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CHARACTERIZATION OF
EXCITATORY AND INHIBITORY
MOTOR NEURONS TO THE
HUMAN GASTRIC CLASP AND
SLING FIBERS
By Nasser Khan
IMPORTANT: KEY TERMS TO KNOW
BEFORE WE GO THROUGH THIS
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Motor neurons: Neurons that convey impulses from the CNS to muscles, glands, and
other effector tissues.
Inhibitory neurons: Neurons that evoke excitations of their target neurons.
Excitatory Neurons- Neurons that evoke excitations of their target neurons.
Lower Esophagus- Anatomical structure of the stomach attached to the esophagus.
Sphincter- An anatomical structure, a circular muscle that normally maintains the
constriction of a body passage, and relaxes as required by normal physiological
functions.
Sling fibers- Comprise the long oblique gastric fibers on the greater curvature side
of the stomach
clasp fibers- Comprise the thickened inner circular muscle layer adjacent to the
lesser curvature
Acetylcholine- Excitatory neurotransmitter. Cholyne Acetyltransferase (ChAT) is
involved in its synthesis
Nitric Oxide- Inhibitory neurotransmitter, formed through the help of Nitric Oxide
Synthase (NOS)
Purpose of Research
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The purpose of this study was to identify the position of and
characterize excitatory and inhibitory motor neurons in the human
gastric sling and clasp fibers, their location, structure, responses, and
how they affect that area of the body and potential complications
that may arise there.
Often times, there is a discrepancy with the cell signaling that takes
place within the gastric clasp, that is to say the proper motor
neurons, (which are peripheral) are not activated or synthesized
because the desired neurotransmitter does not reach the nerve
terminal, and this can result in severe gastrointestinal issues, such as
acid Reflux or Achalasia. That is why it was important for
researchers to see how much of what type of neuron was present in
the gastric clasp and sling fibers; this knowledge could help fight off
illnesses that arise there, such as the latter.
Key Concepts
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Staining for motor neurons was
done with 1,1'- didodecyl 3,3,3',3-indocarbocyanine perchlorate ( DiI)
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Once the motor neurons were
identified, it was determined
whether or not they are excitatory or
inhibitory neurons.
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This was done using
immunohistochemical staining for
ChAT and NOS.
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ChAT positive neurons are
excitatory overall
NOS positive neurons are inhibitory
overall
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Key Questions
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1) What is the distribution of excitatory neurons like
in the gastric region?
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2) What is the distribution of the inhibitory neurons
like in the gastric region?
3) Are there more excitatory or inhibitory neurons
in the gastric region?
Significant Points and assumptions
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Excitatory signals (which are mediated via acetylcholine) to the
motor neurons of the gastric muscle fibers cause the muscles to
contract.
This physiological function is significant primarily because it helps
prevent complications such as the reflux of acid or food, and also
carries out the proper digestion and ingestion of nutrients.
Inhibitory signals ( which are mediated via nitric oxide) to the motor
neurons of the gastric muscle fibers cause the muscles to relax.
This is physiologically significant because it allows food to pass
through properly, without incurring a backup.
In the event the sphincter and surrounding muscles can not relax,
there may be complications such as achalasia.
Conclusion and knowledge gained
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Most of the motor neurons in the sling fibers were
found to be ChAT positive, and therefore excitatory
Most of the motor neurons in the clasp fibers were
found to be NOS positive, and therefore inhibitory
Overall, most of gastric region motor neurons were
found to be EXCITATORY, since the majority of the
neurotransmitter detected via retrogradive labeling
was chAT, the enzyme that synthesizes acetylcholine
at the neural terminal.
Possible Bias
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Limiting the excitatory neurons to only ChAT
positive neurons might have some bias
Limiting the inhibitory neurons to only NOS positive
neurons might limit the importance of the overall
conclusion that most of the neurons in the gastric
region are excitatory
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It is important to consider other neurotransmitters
also for a better overall picture
Why I chose this topic
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Gastro Intestinal issues constitute an important sub
discipline within the respected fields of biology and
medicine. Neurology essentially affects the entire
human body and the processes therein, giving it the
distinction of a “systemic science”. As a result, they
are both going to have significant effects on one
another. This study combined these two important
disciplines, and consequently caught my attention.
Questions I have
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1) Is it possible to alter the levels of ChAT and NOS
in the digestive tract?
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2) How can the results of this experiment be used
for therapy of patients suffering from GI issues?
3) Does the overall composition of excitatory vs
inhibitory neurons change with one's age? Does it
change with obesity?
Video/ Visual
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http://www.youtube.com/watch?v=oLSmNcem2X0
Works cited
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Citation:
http://ski.clps.brown.edu/cogsim/cogsim.3nets.prt.pdf
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC148407
8/pdf/biophysj00727-0011.pdf
http://scholar.google.com/scholar_url?hl=en&q=http:/
/www.ncbi.nlm.nih.gov/pmc/articles/PMC1484078/pd
f/biophysj007270011.pdf&sa=X&scisig=AAGBfm3mfrF5fJirZdCccPOywN8hot4Gw&oi=scholarr
http://invibe.net/biblio_database_dyva/woda/data/
att/731d.file.03776.pdf
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Thank you