the effect of the k a current on inducement of seizures stephanie costa academy of notre dame

The Effect of the Ka current on inducement of seizures

Stephanie CostaAcademy of Notre Dame

Problem

Does the substitution of a Ka current, instead of a Hh current, in R15 pacemaker network

increase seizures in the brain?

Background Information• A seizure is the result of brain cells giving off more electrical energy

than can be handled by the brain.• Abnormal electrical impulses signal a seizure, among other brain

related issues. Abnormal electrical impulses can be seen in the data because the neurons do not follow the pattern of the R15 pacemaker neuron.

• Information travels through the brain by nerve impulses, chemical and electrical signals. The information goes through one neuron, across the synapse and then to the next neuron.

• Synapses are where two neurons meet, through this junction, cells communicate with each other.

• The R15 pacemaker is the neuron that sets the rate for all of the other neurons in that network.

Hypothesis

The Ka current will have an increased

probability of seizure occurrences than the regular Hh neuron structure, which will

not present any seizures.

Materials

• Computer• SNNAP (Simulator for Neural Networks and

Action Potentials) computer system

Procedure

• Build two neural networks, beginning with R 15 pacemaker neuron. One network will have a regular Hh (K channel) current and the other will have a Ka current.

• Each network will run over a course of 120 seconds.

• The conductance will be reduced from 2.0 to 1.0 at intervals of .1

• The output will be collected from each graph

K channel Ka channel

Variables

• Independent variable: The network that contains the Ka current

• Dependent variable: The output of the Ka current

• Controls: the Hodkin-Huxley model of the neuron

• Constants: the SNNAP program and the unaltered portions of the neuron/network

Hh model graphs

Hh 2.0

Hh 1.9 Hh 1.8

Hh 1.7 Hh 1.6

Hh 1.5 Hh 1.4

Hh 1.3 Hh 1.2

Hh 1.1 Hh 1.0

Ka model graphs

Ka 2.0

Ka 1.9 Ka 1.8

Ka 1.7 Ka 1.6

Ka 1.5 Ka 1.4

Ka 1.3 Ka 1.2

Ka 1.1 Ka 1.0

Conclusion

• The hypothesis was rejected. The Ka current had a decreased probability of seizures and actually inhibited seizures until a conductance of 1.6.

• A source of error could be the number of Ka or Hh channels in the network.

• Further research could include the results of extremes in the conductance level and the results of different neurons’ conductance when altered.

Works CitedBarnwell, L. F. S., Lugo, J. N., Lee, W. L., Willis, S. E., Gertz, S. J., Hrachovy, R. A., & Anderson, A. E.

(2009). Kv4.2 knockout mice demonstrate increased susceptibility to convulsant stimulation. Epilepsia, 50(7), 1741-1751. doi:10.1111/j.1528-1167.2009.02086.x

Brain. In Science online. Retrieved from http://www.fofweb.com/activelink2.asp?ItemID=WE40&SID=5&iPin=NS30825&SingleRecord=True

Norris, A. J., & Nerbonne, J. M. (2010, April 7). Molecular Dissection of Ia in cortical pyramidal neurons reveals three distinct components encoded by Kv4.2, Kv4.3, and Kv1.4 α-Subunit. The Journal of Neuroscience, 30(14), 5092-5101. doi:10.1523/JNEUROSCI.5890-09.2010

Panno, J. Neurons. In Science online. Retrieved from http://www.fofweb.com/activelink2.asp?ItemID=WE40&SID=5&iPin=NBCELL0008&SingleRecord=True

Sherwood, L. (2007). Principles of neural and hormonal communication. In P. Adams (Ed.), Human physiology: From cells to systems (6th ed., pp. 85-129). Thomson Brooks/Cole.

Sherwood, L. (2007). The plasma membrane and membrane potential. In P. Adams (Ed.), Human physiology: From cells to systems (6th ed., pp. 53-83). Thomson Brooks/Cole.

Simulator for Neural Networks and Action Potentials (SNNAP) (Version 8) [Computer software and manual]. (January 2003). Houston, Texas: The University of Texas-Houston Medical School.

(2008, August 18). Life Sciences; Research from National Cheng-Kung University, Department of Neurology provides new data about life sciences. Mental Health Weekly Digest, 78, Retrieved from http://elibrary.bigchalk.com