Cardiovascular disease, be it coronary heart disease or heart attacks, is the number one cause of death in the United States. In fact, one person dies every 37 seconds from cardiovascular disease. Now, neural circuits are being studied to understand their functions in relation to cardiovascular diseases. Intracardiac neurons are part of a circuit that acts as an intermediary between the vagus nerve and cardiac function. Identifying the role of ion channels in the intracardiac nervous system (ICN) is key to understanding the relationship between the ICN and electrical activity in the heart. Specific ion channels have been previously identified as vital to electrical conductivity in many areas throughout the body. Assuming these ion channels exhibit similar functions in the heart, the ICN can be studied for the expression of genes that encode for their purpose. We explored that if different samples of cells from a rat ICN and their level of certain gene expression for ion channels are assessed with respect to their location, then a connection can be identified between the location of the certain gene expression and their function. By analyzing gene expression profiles from many single neurons and statistical data in the rat ICN, two families of genes were identified that exhibited unique properties concerning the sinoatrial node and were functionally related to electrical activity within the body. It is the goal to understand how an alteration in this circuit can cause differences in cardiac function (Armour, 2007).