Available at: http://digitalcommons.calpoly.edu/theses/645
Date of Award
MS in Biomedical Engineering
Biomedical and General Engineering
There are forty registered organophosphates in the United States and they range from pesticides and insecticides to nerve agents or neurotoxins such as sarin. Organophosphates (OP’s) have been used in chemical warfare for years and tend to lead to death due to an attack on the nervous system. Chemical assays and mass microscopy have been used to assess the concentration of OP’s in the environment, but both methods require the body to metabolize the OP first, which can be detrimental to the victim. It is crucial to come up with a method to investigate and detect these neurotoxins without causing harm first.
There have been several studies presented in the literature that use medicinal leeches and sharp electrode electrophysiology to study the function of the motor end plate. Kuffler, Potter and Stuart have all conducted studies using the medicinal leeches to do so. They mapped out the cells within the leech ganglion as well as created an atlas of the entire leech anatomy, and demonstrated the electrical connection between the motor neuron and longitudinal muscle fibers. Using the knowledge they have provided, a medicinal leech and sharp electrode electrophysiology can be used to investigate the effects of organophosphates on the nervous system. Before this can be achieved a dissection preparation must be implemented that can be utilized in electrophysiological experiments and that demonstrates the electrical connection between the motor neuron and muscle fibers.
This thesis outlines the implementation of the medicinal leech dissection preparation described above. The preparation removes one ganglion from the leech, leaving the roots attached to the portion of the muscle wall it innervates. To demonstrate the preparations validity, sharp electrode electrophysiology is performed using a current clamp and discontinuous single electrode voltage clamp (dSEVC). A current pulse stimulates the motor neuron and a voltage recording is obtained from the ganglion as well a current recording from the muscle wall. The electrical connection is therefore demonstrated. This dissection preparation and electrophysiology experiment are written up in a procedural manner so that another individual could repeat the experiment. The next logical step would be to use these procedures to perform OP nerve agent experiments to investigate the effect of OP’s on the neuromuscular junction.