorder caused by antibodies against nicotinic
Acetycholine receptors
• Therapies include 1) neostigmine & pyridostigmine; 2)
immunosuppresive; 3) thymectomy
Ptosis (toe sis)
0:00 to 0:45 with Jade: http://www.youtube.com/watch?v=XdpW5RMp-T0

19. Alzheimer’s Disease (AD)
• Neurodegenerative disease
• Nucleas basilis is one region affected early
• AChE Inhibitors may provide some
symptomatic improvement
– Tacrine: short acting, infrequently used
– Donepezil: long acting, commonly used

20. Stahl (2008). Essential Psychopharmacology. p. 921.

21. Stahl (2008). Essential Psychopharmacology. p. 922.

22. Alzheimer’s Disease Assessment Scale:
Cognitive
• Word Recall: memorize list of words for
immediate recall
• Orientation: name, day of week, year, place
• Praxis: copy geometric pattern
• Word Recognition: get list (A), differentiate A
from other words (B)

23. Subtle Benefits for AD
• Multi-site (23) randomized,
controlled trial (N=468/273)
for 3 months.
• ADAS-Cognitive is clinician
rated measure of memory, ---------------------------------------
language, and movement (max
score = 70).
• Adverse effect (sweating,
↑micturition) were 34%
(placebo) versus 51% (Tacrine)
Farlow et al. (1992). JAMA, 268(18), 2523-2529.

24. Organophosphates & ADHD?
• Parents of nationally representative sample of children
were interviewed for symptoms of Attention Deficit
Hyperactivity Disorder (ADHD) using the Diagnostic
Interview Schedule for Children (DISC)
• Child urine was analyzed for levels of organophospate
metabolites (DEAP & DMAP)
• Odd’s Ratio: 1.0 events equal, <.5, >1.5 statistically sig
Bouchard et al. (2010). Pediatrics, 125(6), e1270-1277.

25. Refresher on Goodwin Terminology I
(p. 185-194)
antiporter (p. 187): protein that moves two different molecules (e.g. ions) in opposite
directions across a plasma membrane
satellite cells (p. 189): small progenitor cells found in muscle
plexus: intricate network (nerves or blood vessels)
myenteric plexus (p. 189): plexus of unmyelinated fibers and postganglionic
autonomic cell bodies found in the muscular coat of the esophagus, stomach, &
intestines
miosis mydriasis

26. Refresher on Goodwin Terminology II (Chapter 10)
reversible enzyme inhibitors (p. 239): molecules that bind to enzymes weakly (non-covalent bonds)
irreversible enzyme inhibitors (p. 239): molecules that bind to enzymes strongly with covalent bonds
Edrophonium (p. 241): reversible acetylcholinesterase inhibitor, used to differentiate myashthenia gravis from a
cholinergic crisis
schistosomias (p. 245): disease caused by parasitic worm (Schistosoma), associated with unsanitary H2O
conjunctiva (p. 246): mucous membrane that covers eyeball
achalasia (p. 246): inability of muscle to relax
atony (p. 246): lack of tone, muscular weakness
antidromic (p. 246): conduction of nerve impulse in the direction opposite of the usual one
fasciculation (p. 246): small, localized, involuntary muscle contraction
hypoxemia (p. 246): deficiency of oxygen in arterial blood
alkyl: carbon and hydrogen
ureter (p. 246): duct conveying urine from kidney to bladder
alkoxy group (p. 249): alkyl group singly bonded to an oxygen
stoichiometry (p. 249): branch of chemistry that deals with relative quantities of reactants & products in
chemical reactions
pesticide: substance intended for preventing, controlling, or destroying any pest including herbicides (plants),
fungicides, pediculicides (lice), biocides (microorganism), & rodenticides
dysuria (p. 250): painful urination
esters: chemical compounds consisting of a carbonyl (C=0) adjacent to an ether (R-O-R’)
salutary (p. 246): favorable to or promoting health

27. Alzheimer’s Disease Assessment Scale: Cognitive
Schultz et al. (2001). Braz J of Med & Bio Res, 34, 1295-1302.