1. ACETYLCHOLINE SIEGEL CHAPTER 13 COOPER CHAPTER 7 (RESERVE) SIEGEL CHAPTER 12 (RECOMMENDED)

2. Acetylcholine Intro to chemicals used as NT Ach History Distribution
Functions
Synthesis
Storage
Release
Inactivation

3. TRANSPORT AND
UPTAKE INTO VESICLES
SYNTHESIS
RELEASE
Life cycle of
neurotransmitters
DEGRADATION
OR RE-UPTAKE
POST-SYNAPTIC
RECEPTORS

5. BIOGENIC AMINE, SUBSTITUTED AMMONIA. Ach identified in 1929 at the NMJ.

7. Structure-function relationships are not always clear, but note the size of the antagonists. This may contribute to their ability to block agonist binding.

8. Loewi Experiment: ‘vagusstuff’
First evidence for an active secreted substance, 1921.

9. Ach in the PNS
Ach is responsible for all motor transmission in vertebrates
Ach mediates parasympathetic actions of the autonomic nervous system
Ach is produced in just about all living things from bacteria, fungi, to plants and mammals.

10. Ach is released from pre-ganglionic fibers originating in the CNS and post-ganglionic fibers originating in the PNS, which mediates the relaxing functions of the Parasympathetic branch of the autonomic NS

11. Lesion tracks, measure Ach levels
Antibody staining to Ach synthetic enzymes.

12. Functions of Ach in the CNS
Basal Forebrain: arousal and attention
Learning and memory?
Alzheimer Disease
Parabrachial nucleus: REM sleep
Continue to fire during REM
# cells correlate with REM sleep
Reward and Addiction (striatum?)
Pain and other sensory input

13. Functions of Ach in the PNS

14. Ach at the NMJ
Regulated release of Ach causes muscle depolarization: mEPP or EPSP
Contraction of muscle
Increase Ach release, duration, receptor activation?
Decrease Ach release, duration, receptor activation?

15. Synthesis of Ach
ChAt
Chat synthesized in cell body but transported to terminal where highest synthesis of Ach takes place.
Cytoplasmic 69kD form=80-90% of activity
Nuclear 82kD form

16. Genetic locus for ChAt
The gene encoding VAChT is embedded in the first intron of the gene encoding ChAT—possible co-regulation of expression of the two related genes.

17. * Source of substrates for Ach synthesis
ACoA—derived from glucose via pyruvate produced during glycolysis.
Choline—50-60% is recycled from Ach, other from diet, but not easily transported across BBB

18. CHT is critical for survival
CHT knockout animals die within an hour of birth. Demonstrates the importance of choline recycling and Ach production in general.

19. Ideas about CHT regulation

20. Coupling Ach release to Ach synthesis to maintain pool
Critical slide! More data in graph reading lecture next week.

21. Ach equilibrium
Ach levels are extremely stable over a wide range of neural activity
(choline)+(AcCoA) Ach + (CoA)
Availability of choline (CHT) drives rxn to the right
Decrease in Ach will cause shift in equilibrium (no substrate for reverse rxn)

22. Synaptic vesicles assembled in the nerve terminal
V-ATPase sets up gradient used by VAchT to import Ach into vesicles. Protons into vesicle by ATPase, then 2 protons pumped out for every Ach pumped in.

23. Ach release
Action potential arrives at pre-synaptic terminal, depolarizing membrane
Ca2+ must be present for Ach to be released and have any effect

24. Ca2+ is required for PSP
Post-synaptic
responses
Current in pipet:

25. Dynamics of potential changes at the synapse
Same essential result, just looking at temporal relationships (squid).
Major delay: Ca channels opening in the presynaptic terminal
Small delay: Ca influx to post synaptic response

26. Other factors that affect Ach release
Trophic factors
NGF exerts rapid short term effects on Ach synthesis and release
More data on this next week
Estrogen (other hormones?)

27. Estrogen increases ChAt levels

28. Acetylcholinesterases
Critical for recycling choline-near perfect
Limits receptor signaling events/duration
Found in extracellular space, synaptic cleft: not a marker of cholinergic cells
Inhibitors of AchE
Alzheimer disease (aricept)
Glaucoma, myasthenia gravis
Bioterrorism
Effect on Ach??
Unusual—all other transmitters use reuptake to terminate transmission. May exist due to need to tightly regulated muscle contractions for purposeful movement.