Mathematical Biology Seminar Steve Poelzing CVRTI, University of Utah Wednesday September 21, 2011 3:05pm in LCB 225 "Failures in Understanding Conduction Failure" Abstract: Organized electrical activity in the heart is synchronized through gap junction proteins called connexins. Pharmacologically blocking connexins slows cardiac conduction, but transgenically inhibiting connexins produces heterogeneous responses. Both interventions should increase the impedance between neighboring cells, and therefore it is unclear why different scientiests utilizing similar preparations arrive at very different conclusions with respect to the conduction-gap junction relationship. We are exploring the role of the extracellular space as a modulator of the conduction-gap junction relationship. We demonstrate that increasing the separation between cardiac myocytes increases the dependence of conduction on gap junction mediated conduction, while shrinking cellular separation has the opposite effect. These finding are interesting because it is counter to the predominant model of cardiac conduction. These finding are important because we now know that changes in connexin expression may not have any observable physiologic effect until the space between cells increase. In the case of increased extracellular volume and decreased gap junctions conduction failure is increased, which raises the chance of sudden cardiac death.