Figure 4. Relation between maximum diastolic potential (MDP) and maximum rate of phase 0 depolarization (Vmax) of Purkinje fiber action potentials at 37 degrees Celsius and at 30 degrees Celsius during the gradual increase in external [K sup +]([K sup +]o) from 0.8 to 10 mM. *P < 0.05 MDP or Vmaxversus lower [K sup +]o. *P < 0.05 MDP37degrees Celsius versus MDP30degrees Celsius at same [K sup +]o.