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

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

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

Staining for motor neurons was done with 1,1'- didodecyl 3,3,3',3-- indocarbocyanine perchlorate ( DiI)

Once the motor neurons were

identified, it was determined whether or not they are excitatory or inhibitory neurons.

This was done using

immunohistochemical staining for ChAT and NOS.

ChAT positive neurons are excitatory

overall NOS positive neurons are inhibitory

overall

 

Key Questions

1) What is the distribution of excitatory neurons like in the gastric region?

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

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

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

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

It is important to consider other

neurotransmitters also for a better overall picture

Why I chose this topic

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

1) Is it possible to alter the levels of ChAT and NOS in the digestive tract?

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

http://www.youtube.com/watch?v=oLSmNcem2X0

Works cited

Citation: http://ski.clps.brown.edu/cogsim/

cogsim.3nets.prt.pdf http://www.ncbi.nlm.nih.gov/pmc/articles/

PMC1484078/pdf/biophysj00727-0011.pdf http://scholar.google.com/scholar_url?

hl=en&q=http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1484078/pdf/biophysj00727-0011.pdf&sa=X&scisig=AAGBfm3mfrF5fJirZdCccPO-ywN8hot4Gw&oi=scholarr

http://invibe.net/biblio_database_dyva/woda/data/att/731d.file.03776.pdf

Thank you