Fig. 12. Model of transmitter and neuropeptide action on CPE cells. Binding of dopamine or TPep-NLS to a receptor leads to a reduction in I_Cl(Ca) and I_(Cl-)leak, leading to an increase in CBF. We hypothesize that I_(Cl-)leak is carried by the same CaCC channels as the I_Cl(Ca), thus a single action by dopamine or TPep-NLS will block both. The blockage of the Cl^- currents may lead to a depolarization of the cell, the signal necessary for Ca²⁺ influx. Pluses indicate molecules or actions that increase current size or beating rate, minuses represent inhibitory molecules or actions.